Gary L. Miller and Ariel E. Lugo

June 2009
Authors

Gary L. Miller is a professor, University of North Carolina, Environmental 

Studies, One University Heights, Asheville, NC 28804-3299. Ariel E. Lugo is 

the Director of the U.S. Department of Agriculture, Forest Service, International

Institute of Tropical Forestry, Jardín Botánico Sur, 1201 Ceiba Street, Río Piedras,

PR 00926-1115. 

The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of 

multiple use management of the Nation’s forest resources for sustained yields of wood, water,

forage, wildlife, and recreation. Through forestry research, cooperation with the States and 

private forest owners, and management of the National Forests and national grasslands, it

strives—as directed by Congress—to provide increasingly greater service to a growing Nation.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and

activities on the basis of race, color, national origin, age, disability, and where applicable sex,

marital status, familial status, parental status, religion, sexual orientation genetic information,

political beliefs, reprisal, or because all or part of an individual’s income is derived from any

public assistance program. (Not all prohibited bases apply to all programs.) Persons with 

disabilities who require alternative means for communication of program information (Braille,

large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice

and TDD).To file a complaint of discrimination, write USDA, Director, Office of Civil Rights,

1400 Independence Avenue, S.W. Washington, DC 20250-9410 or call (800) 795-3272 

(voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.
Abstract

Miller, Gary L.; Lugo, Ariel E. 2009. Guide to the ecological systems of

Puerto Rico. Gen. Tech. Rep. IITF-GTR-35. San Juan, PR: U.S. Department of

Agriculture, Forest Service, International Institute of Tropical Forestry. 437 p. 

This guide is an introduction to the ecological systems of Puerto Rico. It covers the

diversity of ecological systems in the island, their most common plant and animal

species, and salient aspects of their structure and functioning. Terrestrial, wetland,

coastal, and marine ecosystems are included, as well as agroforest and urban systems. The discussion of the ecological systems of Puerto Rico is presented in the

historical, cultural, and natural disturbance regime of the Island. In addition, we

discuss the environmental infrastructure and organizations responsible for the 

conservation of Puerto Rico’s natural resources, and provide useful information to

facilitate field visits to representative examples of the Island’s ecological systems.

Keywords: Ecological systems, rain forests, dry forests, tropical forests, coral

reefs, estuaries, mangroves, seagrasses, Puerto Rico.
Preface

This publication arose as a result of a series of field trips conducted in Puerto Rico 

by Gary L. Miller and Ariel E. Lugo with students on courses in tropical ecology 

at various Puerto Rican and U.S. colleges and universities. The field trips in many

cases were preceded by semester-long lecture courses with field courses varying in

length from a few days to 4 weeks. Through the years, a variety of handouts have

been prepared describing many of the topics covered in this publication. The

amount of literature centered on Puerto Rico and the Caribbean has grown tremendously in the last two decades. Because these courses were geared toward undergraduates, however, much of the technical literature was too voluminous and, in

some cases, too technical for a lay audience. In response, this book was written to

include a mixture of technical and applied information that a diverse reading audience might find ecologically informative and generally interesting. It covers most

of the important ecological systems, a selected group of species, and some of the

important environmental issues confronting Puerto Rico and the Caribbean today.

Although most of the technical publications and data sets cited were derived from

studies conducted in Puerto Rico, much of what is generally described in terms of

ecosystems and species is typical of most islands in the Caribbean. Clearly there is

much variation from island to island in regard to size, soils, topography, altitude,

rainfall, and accessibility. There is, however, considerable overlap in species and

ecosystem presence. In addition, all of the Caribbean islands are experiencing similar problems related to expanding human populations, providing environmentally

based amenities, protecting species and habitats; environmental catastrophies such

as hurricanes, landslides, and floods; and loss of their fisheries owing to overfishing. For these reasons, this guide is relevant throughout the Caribbean region.

In addition, useful and practical information, such as the location of habitats for

field trips, references to environmental agencies, field trip checklists, videotapes,

maps, and guides to Puerto Rico has been provided in appendix 2. For those wanting more technical information, many citations to recent technical literature are

provided in each section. The material is meant to be used according to areas of

interest, and for this reason, we allow some redundancy among sections. We hope

this publication will provide a better fundamental knowledge of the environmental

conditions of Puerto Rico and the Caribbean.
Contents

1 Chapter 1: Overview of Puerto Rico

1 Introduction

4 Puerto Rico—Its History, Politics, and Economy

4 Early History

7 The Colonial Period

8 Steps Toward Autonomy

8 The American Period

12 Contemporary Puerto Rico

18 Physical and Climatic Zones of Puerto Rico

18 Geography

20 Climate

21 Hurricanes

23 Geology

25 Soils

27 Chapter 2: Flora and Fauna of Puerto Rico and the Caribbean

27 General Review of the Flora

33 Trees

36 General Review of the Fauna

52 Tree Frogs 

55 Birds 

58 Neotropical Migrants 

63 Bats

67 Termites

70 Endangered Species 

79 Chapter 3: Terrestrial Ecosystems

79 Subtropical Forest Life Zones of Puerto Rico

83 The Subtropical Dry Forest

94 The Subtropical Moist Forest

105 The Subtropical Wet Forest

113 The Subtropical Rain Forest

125 The Subtropical Lower Montane Wet Forest

132 The Subtropical Lower Montane Rain Forest

135 Agroecosystems

137 Typical Crops of the Tropics
157 Chapter 4: Freshwater Wetlands and Coastal Ecosystems

157 Wetlands Ecosystems

170 Wetlands Regulation

174 Coastal Ecosystems

174 Sandy Beach Habitat 

188 Rocky Shoreline Habitat 

195 Chapter 5: Estuarine Ecosystems

195 Mangrove Forests

200 Ecological Functions of Mangroves

205 Zonation of Mangrove Communities

207 Extent of Puerto Rico’s Mangroves

209 Stressors

212 Values of Mangroves

213 Riverine Estuaries

219 Chapter 6: Marine Ecosystems 

219 Submerged Seagrasses

233 Coral Reefs

248 Keeping Your Keel Off Coral

264 Symbiosis 

267 Coral Dieback 

273 Chapter 7: Disturbances in Puerto Rico and the Caribbean

273 Hurricane Effects on Ecosystems

274 Terrestrial Effects 

278 Marine Effects

282 High Rainfall, Drought, Landslides, and Fire Events

285 The Urban Forest Interface

291 Chapter 8: Environmental Organizations and Environmental 

Infrastructure

291 The El Yunque National Forest and the International Institute of 

Tropical Forestry

298 Puerto Rico’s Commonwealth Forests and Nature Reserves

304 Caribbean Islands National Wildlife Refuge

308 Other Environmental Organizations

310 Acknowledgments 

310 Metric and English Conversion 
311 Literature Cited

322 Further Reading

345 Appendix 1: Common and Scientific Names of Plant and Animal 

Species 

363 Appendix 2: Visiting Puerto Rico

383 Appendix 3: Ecotourism 

387 Appendix 4: Tools

404 Glossary

425 Index
This page is intentionally left blank.
Chapter 1: Overview of Puerto Rico

Introduction

Puerto Rico offers a rich tapestry of environments in which to conduct field studies

in tropical ecology. It has a mountain range oriented east-west with peaks as high

as 1000 meters (4,000 feet). Its boundary on the north is the Atlantic Ocean and to

the south, the Caribbean Sea. The island is bathed by the westerly trade winds,

1

which interact with the sea and mountains to produce an array of rainfall patterns

and orographically induced habitat variation. Some areas in the mountains receive

more than 5000 millimeters (200 inches) of rain annually. Other areas on the

Caribbean rain shadow side receive as little as 254 millimeters (10 inches) in

some years.

In addition, the rainfall produces considerable runoff that results in many

rivers on the island in all directions. The south side has fewer perennial rivers and

is a lower energy coast line, thus affording greater stability to marine ecosystems

such as coral reefs, mangrove swamps, and submerged seagrass beds.

Because of its geographic position, half the year Puerto Rico is also exposed to

major tropical storms. Hurricanes are one of the main ecological disturbances in

Puerto Rico and all adjacent areas of the Caribbean, and have the potential of producing enormous instantaneous and long-term change in all ecosystems, terrestrial

and marine.

Pre-Columbian Puerto Rico had no coconut palms,2 no grapefruit or orange

trees, no coffee groves, no mangoes, no flamboyán or African tulip trees with their

beautiful flowers, and no sugarcane fields. The mangroves that hugged the coasts

were larger and much more widely distributed. The Taíno people that lived on the

island mostly fished and grew corn, yuca, yams, and cotton to supply their needs.

In the 500-plus years since Columbus discovered Puerto Rico (1493, second voyage of discovery), the introduction and growth of nonindigenous European and

African human populations has resulted in enormous habitat alteration throughout

the island. In addition, thousands of alien species of plants and animals have been

introduced, both intentionally and accidentally. Populations of some native species

have undergone dramatic declines, whereas many introduced species have become

naturalized. Destruction of native habitats occurred throughout the island as species

such as sugarcane (Saccharum officinarum L.), tobacco (Nicotiana tabacum L.),

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Guide To The Ecological Systems Of Puerto Rico

1 Bold terms are defined in the glossary.

2 See appendix 1 for Common and Latin names.
citrus (Citrus spp.), coffee (Coffea arabica L.), and bananas (Musa x paradisiaca

L.)—to name just a few—were introduced. Many native habitats and populations

were destroyed without any written description of their presence having been

recorded. Today, large expanses of agricultural lands are “returning to nature” as

much of the sugar plantation land is being abandoned, as sugar is no longer the

dominant crop that it was in the 18th, 19th, and first half of the 20th centuries.

Consequently, Puerto Rico is an interesting case study in that it is an island undergoing significant natural reforestation. Many former agricultural sites will not

return to forest as a result of rapid urban development, growth of tourism centers,

golf courses, light industry, and transportation corridors for the rapidly increasing

use of private automobiles. Human activity has also reduced and, in some cases,

endangered many types of ecosystems, for example, the loss of coral reefs on the

north coast, magnificent lowland forests of the alluvial coastal plains, coastal dune

communities, and the elfin forests on the mountain tops, and the damming of

numerous rivers. 

Puerto Rico is neither a sleepy little Caribbean Island, nor is it a lush tropical

paradise, as is sometimes depicted in tourism advertisements. There are places in

Puerto Rico where both can be found, but, in fact, Puerto Rico today is the commercial engine of the Caribbean, and in many ways it has most of the contemporary problems and concerns that fully developed economies exhibit: air and

water pollution, protection of endangered species and their habitats, forest management, regulation of all forms of waste and their disposal, pesticide regulation,

marine protection, and others. Puerto Rico has over 2 million automobiles, trucks,

and buses constituting one of the highest vehicle densities in the world. At times,

its metropolitan traffic jams rival those of California freeways. It is currently building a 17.2-kilometer (10.3-mile) elevated train/subway at a cost of nearly $2 billion

to alleviate traffic congestion in metropolitan San Juan. Old infrastructure is also 

a big problem for the island’s water supply in that almost 50 percent—about 950 

liters (250 million gallons) per day—of all potable water processed by the Water

Authority is lost prior to delivery because of leaks, broken hydrants, and unmetered

connections to the system. Puerto Rico’s sewerage system is still developing. Fifty

percent of the island lacks sanitary sewer lines, and some communities still have

difficulty meeting secondary sewerage treatment standards, which is of concern to

beach communities and the tourism industry. Sixty-eight treatment plants discharge

into the ocean.

Given Puerto Rico’s many wonderful terrestrial and marine species and 

ecosystems, there is need for a strong conservation ethic and commitment to a

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General Technical Report IITF-35
sustainable future. Many of these species and ecosystems are interrelated and connected in complex ways and are the result of long-term geologic and biologic evolution. As Puerto Rico’s population and associated necessary development increases, the demands and pressures on these ecosystems and species increase

accordingly. Human activity in Puerto Rico is again changing Puerto Rico’s complex landscape, but instead of being largely restricted to agricultural simplification

of the landscape (for which there is an opportunity of recovery), much more

destructive and permanent changes are occurring on the island. These include loss

of large areas to urbanization; serious water pollution associated with improper

disposal of sewage, including hazardous and other solid wastes (industrial and

municipal); overpumping of critically important ground-water supplies; and the

destruction of large numbers of limestone hills, sandy beaches, mangroves, freshwater swamps, and other wetlands. Development in Puerto Rico is growing at a

rate that is surpassing regional carrying capacity in terms of public water supply in

many areas, and at the expense of species and habitats. Puerto Rico is at a critical

crossroads in its environmental history. Many systems are no longer able to perform their functions, and their restoration will be highly unlikely owing to both

cost and complexity. Puerto Rico’s complex environmental issues will need to be

addressed based on needs assessments for future generations. Puerto Rico is heavily subsidized and depends on the importation of huge quantities of food, fossil

fuels, and a vast array of other goods and services (worth $29 billion in 2002).

Sustainability must become the island’s watchword; and all important decisions

must address the three “E’s”: equity, economics, and the environment.

Although Puerto Rico has undergone rapid development in the last five

decades, it still has many special tropical terrestrial and marine habitats and

species, and therefore represents an island with a tremendous mix of opportunities

for pursuing a study of tropical ecosystems. Additionally, there is an excellent published technical information base for the island. Many current studies sponsored by

a variety of federal and commonwealth agencies, universities, and nongovernment

agencies are in progress.

In addition, with growing interest in the tropics, many secondary schools, universities, and teacher training institutes now offer experiential education classes

centered on various aspects of tropical marine and terrestrial ecology. Less formal

experiential education is also available through dozens of ecotourism companies

that specialize in guided trips to the tropics. Tourism in general is now the largest

industry in the world, and ecotourism is the fastest area of growth within this

diverse industry. In 2002, Puerto Rico had 2 million hotel guests. Puerto Rico has

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Guide To The Ecological Systems Of Puerto Rico
seen a substantial increase in ecotourism in the past decade and there is a list of

specialty companies in appendix 3. This field guide is designed as an aid in educating these groups.

This publication was written to help guide a diverse audience—the teacher, 

student, class, or individual reader—in gaining the background needed to understand a select group of tropical ecosystems and species and where to find them

while in Puerto Rico. This is by no means a comprehensive list, but a good representation of the main systems that are relatively easy to access.

A selected series of tropical terrestrial and marine ecosystems has been chosen

for general description, and some of the species typical of those ecosystems will be

highlighted. For more indepth reviews of these species and ecosystems, each section contains references for further reading that provides a broader review of the

more technical literature on the topic.

Puerto Rico—Its History, Politics, and Economy

Early History

No one knows with certainty how long Puerto Rico has been inhabited, but it is 

likely that humans have been present on the island for 2,000 years. The earliest

indigenous population is thought to be from a primitive group called the Siboney

who hunted and gathered. Somewhat later the Igneri established farms and made

pottery. About 700 A.D., the more advanced Taíno were developing population 

centers in many areas of the West Indies. By 1270 A.D., they controlled the island

they called Borikén, which is present day Puerto Rico. As you travel throughout

Puerto Rico today, you will see many references to Borinquen, which is commonly

used as a business name. A form of the word—boricua—is used to designate (with

pride) a person born on the island. The Taínos spread throughout the West Indies,

probably from their origin in mainland Venezuela of South America. When the

Spanish arrived, they called the Taínos the Arawaks. The Taínos were a peaceful

agrarian society that grew corn, yams, and a variety of field crops. They made

bread from yuca, wove cloth from native cotton, and were skilled potters. They

lived in wood frame huts with thatched roofs and played soccer-like ball games on

courts called bateyes (see app. 2, p. 368). It is estimated that approximately 30,000

Taínos inhabited Borinquen in 1493.

By the time Columbus discovered the New World, the Taínos had been under

heavy attack by a very hostile Indian invader, the Caribs. The Caribs burned villages, slaughtered the villagers, took prisoners, and may have practiced cannibalism.

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General Technical Report IITF-35
It is from their tribal name that the word Caribbean was derived. The Caribs had

more advanced technology than the Taínos with which to conduct battles: the bow

and arrow. The Taínos only had spears. When the Spanish came to Puerto Rico, the

Taíno culture went into rapid decline. Not much remains of the Taíno culture.

There are a few words from their language that survive in modern English: barbecue, canoe, hammock, hurricane, and tobacco. In recent years, numerous excavations have been conducted in various places in Puerto Rico, and as a result, we

have a better understanding of their society (fig. 1).

The Isle of Borinquen changed forever on November 18, 1493. It was during

Columbus’s second voyage to the New World that the island was discovered.

Columbus’s 17-vessel fleet anchored on the west coast on November 20. The ships

sent landing parties and took on food and water. They found a Taíno village, but

the people had fled to the mountains. Columbus named this new island San Juan

Bautista (St. John the Baptist), and it was later renamed Puerto Rico (rich port) 

in 1521.

As seen in figure 2, Puerto Rico occupies a strategic point at the entrance to 

the Caribbean. It is the smallest and most eastern of the Greater Antilles and sits

at the top end of the Lesser Antilles, which arc up from South America. Because

of its position, it was of military importance and used as a stopover to and from

Spain (for groups on their way to and from) and other colonization points in the

New World.

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Guide To The Ecological Systems Of Puerto Rico

Figure 1—View of ceremonial areas in the Caguana Indígena Park. 

G. Miller
The earliest Spanish settlers were conquistadores (conquerors), and one of

them aboard the 1493 (second discovery) voyage was Juan Ponce who was from

the province of León in Spain. Juan Ponce, now known as Ponce de León, was

named governor in 1508 and given royal permission to occupy and explore San

Juan Bautista. Initially he searched for gold. In addition to gaining wealth, he was

also interested in converting the indigenous population to Christianity and increasing the glory and wealth of Spain. He and his men landed in a well-protected bay

on the north coast, which he called Puerto Rico. The bay was later renamed San

Juan Bay. The first settlement started by Ponce de León at Caparra proved too distant and unhealthy to be maintained, and so a second settlement was developed on

the island that protected the entrance to the bay. This was the start of present-day

Viejo San Juan (Old San Juan) and it became the capital in 1521. San Juan is the

second oldest city established by Europeans in the New World.

Ponce de León did discover gold and sent tens of thousands of pesos back 

to Spain annually from 1511 to 1520. In a 30-year period (1509–1539), almost

300,000 pesos were sent to Spain. Puerto Rico never achieved the high colonial

status of Cuba, the Dominican Republic, or mainland areas such as Perú or México,

because of its small size, lack of large amounts of precious metals, and relatively

small areas of easily accessed fertile soil for agriculture.

By the 1570s, most mines were closed down, the Taínos were decimated, and

their culture was being assimilated by the dominant European culture through 

intermarriage. 

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General Technical Report IITF-35

Figure 2—Islands of the West Indies and Caribbean Sea.
The Colonial Period

By the mid to late 1500s, it was not certain that the Spanish colonists could support

themselves in Puerto Rico. As the mines failed and no other sources of wealth were

easily accessible, new sources of cashflow had to be established. By this time, the

demand by Europeans for sugar and its various related products was growing. It

was therefore very timely that this lush tropical island, ideal for growing sugarcane,

was in search of a new and sustainable way to pay its bills. There were, however,

big problems associated with sugarcane. The two main problems were that the land

had to be cleared of its native forests, and cane plantations required lots of labor.

Initially, the Taínos were forced into performing these tasks, but they were rapidly

dying out, and later became extinct. However, recent DNA analysis indicates that

many Puerto Ricans have an ancestral link to the Taínos. 

So where would the labor force come from? The conquistadores? No, conquerors rarely performed manual labor. Early in Puerto Rico’s history (1518), 500

African slaves had been brought to Puerto Rico to work in the mines. The need 

for slaves was transferred to the agricultural sector; thus thousands of slaves were

imported, both legally and illegally, beyond the Spanish quotas. As a result of the

increased labor, sugar production grew and mills were constructed in various places

on the island. Later, production of coffee, tobacco, and ginger also became profitable. Puerto Rico now had a land-based economy and landowners, with many

workers. As the mines petered out, San Juan no longer shipped its own gold and

silver, but served as a collection center and safe harbor on the perilous sea routes to

and from Spain. Spain’s treasure fleets were often attacked by pirates, freebooters,

or other nation’s vessels, so Spain decided to fortify San Juan.

In 1539, the construction of El Morro (app. 2), a classic 16th-century fortress,

was initiated. It was not completed for almost 200 years and included moats,

ramps, and tunnels all interlinked with the main fortress with its kitchens, troop

quarters, powder magazines, and dungeons. As a result of the construction of El

Morro and two nearby forts, Puerto Rico became the most fortified colony in the

West Indies. El Morro was attacked many times by various countries, pirates, and

freebooters, but the Spanish flag did not fall until 1898 when the United States 

took over the island by attacking the unfortified south coast.

Puerto Rico remained pretty much a Spanish defensive outpost protecting its

New World colonies and an agrarian society for the next 300 years. As the sugar

industry continued to prosper, by the latter part of the 19th century, Puerto Rico 

the Spanish heritage of the island were being built in Old San Juan. By the time of

the American Revolution, Puerto Rico’s population was nearing 100,000. Large

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Guide To The Ecological Systems Of Puerto Rico
homes reflecting the Spanish heritage of the island were being built in Old San

Juan. They were brick and stucco, with ornate arches, many with interior courtyards and balconies. By 1800, the population had grown to nearly 150,000. Spain

had opened Puerto Rico to greater colonization and in the early 1800s, many

Spanish loyalists sought refuge there from wars for freedom in other Latin

American colonies. By the 1830s, Puerto Rico had a plantation economy with

sugar, coffee, tobacco, and molasses the main exports.

Steps Toward Autonomy

In 1812, Spain elevated Puerto Rico’s status to that of a province, which included

representation in the Spanish Parliament. This status was short-lived, and within 

a couple of years it reverted to colonial status with a series of military governors

appointed by the Spanish Crown. This led to resentment and hostility on the part of

a growing body of Puerto Rican intellectuals. In 1868, an intellectual-led rebellion

occurred in the mountain town of Lares where they proclaimed the free Republic 

of Puerto Rico. The revolt was put down by Spanish troops. Prior to the revolt,

political parties had been outlawed, but shortly after the revolt, the first legal political party was allowed to organize (Liberal Reform Party). Under its influence, the

Spanish government outlawed slavery in Puerto Rico in 1873. At that time only 

5 percent of the population was African. Puerto Rico, since its colonial period, 

was pretty much culturally and racially homogenous. The Liberal Reform Party

changed its name to the Autonomist Party in 1887 in order to seek autonomy rather

than absolute independence from Spain. Autonomy was achieved in 1897 under the

leadership of Luis Muñoz Rivera. Once again, Puerto Rico could elect voting delegates to the Spanish Parliament. The newly granted autonomy also permitted the

election of Puerto Rico’s first legislature in March 1898.

The American Period

These reforms and newly won freedoms were abruptly ended. In April 1898, the 

Spanish-American War started as a result of the blowing up of the U.S.S. Maine, a

battleship at anchor in the harbor of Havana, Cuba. The war was very short, and by

August 13, it was over in Puerto Rico. An American military force of 16,000 landed on the south coast at Guánica and marched overland to San Juan, but the war

ended before they crossed the Cordillera Central Mountains. On October 18, the

Spanish flag was lowered over the governor’s residence at La Fortaleza. Under

agreements signed at the Treaty of Paris, Puerto Rico was officially ceded to the

United States on December 19, 1898. 

8

General Technical Report IITF-35
At the start of the 20th century, Puerto Rico had a population of nearly 1 million that was mostly poor, agrarian, and illiterate with little or no opportunity for

education. Most of the island’s land was in the hands of a few wealthy families and

absentee owners. Coffee was the dominant export product, but it waned owing to

new tariffs imposed by the United States and catastrophic hurricane damage. 

Almost overnight Puerto Rico’s newly won opportunities for self-rule were

gone and all local political power was turned over to the U.S. military government.

It abolished the newly formed parliament, local governments were reorganized, 

and new judicial and tax systems were put in place based on American forms of

government.

Many Puerto Ricans identified with American principles of democracy and the 

hard-won freedoms brought about by the U.S. revolution. They were hopeful that

the United States would willingly grant Puerto Rico many new political freedoms.

This did not occur. Instead, the U.S. Congress passed the Foraker Act (Organic

Act) in 1900. It was more restrictive than the freedoms Puerto Rico had won under

the autonomy agreements with Spain. Under U.S. rule, the governor would be

appointed by the President, as were all other major office holders, including the

justices of the Puerto Rico Supreme Court. Local laws passed by the newly established Puerto Rico House of Delegates were subject to veto by U.S. Congress.

Puerto Rico could only send a nonvoting resident commissioner to Congress. The

Foraker Act also prohibited Puerto Rico from negotiating trade treaties with foreign

nations and retired the Puerto Rican peso at 60 cents to the dollar. This caused a

breach in international trade relations and a 40-percent rise in the cost of living. It

also caused the price of land to fall and allowed the big wealthy U.S. sugar corporations to come to Puerto Rico and acquire vast areas of land, even though no corporation was allowed to own over 202 hectares (500 acres). This then prompted the

rapid rise of sugar as the main exportable crop. Because of the foreign trade restrictions, by 1930 more than 90 percent of the island’s sugar trade was with the United

States and resulted in a monoculture economy for Puerto Rico. The big four U.S.

sugar companies were able to show huge profits (22.5 percent return on capital) in

the 1920s and 1930s. Much of the profit was due to the extremely low wages paid

by the companies to the Puerto Rican workers (63 cents for a 10-hour day in 1917).

The Foraker Act was restrictive politically and economically, but did provide

for new and expanded economic activities such as free trade with the United States.

It also exempted Puerto Rico and its inhabitants from U.S. taxes. Federal excise

taxes on rum and tobacco produced in Puerto Rico were returned to the island’s

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Guide To The Ecological Systems Of Puerto Rico
treasury. Although the Foraker Act was economically good for Puerto Rico, it was

despised politically and thus resulted in continued local interest in Puerto Rican

independence. This undercurrent, coupled with World War I, caused the United

States to review Puerto Rico’s status resulting in the Jones Act in 1917. This act

granted collective naturalized citizenship to all Puerto Ricans on a voluntary basis.

There were 1.2 million Puerto Rico residents at the time and all but 288 accepted

citizenship. The Jones Act also allowed Puerto Ricans to enter the United States

without travel restrictions, and established a Puerto Rico Bill of Rights, which created a new two-house legislature. Popular elections would decide a 19-member

Senate and a 37-member House of Representatives. The Jones Act also required

Puerto Ricans to serve in the U.S. military, and 18,000 Puerto Ricans served in

World War I. After the war, more attempts at autonomy were proposed but were

rejected by the U.S. Congress.

Free trade with the United States greatly enhanced sugar trade, and by the

1920s, 75 percent of the employed people in Puerto Rico were involved in the

sugar industry controlled by U.S. corporations. When the world’s economy collapsed in the late 1920s, the period of the Great Depression was particularly hard

on Puerto Rico. By the 1930s, Puerto Rico’s population had grown to 1.5 million,

and the effects of the depression increased unemployment, which made living conditions worse. Per capita net income dropped from $122 in 1930, to $85 in 1933.

The U.S. Congress had its hands full at home and basically ignored the plight of

Puerto Rico. As a result, for the first time, hostility and resentment fueled a strong

independence movement in the 1930s; however, it was not strong enough to defeat

the other pro-statehood parties. In 1936, a new political party and leader emerged

who was to dominate Puerto Rican politics for three decades. Luis Muñoz Marín

founded the Popular Democratic Party (PDP) or Populares. In combination with an

enlightened New Deal Governor, Rexford Tugwell, who was appointed by

President Roosevelt, they began to reorganize the economic and social structure of

Puerto Rico. Unfortunately, the 202 hectares (500-acre) land provision of the

Organic Act was never enforced, and by the end of the 1930s, 51 corporations

owned more than 100 000 hectares (250,000 acres), much of it not used for food

production. This forced Puerto Rico to import (by design) vast quantities of food

from the United States at high prices because of U.S. tariffs. The result was to turn

farmers into virtual serfs. One of Muñoz Marín’s great initiatives was to press

Governor Tugwell to help in the passage of a Land Reform Act. This was finally

accomplished in 1941 after the U.S. Supreme Court in 1940 said that Puerto Rico

had the right to enforce its land reform laws and limit land ownership to 202

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General Technical Report IITF-35
hectares (500 acres) or less. True land reform was the result, with many rura

l residents now able to buy 10-hectare (25-acre) parcels. This allowed them to 

grow crops for profit for both export and internal use, thereby breaking up the land

monopoly of the large sugar companies. Many see this as the seminal event instrumental in the real socioeconomic gains that would come in the late 1940s with the

advent of Operation Bootstrap, a massive effort to raise the standard of living for

the island’s inhabitants and make the island more self-sufficient. Little attention

was paid to gaining Puerto Rico’s independence for 10 years, and out of frustration,

a schism occurred in the PDP and the modern Puerto Rican Independence Party

(PIP) formed in 1946.

Upon Roosevelt’s death, Harry Truman appointed a new governor, Jesús T.

Piñero, the first Puerto Rican to be named to the post. This created better relations

with the United States. The U.S.-Puerto Rico relations were also strengthened as a

result of the 65,000 Puerto Ricans who served in World War II. In 1947, Congress

amended the Jones Act allowing all future governors to be popularly elected and

with power to appoint Puerto Rico Supreme Court Justices. In 1948, the first popularly elected governor was Luis Muñoz Marín. 

From 1948 to 1960, Puerto Rico and the U.S. government formulated and

implemented Operation Bootstrap. The result was 450 new factories and businesses

being started and the beginning of a major transition for Puerto Rico from a largely

rural agrarian society, to the modern industrial economy it is today. By 1956, industrial development had surpassed agriculture as the principal source of income. New

initiatives in public education and vocational training were part of this program.

There was a second phase in Operation Bootstrap in the 1970s that was stimulated

by Fomento, Puerto Rico’s Development Bank and Economic Development

Administration. This program attracted capital-intensive industries such as petrochemical and pharmaceutical companies. The Operation Bootstrap Program also

made it possible to develop a thriving professional class of lawyers, engineers,

business managers, and financial executives needed to make these businesses run.

It worked, and Puerto Rico became a showcase for other less developed economies

in the Caribbean to emulate.

In 1950, following Governor Muñoz Marín’s request, the U.S. Congress declared Puerto Rico a Free Associated State (Estado Libre Asociado), or Commonwealth. As a commonwealth, all existing ties to the United States would remain,

but Puerto Rico could now write its own constitution. In the watershed election of

1952, the PDP won 67 percent of the vote, PIP 19 percent, and the pro-Statehood

Republican Party (SRP) 13 percent. By 1964, when Muñoz Marín retired from the

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Guide To The Ecological Systems Of Puerto Rico
governorship, the SRP had grown to 36 percent of the vote, and the PIP had slipped

to 3 percent. In 1967, there was a plebiscite over Puerto Rico’s political status with

the options being commonwealth, statehood, or full independence. In that instance,

independence was soundly defeated, with statehood coming in second (39 percent)

to the island’s current commonwealth status (60 percent). Congress in 1979 passed

a resolution supporting Puerto Rico’s right to self-determination. Under new leadership the pro-statehood party was renamed Partido Nuevo Progresista (PNP) and,

to date, has elected three governors. However, even with a PNP governor, in the

last political status vote of 1998 the commonwealth received 49 percent, statehood

46 percent, and independence 4 percent. Once again in 1998, Puerto Ricans demonstrated their preference for the status quo. In November 2000, Puerto Rico elected

the first female governor, Sila María Calderón, who ran as an anti-statehood candidate for the PDP. The current governor of Puerto Rico, Aníbal Acevedo Vilá, is

from the PDP party.

Puerto Rico elects a new legislature and governor every 4 years. Governors can

serve a maximum of two consecutive terms. The Governor appoints a cabinet consisting of his or her department heads. The bicameral legislature is made up of two

houses; the House of Representatives has 54 members and the Senate 28. Both

houses are popularly elected. The government operates on a model similar to that

of the United States, and Puerto Rico is set up like 1 of the 50 states. The island

has 78 political districts (municipalities; fig. 3) and each has its own local political

machine and locally elected officials such as city mayors and town councils.

Puerto Rico now participates in U.S. presidential primaries and sends delegates

to the national political conventions, but it still does not have any voting representation in U.S. Congress, nor do Puerto Ricans vote for the President unless they

reside in one of the 50 states. Puerto Rico cannot enter into treaties, issue money 

or passports, maintain armed forces, or exchange diplomats with foreign countries.

They still do not pay any federal taxes, but as it turns out, commonwealth taxes are

usually as high as U.S. taxes. Should Puerto Rico strongly indicate by vote and formal request its desire to become the 51st state, all that Congress would have to do

is pass an enabling act by simple majority of both houses and have it signed by the

President. There are three standards for statehood consideration: (1) that the new

citizens abide by the American form of government, (2) that the majority of the

commonwealth’s electorate wants statehood, and (3) that they be able to meet their

state and federal obligations.

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13

Guide To The Ecological Systems Of Puerto Rico

Figure 3—Municipalities of Puerto Rico.
Contemporary Puerto Rico

Population—

According to the 2000 U.S. census, the island of Puerto Rico has a population of

slightly over 3.8 million compared to 3.15 million in 1990. There are also another

3.4 million Puerto Ricans residing in the United States, largely in metropolitan

areas such as New York, Philadelphia, Chicago, and Orlando. More Puerto Ricans

now live in Florida than in the capital of San Juan. These mainland residents are 

an outgrowth of a migratory shift in the Puerto Rican population that began in the

1950s and 1960s largely as a result of rapid population growth and poor economic

opportunities on the island. Migration had an “Alice in Wonderland” effect, that is,

the economy had to run very fast just to stand still because, during that period,

Puerto Rico’s birthrate was 35 per 1,000, while its death rate had dropped to only 

7 per 1,000, so the population was growing rapidly. This migration trend was still

occurring in the 1990s when on average 6,500 people per year left the island.

Although Puerto Rico’s population is still growing, its rate of increase is declining

and may not be sufficient to replace itself (0.6 percent/year) in the long term.

The island’s population is primarily urban (72 percent), with greater San Juan

having a metropolitan population in excess of 1 million. The remaining 28 percent

is spread throughout the rural areas except for restricted commonwealth or federal

lands. Puerto Rico has one of the highest population densities in the world, in

excess of 450 per square kilometer (1,100 people per square mile). Population density in metropolitan San Juan is about 4000 per square kilometer (10,000 per square

mile). Life expectancy is slightly lower than in the United States at 80 years for

females and 71 years for males. Infant mortality is somewhat higher than in the

United States with 13.4 deaths per 1,000 live births.

Puerto Rico has a growing elderly population; people 60 years or older account

for over 15 percent of the population. Those under 19 years account for about 33

percent of the population. According to the 2000 census, over 80 percent is white, 

8 percent is black, and approximately 12 percent are members of other ethnic

groups.

Puerto Rico is Spanish in atmosphere and culture. The island’s population is

99.9 percent Hispanic and the first language is Spanish, with English as its second

language. Most Puerto Ricans know some English, as it is a compulsory subject in

the school system. Many older people use it sparingly, and school dropouts often

do not attain fluency; thus English fluency is estimated to be less than 50 percent.

The island’s government is officially bilingual. The language and culture issues 

are quite contentious, as most Puerto Ricans do not want to give up their Spanish 

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General Technical Report IITF-35
heritage. Many still identify closely with Spain and Spanish-speaking South and

Central American countries and do not want to give up Spanish as their official 

language. Historically, the religion of the island’s people has been mostly Roman

Catholic. Many non-Catholic denominations actively came to Puerto Rico looking

for converts, especially the Adventists and Mormons. Today the people are 40 percent Roman Catholic, 40 percent Protestant, and 20 percent other religions. Puerto

Rico is also North American in status and progress because of its unique commonwealth status with the United States. High standards of health, food preparation,

water treatment, education, and the presence of organizations such as the Rotary

Club, the Masons, the Lions Club, the Elks, and the Boy Scouts and Girl Scouts 

of America all provide a North American flavor to the island.

Puerto Rico has a 90 percent literacy rate. There are over 600,000 public school

students, making it the third largest school district in the United States. Education

is compulsory from ages 5 to 21. About 42 percent of Puerto Rican young people

graduate from high school and many pursue advanced education. The University of

Puerto Rico was founded in 1903 as a U.S. land grant institution (fig. 4). Its main

campus in Río Piedras is a fully comprehensive Ph.D.-granting, teaching/research

liberal arts university, with a law and medical school. Its land grant counterpart at

Mayagüez offers a full array of degrees, and houses the engineering, agriculture,

and marine sciences programs. The university also has a designated liberal arts

campus at Cayey and eight other campuses. Total enrollment today is more than

71,000. The university’s combined budget is more than $1 billion per year. There

are 30 campuses of higher learning in Puerto Rico, and they graduate nearly 45,000

students per year.

Economics—

Puerto Rico is still very economically dependent on the United States. The U.S.

presence affects Puerto Ricans’ economic lives every day, from the U.S. currency

in their pockets, to the many products sold on their store shelves. The U.S. government subsidizes Puerto Rico with about $15.48 billion in federal assistance payments yearly, which covers everything from education to food stamps. It is estimated that in 1999, federal subsidies for unemployment compensation and housing for

a family of four cost the U.S. government over $19,000 per year. Should Puerto

Rico become the 51st state, it would be eligible for another $3.5 billion in federal

assistance (estimated). Approximately 40 percent of Puerto Rico’s economy has

been based on special tax exemption legislation that allows U.S. manufacturers to

avoid paying federal tax on profits made in Puerto Rico. This is estimated to be in

excess of $4 billion per year. The U.S. industries benefit from operations in Puerto

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Guide To The Ecological Systems Of Puerto Rico
Rico and generate billions of dollars in annual revenue. Puerto Ricans also benefit

from the federal guarantee on bank savings, and from the millions of dollars

received in disaster relief after a hurricane. Per capita income for the island is

$7,600 a year, which is half that of the poorest state, Mississippi, but considerably

higher than its nearest Greater Antilles neighbor, the Dominican Republic, where

average per capita income is only $1,600 per year. More than 37 percent of households earn less than $10,000 per year. Official unemployment fluctuates between

11 and 20 percent, although there is considerable employment in various activities

not included in the official statistics. Actual unemployment is probably higher, and

may in fact be close to 20 percent. In 2000, 1.15 million people were employed.

Nearly 60 percent of the population falls within the U.S. government’s poverty definition, and over 30 percent of the population receives some form of public assistance. This includes some 425,000 families (1.1 million people) who received an

average of $220 a month in the nutritional assistance program. It is estimated that

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General Technical Report IITF-35

Figure 4—View of the main campus of the University of Puerto Rico, Río Piedras with the

bell tower and royal palms lining the entrance. 

G. Miller
as much as 50 percent of this money ($650 million) goes to purchase nonfood

items. According to the 2000 census, approximately 73 percent of homes are 

family-owned, and 64 percent of families own one or two automobiles.

The U.S./Puerto Rico association is also beneficial to the United States. The

U.S. economy benefits on the order of $720 billion as a result of commerce with

the island and the many U.S. companies located in Puerto Rico. Puerto Rico must

use the U.S. Merchant Marine to transfer its products and cannot engage in international commercial activity without the consent of the United States. The United

States has used Puerto Rico as a strategic military base since the turn of the 20th

century, and it remained the U.S. Navy’s primary training facility for amphibious

warfare and carrier-based tactical bombing practice until 2003.

As cited earlier, numerous U.S. manufacturers have built manufacturing plants

in Puerto Rico and account for 42 percent of the gross domestic product (GDP)

employing about 24 percent of the workforce (160,000). Industry is the main

source of income for Puerto Rico. The services sector accounts for 37 percent of

GDP and employs 291,000 people. Various government agencies produce 11 percent of GDP and have 245,000 employees. The utilities sector also produces 11

percent of GDP, with 32,000 employees. Agriculture today accounts for only 1 

percent of GDP and employs 26,000. Construction employs 85,000 people. Puerto

Rico now has 70 pharmaceutical firms whose products are viewed as recessionproof. Puerto Rico exports more than $25 billion in products ranging from medicine, refined petroleum products, scientific equipment and machinery, to rum,

clothing, and shoes. Unfortunately, the island’s high-value mineral resource base 

is quite limited. It has a large population on a small land base, and island food production is now low. This results in the need for islanders to spend billions on food

imports. In spite of this, Puerto Ricans enjoy the highest standard of living and per

capita income in Latin America.

In August 1996, the U.S. government began the phasing out of federal tax benefits that had positioned Puerto Rico as the preferred site for stateside manufacturers. This resulted from the fact that not enough new jobs were being created for the

large amounts of tax writeoffs the multinational corporations were receiving. This

came at a time when the federal government was also trimming budgets and eligibility for social welfare program spending and preferential treatment for Puerto

Rican products. As a result, from 1996 to 2000, Puerto Rico lost 16,500 manufacturing jobs. By early 2002, the total had risen to 27,000 jobs lost. In light of these

changes, Puerto Rico’s government is developing a new economic development

program called the “New Economic Model,” which has tax incentives, increased

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Guide To The Ecological Systems Of Puerto Rico
foreign trade and investment, and greater-self reliance as major themes that will

lead Puerto Rico’s economy into the new millennium. The Puerto Rico government

is also trying to convince Washington to amend Section 956 of the federal tax code,

which again would provide favored tax status for controlled foreign corporations

operating in U.S. territories. This would permit up to 90 percent of their earnings 

to be returned to the United States without taxation. There is also discussion about

trying to have Puerto Rico included in the Earned Income Tax Credit system of the

U.S. tax code, as it would subsidize minimum-wage employees, bringing wages up

to $14,000 or $15,000 per year.

Another aspect of Puerto Rico’s economy, of which little is known, is the 

informal, unregulated, and illegal underground economy. This is mostly a cash and

service economy. The illegal trade of drugs, for example, has an estimated gross

cashflow of $20 billion per year according to the Drug Enforcement Agency. An

estimated 20 percent of all cocaine imported into the U.S. enters via Puerto Rico

and the U.S. Virgin Islands. Four billion dollars remain in Puerto Rico and surface

in the economy. For example, the largest Puerto Rican bank (Banco Popular) was

fined $21 million for not reporting hundreds of millions of dollars in questionable

cash transactions in one of its banks in Old San Juan. Some Puerto Ricans take the

view that it does not pay to work in the official economy and that they are better

off getting welfare payments, food coupons, and taking part in the underground

economy. The underground economy may be as high as one third (or more) of the

total island economy. All of which is untaxed and unregulated.

For more information on Puerto Rico’s history, see Aliotta 1994, Cockburn

2003, Dietz 1986, Fernández 1996, Golding 1973, Haslip-Viera 2001, Lewis 1963,

López 1981, Morris 1995, Rouse 1993, U.S. Department of Commerce 2001, and

U.S. Department of the Interior 1996.

Physical and Climatic Zones of Puerto Rico

Geography

Puerto Rico is the smallest of the Greater Antilles chain, which also includes Cuba, 

Jamaica, and Hispaniola (Haiti and the Dominican Republic). Puerto Rico is 145

kilometers (90 miles) from the Dominican Republic to the west and 67 kilometers

(40 miles) from the U.S. Virgin Islands to the east. It is 1665 kilometers (1,000

miles) southeast of Miami and 2840 kilometers (1,700 miles) south of New York

City. On the north and east side is the Atlantic Ocean, and on the south and west is

the Caribbean Sea. It is positioned at the north end of a group of lesser islands that

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General Technical Report IITF-35
form an arc running down to Venezuela 847 kilometers (525 miles) to the south.

They are called the Lesser Antilles and include the U.S. and British Virgin Islands,

French Guadeloupe, Martinique, and numerous other islands down to Grenada,

Barbados, and Trinidad. All totaled, in the Greater and Lesser Antilles, there are

approximately 7,000 islands that make up what are called the West Indies (fig. 2).

The land area of Puerto Rico and adjacent islands is 8897 square kilometers

(3,435 square miles). It is 56 kilometers (35 miles) north to south, 176 kilometers

(110 miles) east to west, and is rectangular in shape. Puerto Rico is somewhat

smaller than the state of Connecticut. Its coastline is 500 kilometers (311 miles)

with numerous harbors and beaches. Its land cover is variable, with much of the

center of the island consumed by high mountains (40 percent), surrounded by

foothills (35 percent), and a narrow coastal plain (25 percent). Virtually all of the

coastal plain is in intensive agriculture, roads, or under urbanization. In a recent

study by Helmer et al. (2002), they found that 41.6 percent of the island is now

covered by closed forest, 36.7 percent is in pasture and grassland, 5.9 percent is in

agriculture, 2.4 percent is in coffee plantations, 10.5 percent is urban/developed,

and 3.9 percent is in various other categories including mines, rock/sand areas, salt

and mudflats, emergent wetlands, and water bodies. Approximately 5 percent of

Puerto Rico’s forest area is under protection.

There are a variety of ecosystems distributed laterally and vertically according

to topography, altitude, soils, rainfall, and a variety of other factors. The island

lies directly in the path of the trade winds that blow from the Atlantic Ocean to the

east. This assures a fairly reliable source of rain and occasionally a hurricane or

two. The presence of high mountains creates a very interesting rainfall pattern

resulting in the creation of an orographic rain shadow on the Caribbean side of

the central mountain ranges, and some rain shadow valleys in the interior sections

of the mountains.

The highest altitude on the island is 1338 meters (4,389 feet) in the Cordillera

Central range at Cerro de Punta, and there are numerous peaks over 915 meters

(3,000 feet). Cerro de Punta is just north of Ponce within the Toro Negro

Commonwealth Forest and can be accessed by Route 143 (Luis Muñoz Marín

Panoramic Highway). Mountains can be seen from anywhere on the island. The

entire center of the island is a continuous series of mountains that basically cuts the

island in half as they run east to west from Humacao to Mayagüez. Approximately

25 percent of the island is above 305 meters (1,000 feet) altitude. The high mountains exhibit high degrees of slope to the south and east, and the north slopes are

heavily eroded with numerous river valleys. The south slopes tend to be dry much

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Guide To The Ecological Systems Of Puerto Rico
of the year owing to the orographic rain shadow. During tropical storms and hurricanes, rivers on the south coast may become rapid torrents that flood extensive

areas and often kill domestic grazing animals or human squatters living in the dry

riverbeds or flood plains. The Cordillera Central has a break in the area of Caguas,

and the mountain range located northeast is the Sierra de Luquillo. This range also

has a series of peaks in excess of 915 meters (3,000 feet), and these peaks experience the highest amounts of rainfall on the island. The Luquillo range includes the

El Yunque National Forest, also designated as the Luquillo Experimental Forest

and known as the world-famous Luquillo Rain Forest or El Yunque. This 11 200-

hectare (28,000-acre) forest is a biosphere reserve site and attracts about three 

quarters of a million visitors per year.

The soils of the coastal plain are conducive to agriculture, and much of it was

cleared in the 17th and 18th centuries for sugarcane. Adjacent to the coast, the land

is fairly level and has been converted to agriculture, urban development, and transportation corridors. Periodically, there are rocky promontories and karst foothills

such as those near Arecibo, Fajardo, Cabo Rojo, and Guánica. Sand dune areas and

beaches such as at Isabela, Piñones, Luquillo, and Boquerón dot the coastline.

Climate

Puerto Rico is in that large area north and south of the equator called the tropics 

(25° N and S). Its maritime climate is very pleasant because it is bathed by warm

sea breezes throughout the year. This prevents major fluctuations in temperature.

Rainfall is distributed throughout the year, with May through November considered

the rainy period. January to March is a bit dryer, but may have cold fronts coming

in from the temperate zone to the north that can produce 1 to 2 days of rain.

Extremes in temperature are rare, with high temperatures rarely going into the mid

30s °C (90 °F) except on the south coast and lows rarely below 25 °C (60 °F) in

the mountains. Smallest daily temperature fluctuations occur in the coastal plain 

5 to 8 °C (10 to 15 °F), whereas the mountains experience the largest daily fluctuations 8 to 12 °C (15 to 20 °F). There is not much variation seasonally like there is

in the temperate zone, in fact there is greater night to day temperature variation

than there is seasonally. However, there is considerable variation in temperature

and precipitation resulting from variable topography and prevailing winds. The

east-west mountain chain intercepts the easterly trade winds; thus it provides the

north side with an abundance of rain. The Cordillera Central and Luquillo ranges

cause the warm moisture-laden air masses to cool and lose much of their moisture

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General Technical Report IITF-35
as they pass over the north and eastern sides. As they pass over the mountains, the

amount of rain decreases resulting in the south coast being much dryer (fig. 5). 

Areas in the Luquillo Rain Forest often receive more than 5000 millimeters

(200 inches) of rain, whereas areas in the Guánica Forest 42 kilometers (50 miles)

away may only receive 900 millimeters (36 inches). The capital city of San Juan

annually receives 1700 millimeters (68 inches) of rain on the north coast, whereas

the second largest city, Ponce on the south coast, receives only 950 millimeters 

(38 inches). Some areas on the south coast may receive only 254 millimeters (10

inches) in dry years. The island’s average rainfall is 1800 millimeters (71 inches)

per year.

The mountainous topography produces temperature variation. In general, for

every 300-meter (1,000-foot) increase in altitude, temperature decreases 2 to 3 °C

(3 to 4 °F). On average, San Juan’s coastal temperature will be 4 °C (7 °F) warmer

than a town in the mountains such as Barranquitas. Many mountain communities

experience almost idyllic climate, with temperature regimes that require neither air

conditioning nor heating. People in the warmer, more humid coastal areas may use

air conditioning throughout the year. Puerto Rico does not experience freezing temperatures, even in the highest mountains where temperatures rarely fall below 

18 °C (65 °F). Much of the island experiences high humidity year round.

Many streams are formed as a result of the mountainous terrain. There are 

hundreds of mapped streams on the island, 50 of these are classed as rivers. Most

rivers on the north side are larger in volume and length. Six major rivers originate

in the Luquillo chain. Most of the rivers are dammed and used for regional or community water supplies, irrigation, and power production. The majority of the reservoirs have problems with sedimentation, water quality, and introduced exotic

aquatic plants such as Eichornia crassipes (Mart.) Solms (water hyacinth) and

Pistia stratiotes L. (water lettuce).

Hurricanes

The island is in the hurricane belt of the western Atlantic and Caribbean. Most hurricanes form as tropical lows off the coast of Africa from June through October and

intensify as they proceed west over the warm waters of the Atlantic. Hurricanes are

Puerto Rico’s number one weather problem because of the catastrophic high winds

and waves, large volumes of rain, and the enormous structural change they can 

produce on natural ecosystems, and on human populations and their infrastructure.

Most hurricanes are peripheral and produce minor effects, but those termed killer

hurricanes owing to their intensity and direct hits, have the potential to produce

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Guide To The Ecological Systems Of Puerto Rico
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General Technical Report IITF-35

Figure 5—Annual mean precipitation for Puerto Rico.
enormous damage and hardship. Typically, 6 to 10 hurricanes develop yearly in the

western North Atlantic region. Hurricanes have impacted Puerto Rico recently, with

Hortense, Hugo, and George classed as major hurricanes. A separate section on

hurricanes and other disturbances follows, and hurricane effects are discussed in

the sections on forest zones and coral reefs.

Geology

Geologically, Puerto Rico is complex. Its origin is volcanic, and it initially arose 

as a result of seismic activity associated with the Caribbean-North American plate

boundary zone. The initial formation was believed to have been 140 to 200 million

years ago in the Triassic era. These volcanic deposits were then folded, faulted, and

uplifted to produce the Cordillera Central Mountains province (fig. 6). Puerto Rico

is relatively young, only about 100 million years old. Evidence of its volcanic period can be seen in weathered pillow lavas observable in road cuts south of Cayey on

Route 52. Secondary metamorphic and igneous activities resulted in gneisses and

serpentinite formations. Large outcrops of serpentinite occur on the western end 

of the Cordillera Central in the Maricao district west to Mayagüez (app. 2). This is

a beautiful blue-green rock that produces a soil typically low in calcium and high 

in chromium or other metals. Some plants in western Puerto Rico show hyperaccumulations of nickel (Brooks 1987).

Younger sedimentary rocks and sediments are present throughout the coastal

plain province. The carbonate province is located on the flanks of the central

mountain core and is composed of marl, dolomite, and calcareous sandstones. On

the north coast there is a spectacular display of karst topography that ranges back

to 30 million years. A large area of limestone is located along the south coast and

underlays the Guánica subtropical dry forest. In the karst district that runs from

Loíza to just east of Aguadilla, many haystack-shaped hills dot the landscape by 

the thousands. They are locally called mogotes or haystack hills.

The rivers that run north from the Cordillera Central in the karst area produce

deep cuts in the landscape owing to differential rates of erosion in the limestone.

Some of the rivers periodically run underground in association with caves. There

are thousands of caves and sinkholes in the region (see app. 2). A more detailed

description of karst will be presented in the forest zone section.

Puerto Rico’s geological formations have yielded very few mineable mineral

resources. In the early 1500s, gold was mined, but gold was basically gone by the

1570s. Some commercial gypsum, dolomite, and phosphate have been mined (app.

2). Today, extensive areas of aggregate and road metal are being consumed. Most

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Guide To The Ecological Systems Of Puerto Rico
houses today are constructed from cement. Large quantities of beach sand are

mined, but at great expense to commercial grade beaches and resulting in areas of

extensive coastal erosion such as at Isabela on the north coast. The most productive

aspects of mining are nonmetals such as clays, marble, stone, sand, gravel, limestone, and salt. There are deposits of nickel and copper on the island. There is a

large deposit of low-grade copper in the Cordillera Central near Lares. It has not

been mined owing to cost, low metal concentration, and environmental concerns.

There are peat deposits on the north coast, but probably not extensive enough for

commercial mining. Roughly 10,000 workers are employed in mineral-related

industries concentrated in the San Juan and Ponce areas. Puerto Rico has no coal,

oil, or natural gas deposits. Fossil fuels, mainly oil, supply 90 percent of its power,

and they must be imported. About 10 percent of its power is derived from dammed

rivers. Many homes and businesses use passive solar heating for hot water.

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Figure 6—Geology of Puerto Rico.
Soils

Soil is the product of the weathering of rocks. When water runs across or through 

parent geologic strata, erosion and leaching occurs. Various other physical, chemical, and biological conditions of the environment further aid in the weakening and

disintegration of these strata promoting the accumulation of released particles in

the formation of soil. Many conditions are responsible for the characteristics exhibited by each soil type such as composition of the original substrate, slope, temperature, aspect, rainfall, acid rain, biological activities, and gaseous content to name a

few. These conditions lead to the specific colors, structure, and nutrient availability

of each soil. Because of its complex geology and climate, Puerto Rico shows a

variety of soils, with 9 of the 11 possible soil orders present. The most extensive

soil group is the Inceptisols, which cover 37 percent of the island. Inceptisols are

found on steep slopes of 20 to 60 percent in eastern Puerto Rico. Many of these

soils are eroded owing to cultivation on steep slopes. Inceptisols are typical of

mountainous areas, are only slightly weathered, and their horizons are still developing. Landslides frequently occur on these soils.

Ultisols cover nearly 27 percent of the landscape and are found in uplands 

of the western sections of the Cordillera Central. These are typical of humid environments, usually nutrient poor, and mostly found on ancient strata or highly

weathered alluvial sites. Mollisols constitute 21 percent of the island’s soils and 

are found over limestone in the rain shadow foothills on the south side of the

Cordillera Central, on limestone sediments on the north coast, and in various flood

plains and alluvial fans in river systems. They have a dark, thick A-horizon; are

soft and crumbly; and are high in organic matter. Six other soil orders cover the

remaining 15 percent of the landscape (fig. 7).

Puerto Rico has 29 suborders and 164 classified soil series. About 28 percent

of the island has soils suitable for agriculture. Much of this was historically used

for sugarcane production. Today, some of the best soils are disappearing in areas

undergoing rapid urbanization. This is critical because Puerto Rico is heavily

dependent on food imports and the loss of the best agricultural soils only increases

that dependence. For additional descriptions of the soils of the Caribbean and

Puerto Rico, see the recent review by Lugo et al. 2000.

The physical features just described have a direct effect on the distribution of

plant species and communities. Plant communities are distributed over the landscape based on elevation, soils, geology, rainfall, temperatures, aspect, and numerous interactions among other plants and animals; the distribution of communities

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Guide To The Ecological Systems Of Puerto Rico
that results spatially are referred to as plant geography or phytogeography. Later

in this document is a description of the major forest types of Puerto Rico that will

relate to these factors. However, for now, note that the major forest type distributions are related closely to parent materials as seen in table 1.

For more information on the physical and climatic zones of Puerto Rico, see

Beinroth 1969, 1971; Birdsey and Weaver 1982; Bush et al. 1995; Calvesbert 1970;

Giusti 1980; Lugo-López and Rivera 1977; Malfait and Dinkelman 1972; Monroe

1980; Picó 1974; and Weaver 1992. 

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General Technical Report IITF-35

Figure 7—General soils of Puerto Rico.

Table 1—Forest type and distribution of parent material

Forest type based on climate

Parent material Dry forest Moist forest Wet forest Rain forest

Alluvial X X

Limestone X X X

Ultramaphic X X X

Volcanic X X X
Chapter 2: Flora and Fauna of Puerto

Rico and the Caribbean

General Review of the Flora

Puerto Rico has a diverse native flora. More than 180 higher vascular plant 

families and 3,100 species are present. The vast majority are native species. Up to

300 species are naturalized aliens. There are more than 250 endemics. Currently,

there are no known families or genera endemic to Puerto Rico. The flora is composed of 143 dicot families, 33 monocot families, and five families of gymnosperms. In addition, there are 15 families of lower vascular plants, including

members of the Psilotaceae (wiskfern), Selaginellaceae (spikemosses), Isoetaceae

(quillworts), and various fern families. Much of the plant diversity relates to the

island’s diverse set of habitats, which range from dry rocky coastlines, to very wet

montane elfin forests. The presence of a high central mountain corridor with deep

valleys, highly variable rainfall patterns, orographic rain shadows, and a variety of

soil types all lend themselves to supporting a complex flora. In addition, an estimated 3,000 alien species have been introduced from various areas of the New and

Old World tropics; thus, there are well over 200 plant families in Puerto Rico and

the adjacent islands.

Puerto Rico’s native flora has a high affinity with the flora of the Greater

Antilles to the west (Hispaniola, Cuba, and Jamaica). It also has much in common

with the flora of the Lesser Antilles and South America. Many of the plants are

found throughout the Caribbean, such as the sandy beach plants, weedy grasses,

legumes, asters, and lawn weeds such as the common plantain. A small number of

plants also have an affinity with Florida and the Gulf Coast region of North

America, some of which may have arrived via Neotropical migratory birds (feathers, feet, digestive tract vectoring). A few species probably rode the currents and

the hurricane-force winds from Africa.

Of the alien species, probably 1,000 were introduced because of their beauty,

such as Spathodea campanulata Beauv. (African tulip tree) (box 1).1 Another 1,000

were probably brought because they afforded food, clothing, shelter, construction,

or medicinal possibilities. For example, Persea americana Mill. (avocado) seeds do

not float and are too large to be vectored by birds. It was probably brought to the

island by indigenous people.

27

Guide To The Ecological Systems Of Puerto Rico

1 See appendix 1 for Common and Latin Names.
28

General Technical Report IITF-35

Box 1. Spathodea campanulata Beauv. (African tulip tree) 

It seems that no matter where you are in Puerto Rico, if you look out into 

the distance, you are likely to see a tree that looks like a red fountain. If you

examine the flowers you will see brilliant orange-red petals much like the

shape and color of tulips. Its origin is west central equatorial Africa, thus the

name “African tulip tree.” It belongs to the family Bignoniaceae, known

worldwide for its large colorful flowers. It is a fast-growing tree, as are many

introduced aliens, but its wood is light and has little commercial value. Owing

to its beautiful flowers appearing from October to April (some plants bloom

year round), it is widely planted in many tropical areas as an ornamental. In

Puerto Rico, it has become naturalized and is the most common tree in the

island’s secondary forests (see graph). It is not a forest dominant and usually

fades as the stand matures because it is shade intolerant. Recently, almost pure

stands of Spathodea campanulata have been found in Puerto Rico and are currently under investigation. 

Its leaves are pinnately compound and oppositely arranged and may be

over 30 centimeters (1 foot) long. They can grow in fairly dry areas where

average moisture is about 1000 millimeters (40 inches), but grow best where

mean annual precipitation is 1600 millimeters (64 inches) or more. When

growing in dryer climates, they may become deciduous. Many people use

them as shade trees in their yards where they can achieve heights in excess 

Relative species importance by basal area in Puerto Rico timberland in 1960.
29

Guide To The Ecological Systems Of Puerto Rico

Box 1. continued

30 meters (100 feet) in 30 to 40 

years. Older trees may develop a

flared trunk base, referred to as buttressing. The largest tree of this

species is in the city of Arecibo and

exhibits a height of 35 meters (115

feet), a crown diameter of 15 meters

(49 feet) and a circumference of 5.49

meters (18 feet).

African tulip trees are fairly 

resistant to infection, but their 

branches are subject to wind 

damage because of their light 

wood. This may lead to secondary 

heart-wood rot, which makes the tree susceptible to snapping during severe

storms. As with many successional species, their life expectancy is short. They

produce large volumes of small wind-dispersed seeds, thus they can be carried

long distances. They are invaders of open sunny landscapes where they grow

rapidly and help stabilize the soil.

In Africa the seeds have some

food and folk medicine value.

Although its wood has only lowgrade commercial value, this plant 

is one of the true beauties of the

Puerto Rican forest, and its true 

value is the pleasure it brings to 

people as its showy flowers light 

up the landscape.

For more details on the African

tulip tree, see Francis 1990, Little 

and Wadsworth 1964, and Franco 

et al. 1997.

Leaves, flowers, and fruit of the African tulip

tree.

African tulip trees are found all throughout

Puerto Rico commen.
Most of Puerto Rico’s endemic species are associated with the mountain

province. Mountains, with their variable growth conditions and deep valleys, can

foster genetic variation and isolation that may lead to ecotypic variation, and over

time, evolution of a new species. A higher percentage of endemics are found in the

mountains than in the coastal province. The lowland species are more cosmopolitan

in their distribution throughout much of the Caribbean. Puerto Rico is third in number and fourth in percentage of endemics in the Greater Antilles (table 2). Cuba has

the highest number. On the other hand, Puerto Rico has the highest density of

species, whereas Cuba is fourth. Liogier and Martorell (2000) indicated that the

smaller the island, the higher the species density, and the larger the island, the higher the percentage of endemism.

Myrtaceae (myrtles) is the family with highest endemism in Puerto Rico (31

species), Asteraceae (asters) has 19 endemics present, and the Polypodiaceae

(ferns) 16 species. Puerto Rico has only two endemic palms, whereas Cuba has 60

palm species that are endemic.

The Caribbean region is floristically rich. According to Lugo et al. (2000), the

region harbors an estimated 12,000 to 15,000 vascular plant species, one endemic

family, 200 endemic genera in 49 families, and 7,500 endemic species. The regional flora is highly endemic or Caribbean in distribution, rather than of mainland

affinity. The flora exhibits numerous species per unit area as evidenced by speciesarea curves that exhibit steep slopes. It appears that species extinction in the region

has been minimal. Again, according to Lugo et al. (2000), it appears that the forces

that shaped Caribbean vegetation may have also provided resilience to the flora

that would prove of benefit during the onslaught of human activity.

The three biggest plant families in the world are the Asteraceae (asters),

Orchidaceae (orchids), and Fabaceae (legumes). Orchids and legumes are much

more common in the tropics than the asters. Puerto Rico’s four largest angiosperm

30

General Technical Report IITF-35

Table 2—Floristic analysis of the Greater Antilles

Number of Density of 

Island Area speciesa speciesb Endemism

km2 Percent

Puerto Rico 8 897 3,126 0.350 8

Jamaica 10 991 2,888 .262 27

Hispaniola 77 914 5,000 .064 36

Cuba 114 524 6,000 .052 49 a Number of species includes native and naturalized.

b Density of species is total species divided by square kilometer.

Source: Modified from Liogier and Martorell 2000.
families are the Poaceae (grasses), Fabaceae (legumes), Orchidaceae (orchids), and

the Asteraceae (asters). The largest family is the Polypodiaceae, which is one of the

fern families. It has 287 species present. Twenty-eight ferns are limited to calcareous areas, five to serpentine, and five to salty habitats. Puerto Rico’s largest plant

families are presented in table 3.

Puerto Rico’s flora has 37 plant families that are monogeneric and monospecific (table 4). Two families are monocots, 32 are dicot families, and 3 are lower

vascular plant families.

In table 5 you will find a representative group of tropical plant families with

some of their interesting genera and species that many people not from the tropics

may be able to recognize because of products that are derived from them. Some

31

Guide To The Ecological Systems Of Puerto Rico

Table 3—Puerto Rico’s largest plant families

Plant group Family Species present

Monocots Poaceae 257

Orchidaceae 144

Cyperaceae 135

Dicots Fabaceae 244

Asteraceae 140

Euphorbiaceae 109

Rubiaceae 107

Myrtaceaea 77

Ferns Polypodiaceae 287

a Family with largest number of endemics.

Table 4—Partial list of plant families found in Puerto Rico with only one

genus and one species

Plant group Family Plant names

Monocots Ruppiaceae Ruppia maritima L. (widgeon grass)

Dicots Avicenniaceae Avicennia germinans L. (black mangrove)

Bataceae Batis maritima L. (saltwort)

Bixaceae Bixa orellana L. (lipstick tree)

Cannabaceae Cannabis sativa L. (marijuana)

Caricaceae Carica papaya L. (papaya)

Ceratophyllaceae Ceratophyllum demersum L. (coontail)

Cyrillaceae Cyrilla racemiflora L. (palo colorado)

Droseraceae Drosera capillaris Poir. (sundew)

Juglandaceae Juglans jaimaicensis C. DC. (Jamaican walnut)

Myristicaceae Myristica fragrans Houtt. (nutmeg)

Lower plants Psilotaceae Psilotum nudum (L.) Beauv. (wiskfern)

Azollaceae Azolla caroliniana Wild. (water fern)

Osmundaceae Osmunda cinnamomea L. (cinnamon fern)
32

General Technical Report IITF-35

Table 5—Representative list of tropical plant families

Family Species Common name/notes

Agavaceae Agave L. spp. Century plant–tequila and rope sisal

Anacardiaceae Mangifera indica L. Mango–fruits

Annonaceae Annona reticulata L. Custard apple–tropical fruit

Apocynaceae Plumeria rubra L. and Frangipani–perfume and floral arrangements

P. alba L.

Araceae Monstera spp. Philodendron group–epiphytes–2,000 species 

worldwide, 92 percent tropical–houseplants

Bixaceae Bixa orellana L. Lipstick tree, food coloring

Bombacaceae Ceiba pentandra (L.) Gaertn. Kapok–life vests and pillows

Bromeliaceae Ananas comosus (L.) Merrill; Air or well plants–epiphytes

Guzmania spp. Piña or pineapple

Cactaceae Opuntia spp. Succulent desert and dry coastal forest plants

Caricaceae Carica papaya L. Papaya fruit

Clusiaceae Clusia rosea Jacq. Autograph tree, strangler epiphyte

Fabaceae (Leguminosae) Delonix regia (Bojer) Raf.; Flamboyán and sensitive plants–legumes are 

Mimosa pudica L. very important nitrogen fixers in the soil, 

attractive flowers

Flacourticeae Banara vanderbiltii Urban. Palo de ramón–rarest tree in Puerto Rico 

Lecythidaceae Couroupita guianensis Aubl. Cannonball tree–cauliflory

Liliaceae Sansevieria spp.; Aloe vera Snake plant; mother-in-law’s tongue– 

houseplants and lotions

Malvaceae Hibiscus rosa-sinensis L. Red hibiscus shrub.

Moraceae Artocarpus altilis Breadfruit; 

(Parkinson) Fosberg

Musaceae Musa spp. Bananas and plantains

Nyctaginaceae Bougainvillea spectabilis Willd. Brilliant flowering shrub–many colors

Orchidaceae Vanilla planifolia G. Jackson Vanilla for food additive; 20,000 species of 

orchid worldwide, second largest family 

of plants in the world

Palmaceae Roystonea regia (H.B.K.) Royal palm and coconut palm–the beautiful 

O.F. Cook- (royal palm); palms of the tropics

Cocos nucifera L.

Pandanaceae Pandanus odoratissimus Screw pine, large prop roots

Piperaceae Piper spp. Pepper family

Poaceae (Gramineae) Saccharum officinarum L.; Sugarcane; bambo

Bambusa vulgaris Schrad 

ex. Wendl.

Polygonaceae Coccoloba uvifera Sea grapes

Rhizophoraceae and Rhizophora mangle L. Red mangroves

Avicenniaceae Avicennia germinans L. Black mangroves 

Vivipary, specialized prop and pneumatophore roots

Rubiaceae Coffea arabica L. Coffee

Sapotaceae Manilkara zapota (L.) V. Royen Gum tree–Chicklets chewing gum

Sterculiaceae Theobroma cacao L. Chocolate tree

Strelitziaceae Strelitzia reginae Banks ex Dryand Bird-of-paradise

Zingiberaceae Alpinia purpurata (Veill.) Schum. Ginger for foods
people may have them as houseplants, or they may eat or drink them with some

regularity.

For more information on the flora of Puerto Rico, visit the University of Puerto

Rico, Botanical Gardens (app. 2) and see Liogier 1997, Liogier and Martorell 2000,

Little and Wadsworth 1964, Little et al. 1974, and Proctor 1989.

Trees

Today, forests cover approximately 40 percent of Puerto Rico. At one point, more 

than 90 percent of the forests of the island had been cleared, and those forested

areas that remained were heavily disturbed. Since the 1960s, forest cover has been

steadily increasing owing to industrialization and urbanization. Many formerly

cleared areas that were on steep slopes or that became unproductive owing to poor

agricultural practices are undergoing natural reforestation. The island is greener

today than at any time in the 20th century.

Over the past 60 years, the landscapes of the island have been transformed

from agricultural to a mixture of urban and rural landscapes. The long-term trend 

in land use is for Puerto Rico to become an urban island. This transformation—

powered by economic and social changes—has also transformed the ecosystems of

the island. The forests of today are not the same as those of yesterday, and they will

certainly be different in the future. For example, more than 200 species of trees

have been introduced by humans and some are now naturalized and enrich the new

forests of Puerto Rico. Spathodea campanulata Beauv. (African tulip tree), an alien

species, is now the most common tree in the new landscape, a landscape dominated

by humans. This new landscape has more species than the landscapes of the past,

resulting from the introduction of alien species, a low rate of extinctions, and the

creation of new habitats by people.

Most trees in Puerto Rico are tropical evergreen hardwoods, unlike fastgrowing evergreen pine forests of the Southeastern United States. Many are slow

growers, with high wood density and good commercial value such as Manilkara

bidentata (A. DC.) Chev. (ausubo)—for use in cathedral and house beams—or

have high specific gravity (>1) such as Guaiacum officinale L. (lignum vitae).

Those species that grow fast have light woods like Ochroma pyramidale (Cav.)

Urban (balsa), Cecropia schreberiana Miq. (trumpet tree), and Bursera simaruba

(L.) Sarg. (Gumbo limbo).

Although there has been massive disturbance of forest habitat throughout the

island, there has been no recorded extinction of tree species. Little et al. (1974)

indicated that the island has 547 native tree species (table 6). Today, Puerto Rico

33

Guide To The Ecological Systems Of Puerto Rico
has an additional 120 species of naturalized alien tree species. Naturalized species

are those that are growing and reproducing in the landscape and that appear “natural,” even though there is an historical estimate of their approximate date of introduction. The total number of tree species in Puerto Rico is 667 when naturalized

species are considered. Numerous other introduced trees are present (83 species on

the island), but are not considered naturalized. Thus, the total number of trees rises

to 750 when the alien species are included. This number is surprisingly higher than

the total number of tree species found in the lower 48 continental United States

(679 species). Most of the alien trees were introduced for utilitarian reasons such as

ornamentals, food, drink, wood, and agricultural testing. More than 75 trees native

to Puerto Rico are found in the Southern United States (Florida and adjacent Gulf

States).

Table 7, modified from Trees of Puerto Rico and the Virgin Islands (second

volume; Little et al. 1974) tabulates important families with large numbers of

species. Thirteen plant families contain 387 tree species, which is more than 50

percent of the total. All of these families contain 15 or more species.

Because Puerto Rico developed as a submarine volcanic island from the ocean

floor, it was never attached to a continent. As a result, all species present, both

plant and animal, had to migrate great distances over open ocean or were of recent

human introduction. An analysis of tree species’ ranges and centers of distribution

(table 8) illustrates the geographic affinities and important areas of origin of the

woody flora of Puerto Rico.

The largest source of species appears to be from the Neotropical continental

mainland. In addition, speciation was involved in migration of species via the

Antillean chain of islands. It appears that endemism was important in the Puerto

Rican flora whereby an original immigrant diverged genetically owing to physical

and climatic isolation. Today, 21 percent of the trees in Puerto Rico and adjacent

34

General Technical Report IITF-35

Table 6—Taxonomic groupings of Puerto Rico’s trees

Number

Native species 547

Introduced species 203

Total 750

Native genera 272

Introduced genera 104

Total 376

Native families 85

Introduced families 14

Total 99

Source: Little et al. 1974.
islands are found nowhere else. This figure is higher than that cited for the entire

vascular flora, which is 8 percent. Of the total 232 plant species endemic to Puerto

Rico, 61 percent are trees (Figueroa Colón 1996).

Isolated oceanic islands are often areas that express high endemism. Little

(1970) cited 61 trees endemic to Puerto Rico, with 25 species found only in the

Luquillo Mountains. This number was expanded to 115 in the second volume of

Trees of Puerto Rico and the Virgin Islands (Little et al. 1974). Of these, 29

endemics are considered rare or endangered and worthy of protection. Fortunately,

most of these species benefit from de facto protection, as they are found in the 

public forests of Puerto Rico. Nineteen are not present in protected areas, but are

found on private lands. The rarest tree in Puerto Rico is Banara vanderbiltii Urban

35

Guide To The Ecological Systems Of Puerto Rico

Table 7—Important families with many tree species in Puerto Rico 

Family Total species Native Introduced

Fabaceae 70 29 41

Myrtaceae 54 45 9

Rubiaceae 48 42 6

Euphorbiaceae 36 27 9

Melastomataceae 35 34 1

Rutaceae 23 13 10

Sapotaceae 22 20 2

Moraceae 20 9 11

Lauraceae 17 13 4

Bignoniaceae 17 9 8

Solanaceae 15 13 2

Flacourtiaceae 15 12 3

Palmaceae 15 10 5

Source: Little et al. 1974.

Table 8—Probable origin of Puerto Rico’s trees 

Origin Percent

Continental 41.9

South and Central America 22.1

South America only 10.1

Central America only 9.7

West Indies 32.4

Greater and Lesser Antilles 14.6

Greater Antilles only 14.1

Lesser Antilles only 3.7

Endemic to Puerto Rico 21.0

Puerto Rico only 19.9

Puerto Rico and adjacent islands 1.1

Source: Little et al. 1974.
(Flacourtiaceae). There are only two known individuals found near the city of

Bayamón. The highest degree of endemism is found in the mountain province, with

the Luquillo Experimental Forest having 48 percent of all endemic trees in Puerto

Rico. Most endemics are not widespread. Forty-seven percent of all Puerto Rico

endemics are known to occur in three locations or fewer (Figueroa Colón 1996).

The dry forest at Guánica has 16 endemics.

Alien species of plants and animals are of great concern throughout the world

because of their potential competition with native species. A naturalized species is

an alien that has been able to adapt to the new habitat and is able to successfully

reproduce. Swietenia mahagoni (L.) Jacq. (West Indian mahogany) is now successfully reproducing in the dry zone forest of Puerto Rico. Other species are able to

grow as successional species, that is, fast growing in well-lighted conditions.

Spathodea campanulata is doing this throughout much of the island, especially in

successional pasture lands and roadsides. Other aliens are naturalizing at the sites

of human introduction such as parks, yards, and businesses. Delonix regia (Bojer)

Raf. (flamboyán tree) with its brilliant red blooms and prolific seed production is

very successful in these situations. Most species in this category of alien naturalization are rarely studied unless they become a pest. Then a plant-related agency 

is consulted to see what can be done. By then it may be too late and elimination

impossible. Other alien trees invade pastures and reduce herbaceous productivity

including Albizia procera (Roxb.) Benth (white albizia) and Acacia farnesiana (L.)

Willd. (sweet acacia).

Boxes 2 to 6 are profiles of six woody plants likely to be seen throughout

Puerto Rico. Some are native and others introduced. A couple cause dermatitis.

For review of the growth, reproduction, and ecology of tropical trees see Vozzo

(2002), and for further reading see Birdsey and Weaver 1982; Chinea-Rivera 1990;

Francis 1990, 1998; Francis and Alemañy 1996; Francis and Liogier 1991; Franco

et al. 1997; Hargreaves and Hargreaves 1965; Little and Wadsworth 1964; Schubert

1979; and Wadsworth 1997. 

General Review of the Fauna 

Puerto Rico has a diverse fauna. Animals present on the island represent 30 of 

the 34 phyla and 72 of 84 classes of animals. There are over 275 orders present 

that contain 1,500 of 6,200 animal families. Three of the animal families present

are endemic to the Antilles. At least 10,335 species have been identified for the

36

General Technical Report IITF-35

Continued on page 42.
37

Guide To The Ecological Systems Of Puerto Rico

Box 2. Comocladia dodonaea (L.) Urban (poison chicharrón) 

Puerto Rico has three plant species that 

are members of the Anacardiaceae

(cashew family), which produce skin

reactions in humans like those produced

by Rhus radicans L. (poison ivy, also a

member of the cashew family) in the

United States. One of Puerto Rico’s

species is not as widespread as the 

others, so Metopium toxiferum (L.) 

Kang & Urban (Florida poison tree) 

will only be mentioned here. It is a small

evergreen tree with alternate, pinnately

compound leaves, with three to seven 

leaflets, orange fruits (drupe), and which 

produces a poisonous sap. It is present in the Guánica area on the south coast.

It is very abundant on Mona Island off the west coast.

Two other shrubs/small trees that can produce serious cases of dermatitis

belong to the genus Comocladia and are much more common. Fortunately,

none of the species are as common as is poison ivy in the United States.

Comocladia dodonaea occurs mostly as a shrub (< 4.5 meters [15 feet],

but on occasion it will be treelike in size (> 4.5 meters [15 feet]. It is easily

recognized because of its prominent, spiny, odd, pinnately compound leaves.

The plant does not produce an obvious crown; instead clusters of evergreen,

alternately arranged leaves form around the ends of a few branches. The pinnately compound leaves range from 7.5 to 17.5 centimeters (3 to 7 inches) in

length and may have 11 to 21 ovate leaflets that are sessile and appear curved.

The leaflets are usually tinged red-orange and possess three to five sharp

spines. It produces a nondescript panicle inflorescence with many small red

flowers that produce a red fleshy fruit (drupe). Flowering is typically from

December to March and fruiting, April to July. This species is very common in

open areas of the dry southwestern coast, and in forest thickets throughout the

dryer sections of the coastal plain and adjacent foothills up to 304 meters

(1,000 feet) elevation. It is also common in the dryer upper elevation of

haystack hills in the north coast karst region. 

This species has no economic value other than its effects on humans

because of its potentially serious skin irritation. All parts of the plant should be

avoided.

Leaves, twigs, flower, and fruit of

Commocladia dodonea (L.) Urban.
38

General Technical Report IITF-35

Box 3. Comocladia glabra L. (J.A. Shultes) Spreng. (Poison carrasco)

Comocladia glabra L. (J.A. Shultes) 

Spreng. also grows both as a shrub or

small tree up to 6 meters (20 feet).

Occasionally it will also produce a vinelike habit. It grows as a slender understory species and is unusual in that it

tends to grow unbranched with a terminal cluster of large odd pinnately 

compound leaves. The leaves are alternately arranged, can be 30.5 to 61 centimeters (1 to 2 feet) long, and can have

11 to 31 lance-shaped leaflets. The

leaflets can be 5 to 17.5 centimeters (2 

to 7 inches) long. Each main leaf vein

extends through the margin in the form 

of a prominent spine. Both male and female flowers are on the same plant,

with very small red petals densely crowded on a panicle-like inflorescence.

The fruits are red-black fleshy drupes. Flowering and fruiting are intermittent

throughout the year. Its bark is light gray and rough. This species is common

in moist forest types of Puerto Rico up to 304 meters (1,000 feet) altitude. It 

is found in the lower elevations of the karst region on the north coast. This

species is absent from the dry habitats of the southwest and from elevations

over 304 meters (1,000 feet) in the mountains.

Like C. dodonaea it has no economic value. All parts of the plant should

be avoided, especially its milky sap. 

For more information on poisonous woody plants in Puerto Rico, see Little

et al. 1974.

Leaves, twigs, flower, and fruit of

Commocladia glabra (J.A. Shultes).
39

Guide To The Ecological Systems Of Puerto Rico

Box 4. Ceiba pentandra (L.) Gaertn. (kapok) (Known locally, as Ceiba)

As you travel around Puerto Rico, 

be sure to be on the lookout for large

trees with big flared trunks called buttresses, and light gray bark and spines

when young. On occasion you may 

see them preserved in highway 

medians such as on Route 2 west of

Arecibo or in a special park developed

to honor the largest tree in Ponce. This

species can achieve great size and is

probably one of the tree world’s best

examples of plank buttressing. These

buttresses appear as flat triangular

woody growths that form in the angle 

between the base of the trunk and a 

lateral root running radially at the surface of the soil. The “plank-like” buttress

is secondary growth that develops from the upper side of the root. The buttress

operates much like an engineered bridge buttress whereby the great weight of

the tree is spread by the flared base. The root systems of kapok (also called

ceiba or silk cotton tree) lack a well-defined tap root and consist of laterals

with very shallow sinker roots. Size and number of buttresses differ with the

mass and spread of the crown. Some buttresses can grow in excess of 6 meters

(20 feet) in height and length (see photo below). The size and length of the

roots and buttresses can crack roads, walls, and foundations. The adaptive

value of buttress growth to the tree is the increased resistance to blowdown

owing to storms or gravity. They also reduce stem rocking in storms, which

would heavily damage the fine roots necessary for absorption. In windy areas,

kapoks have a tendency to develop buttresses predominantly on the windward

side. They grow well in both dry and wet areas and will be found from the

coastal plain to the mountains in Puerto Rico.

Ceibas are native to South America and one of the largest trees in the

Neotropics. They were probably introduced to Puerto Rico in prehistory. They

require great amounts of light and are typical of open habitats, such as abandoned farm land and deforested slopes. Their leaves are palmately compound,

with 5 to 8 leaflets. They normally flower December to February after they

The leaf, stem, and flower structure of Ceiba

pentandra (l.) Gaertn. (Kapok).
40

General Technical Report IITF-35

Box 4. continued

reach 5 years of age. The flowers are whitepink and clustered at ends of branches. Inside

the fruit pods (capsules), the seeds produced 

by kapok have long silky hairs, thus the name

“silk cotton tree.” This silk aids in wind dispersal. The silk is called kapok and has good

commercial value. It is used as filler in life

vests, pillows, mattresses, and as a cloth fiber.

This tree is a plantation species. The 

kapok fiber makes it more valuable than its 

wood and will produce silk for half a century. 

The wood is good for paper production and 

a variety of low-end products like packaging 

or fuel. The plank buttresses can be used for 

table tops. In some cultures, kapok trees are sacred and various parts of the

plant are used in herbal medicines. The seeds contain oil used as a lubricant

and in soaps and paint. Its leaves can be used for animal fodder. Indigenous

peoples carved sea-going canoes out of the kapok tree’s main stem. One such

canoe was reported to carry 150 passengers and was used to meet Columbus on

his second voyage.

The largest kapok tree in Puerto Rico is in the village of Villalba. It is 38.7

meters (127 feet) tall, with a crown spread of 44.5 meters (146 feet) and a 

circumference of 19.8 meters (65 feet). Many cities in the tropics have kapok

trees planted in the center of their town’s plaza.

In Ponce on the south coast, there is a small public park dedicated to the

protection of a giant 400-year-old Ceiba pentandra within the city limits. It 

is located just past the intersection of Routes 133 and 14 at the edge of the

Portugués River. For years, groups wanted to cut it down to expand a bus park

and an adjacent street. Each time, citizens fought for it until it received its current protected status. Unfortunately, storms over the years have greatly reduced

its crown, and its buttresses have been severely cut back to accommodate city

growth. In the 1970s, this tree was much larger than it is today, especially its

buttresses.

For additional information on kapok, see Chinea-Rivera 1990 and Little

and Wadsworth 1964.

Typical buttress development of

Ceiba pentandra (L.) (kapok).

G. Miller
41

Guide To The Ecological Systems Of Puerto Rico

Box 5. Delonix regia (Bojer) Raf. (flamboyant) (Locally known as

flamboyán)

By most accounts this may be the most 

beautiful tree in the tropics (see photo). 

It is native to Madagascar, where it is 

an endangered species. It has been 

widely introduced throughout the tropical world, including Puerto Rico. It is

often used as backdrop in commercial

photography such as the production 

of postcards, calendars, and tourist

brochures because of its brilliant 

orange-red flowers.

Flamboyán is a medium-sized tree

with a broad umbrella-like crown that

can achieve a height of 15 meters (50 

feet). Their broad crowns often produce 

a tunnel effect when they are grown close together along roads. It is a deciduous species during the dry season. It produces even, twice pinnately compound leaves that are alternately arranged. The leaves are 20 to 50 centimeters

(8 to 20 inches) long with numerous subdivisions bearing up to 40 pairs of

very small, oblong sessile leaflets.

The persistent red-orange flowers cover the entire crown and are produced

in profusion from May through August. Flowers are produced in racemes at

the ends of branches. Each flower is 15 to 25 centimeters (6 to 10 inches)

across and is composed of five unequally-sized petals, one of which has white

streaks. The fruits are long, hard, black legumes (like string beans), which

grow to 50 centimeters (20 inches) in length and contain many bean-like

seeds. The pendulous legumes are persistent throughout much of the year 

and very evident when the trees are leafless.

Older trees will likely exhibit buttressed trunks, with gray-brown smooth

bark and large lenticels. Long horizontal branches produce a crown that may

be wider than the tree is tall. The tree’s wood is heavy, coarse-grained, weak,

and brittle, thus it is of low commercial wood value. It is easily broken during

storms. The wood and the large machete-shaped fruits are often used for fuel. 

The leaf, flower, and fruit structures of

Delonix regia (Bojer) Ref.
island2 Table 9 provides an approximate number of species found in the principal

animal groups.

According to Vélez, about 50 percent of Puerto Rico’s animals are terrestrial

(more than 5,100 species), marine species comprise 38 percent of the fauna

(approximately 3,900 species), freshwater species make up nearly 8 percent (almost

800 species), and symbiotic species comprise 5 percent of the fauna (over 500

species).

Puerto Rico has no large terrestrial charismatic animal species and probably

never did. Those animals that might be considered charismatic are the Puerto Rican

parrot (Amazona vittata), the Antillean manatee (Trichechus manatus) and the

42

General Technical Report IITF-35

Box 5. continued

The largest flamboyán is located in Utuado. It is 32 meters (104 feet) tall, has 

a crown spread of 25 meters (83 feet), and has a circumference of 2.7 meters

(8.8 feet).

Flamboyán is a widely planted tree throughout the island as a horticultural

species around homes, in plazas, and along streets and highways for its shade

and flowers. It grows well in both dry and moist areas of the island. It does

best in full sunlight and in areas with a short dry period. It is common to see

large brown termite mounds located on the trunk or axils of main branches.

For more information about this species, see Little and Wadsworth 1964

and Schubert 1979.

Closeup of flowers of Delonix regia found all over Puerto Rico.

2 Lecture delivered at the University of Puerto Rico by M. Vélez in 2001 on the taxonomic 

families and species represented in Puerto Rico.
43

Guide To The Ecological Systems Of Puerto Rico

Box 6. Clusia rosea Jacq. (postcard tree) (Locally called Cupey)

Clusia rosea is an unusual tree species 

because it can start out as an epiphyte 

and may become a strangler as it develops.

It is also unusual in that its thick leathery

leaves can be written upon, thus the common name postcard or autograph tree. In

fact, early conquistadores are known to

have made playing cards from the leaves,

scratching figures and numbers on their

surfaces.

The tree has a broad dense evergreen 

crown and may grow to heights of 18 

meters (60 feet). The leaves are oppositely 

arranged, very thick, deep green, and with 

a shiny top surface. The leathery leaves are obovate in shape, the margins are

turned under, and the apex is rounded or notched. It produces large showy

white-pink flowers composed of 6 to 8 petals at the ends of branches. The

species is dioecious (separate male and female trees). The yellow-brown fruits

are capsules with 7 to 9 chambers that produce numerous yellow sticky seeds

that are eaten and vectored by bats and birds. They are poisonous to humans.

Cupey trees flower and fruit throughout the year. Its bark is gray, smooth to

warty, with a pink inner bark; when cut it will exude a yellow latex.

In the wild, cupey often begins life as an epiphyte (air plant), much like

figs, with its seeds germinating in the canopy and sending long aerial roots to

the ground. The roots gradually coalesce and eventually encircle the structural

host tree. The trunk of Clusia encases the host, which may die a few years

later. A more complete description of epiphytes is included in the forest zones

section. Very often at the base of the tree, prop roots will be present as the

original root system does not start as a primary root. Prop roots may also grow

from the main branches, producing the visual effect often associated with

banyan trees. The largest cupey is located in San Juan and is 20.4 meters (67

feet) tall, has a crown spread of 24.4 meters (80 feet), and is 98 centimeters

(39 inches) in circumference.

Cupey is native to Puerto Rico and most of the West Indies. It is frequently

propagated by seed harvest or cuttings. It has a variety of low economic uses

The leaf, flower, and fruit structures of

Clusia rosa Jacq. (Postcard tree).
Coquí (Eleutherodactylus coqui) tree frog. Large native mammal species were 

historically extremely rare in Puerto Rico. Animals typical of Neotropical mainland

lowland forests such as tapirs, jaguars, coatis, and monkeys were never found in

Puerto Rico. The lack of large mammals can be accounted for because of the

island’s physical isolation, that is, no natural land bridge afforded migration from

North or Central America and its physical location so far east in the Antillean

44

General Technical Report IITF-35

Box 6. continued

including use of the fruits in dry floral arrangements and use of the wood for

cheap furniture, fuel, fence posts, and rural construction. Its latex can be harvested and used to caulk wood structures or fill cracks. Cupey can grow in a

variety of habitats, from the highest mountains to the beach. The tree is most

typically found in shallow, rocky, moist soils. It is salt-spray resistant, thus 

can be used as a species to retain sand near beaches and as a seaside ornamental. It is common to riverine habitats and is most common in the moist forest

karst areas of northern Puerto Rico, where it grows vine-like on cliff faces of

the haystack hills and in sinkholes. Cupey is often considered a pest species

because of its ability to strangle and kill more valuable trees, but this appears

uncommon. Very often termites will build mounds in their branches. It is frequently damaged by hurricanes because it does not defoliate easily and thus its

foliage acts like a sail, which causes the tree to topple or suffer crown damage.

For more information about this species, see Francis 1993, Little and

Wadsworth 1979, and Schubert 1979.

Table 9—Number of species present in the principal animal phyla of Puerto 

Ricoa

Species 

Phylum Animal groups present

Porifera Sponges 151

Cnidaria Hydra, jellyfish, anemones, corals 202

Platyhelminthes Flatworms 226

Nematoda Roundworms 250

Annelida Segmented worms 262

Arthropoda Insects, spiders, crustaceans 5,377

Mollusca Snails, clams, squids, octopus, chitons 1,359

Echinodermata Sea stars, sea urchins, sea cucumbers 110

Chordata Tunicates, birds, reptiles, amphibians, fish, mammals 1,427

a Approximately 9,364 species are found in the nine largest phyla listed.
chain. Physically, these animals could not swim the distances involved, and 

likewise, large mammals are absent in all of the easterly Lesser Antillean islands.

Since discovery in 1493, animal extinctions have been recorded throughout the

Caribbean islands. Waide (1987) cited 11 recent bird extinctions for the Caribbean,

with two of those from Puerto Rico. There are currently a number of species on 

the U.S. and Puerto Rico threatened and endangered species list (see the section

on endangered species that follows). According to the natural history record of

Puerto Rico, there were ground sloths and large rodents called hutías on the island.

There were also native rats, moles, shrews, and hedgehogs in the fossil record. All

were apparently extinct by the beginning of colonization. All native terrestrial

mammals are now extinct except for bats. Also, large populations of reptiles are

reduced, with the rock iguana now confined to offshore islands. It is assumed that

human disturbance activities associated with habitat destruction, the introduction of

alien species, and possibly hunting pressures accounted for most of the problems

encountered by the native fauna in the West Indies (see Puerto Rican parrot section

that follows). According to Brooks and Smith (2001), species extinctions resulting

from human pressures have struck the West Indies on a large scale. Of the 197

endemic mammals and birds found across the islands, at least 43 have become

extinct over the last 500 years, three orders of magnitude higher than expected

given species lifetimes in the fossil record. Worse yet, 84 more Caribbean endemic

mammals and birds are classified on the Red List as threatened, with a high probability of extinction in the medium-term future.

Marine animal biodiversity is also declining in the Caribbean region. The

native manatees, monk seals, and crocodiles once present, are largely extinct

throughout most of their natural ranges. In addition, the populations of the large 

sea turtles (Green [Chelonia mydas], Hawksbill [Eretmochelys imbricata], and

Leatherback [Dermochelys coriacea]) are all depressed and are all listed as endangered species throughout their ranges in the United States and Puerto Rico, as are

all species of sea turtles. 

At the time of Spain’s ceding of Puerto Rico to the United States, little was

known about Puerto Rico’s animal life, but in 1916 a major expedition was organized to study all aspects of Puerto Rico’s natural history by the New York Academy

of Science. For a review of the history of various zoological studies conducted in

Puerto Rico, see Wadsworth (1970) and Figueroa Colón (1996). The New York

Academy expedition resulted in a long list of publications describing most of the

main animal groups in the Annals of the New York Academy of Science through the

1940s. An updated 80-year reassessment of the island’s natural history was recently

published (Figueroa Colón 1996).

45

Guide To The Ecological Systems Of Puerto Rico
In terms of past and recent studies, the insect fauna, as would be expected, has

the largest group of identified species. There are 5,066 species catalogued from 

25 insect orders (Capriles 1996). The insect fauna of Puerto Rico is much better

known than that of any other Antillean island. Although Puerto Rico has been

explored and extensively studied for its insects, it appears that insect diversity

should be twice as large as it is, compared to other West Indian land areas (Capriles

1996). Martorell (1945) explained the low species diversity on the basis of geography. It appears likely that Puerto Rico’s geography, in terms of its eastern position

in the Greater Antilles and northern position of the Lesser Antilles, restricts access

to new insects. The trade winds that come from the open Atlantic in the east or

northeast, where there are few land masses, do not promote the distribution of

insects to Puerto Rico. However, hurricanes transport insects from Africa to Puerto

Rico and the Caribbean. The heavy destruction of forested lands prior to extensive

and intensive animal surveys may have caused species extinctions prior to their discovery. Another possibility for the undercount could relate to the fact that more

research still needs to be conducted. A current example of this possible undercount

of species is illustrated by the All Taxa Biodiversity Inventory currently taking

place for the first time in the Great Smoky Mountain National Park in Tennessee.

This will require an estimated 15 years of full-scale work in an area of only 202

429 hectares (500,000 acres). That study is only at its developmental stage and has

already produced numerous new species (76) and new species records (557) for the

park. A similar program is being conducted on Navassa, an uninhabited forested

island 60 kilometers (36 miles) west of Haiti, by the Caribbean Biodiversity

Program of the Center for Marine Conservation in Washington, DC. Estimates run

as high as 250 new species to be identified from this island, which is only 5.2

square kilometers (2 square miles) (Science 1998). Puerto Rico undoubtedly would

yield many new finds should such a study be conducted on such a diverse island

landscape. According to Helmer et al. (2002), tropical areas with complex topography are particularly important for biodiversity conservation. Tropical mountainous

areas made up 11 of 25 biodiversity “hotspots,” and 7 hotspots included or consisted of complex tropical islands (Myers et al. 2000). According to Myers et al., the

Caribbean region is one of the hottest hotspots where 11.3 percent of the region’s

original primary vegetation contains 2.3 percent of the world’s endemic plants and

2.9 percent of the vertebrates.

As far as terrestrial vertebrates are concerned, the birds are the largest group by

species numbers (see section on “Birds” of Puerto Rico that follows). The second

46

General Technical Report IITF-35
largest group is reptiles. Mammals are third, followed by amphibians. These rankings include introduced species (table 10).

The Antilles Islands’ bird life is probably the best known of any section of the

Neotropics. According to Bond (1971), the avifauna of the West Indies is predominantly North American tropical, with its greatest connection to the Central

American bird groups. There is also very good representation of the continental

North American groups owing to the winter range of Neotropical migratory species

(see section on Neotropicals that follows). Two bird area groups or provinces represent the Greater Antillean province and the Bahamian-Lesser Antillean province.

Puerto Rico has no endemic bird families, and less than 1 percent of the genera are

endemic. However, it does have 14 endemic species. 

On the other hand, Puerto Rico’s herpetofauna (amphibians and reptiles) is

highly endemic. Only seven (9.2 percent) of its native species are found in other

island systems. They are mostly related to genera from the Greater Antillean chain.

Five genera are exclusive to the Greater Antilles, with the Puerto Rican crested

toad (Peltophryne lemur) a good example. The other 11 genera are primarily

Greater Antillean. According to Thomas and Joglar (1996), there are 80 species 

of amphibians and reptiles in Puerto Rico, 90 percent native and 10 percent introduced this century. No genera of amphibians and reptiles are endemic to Puerto

Rico. Puerto Rico has no species of true salamanders (order Caudata). There is 

a gecko (Hemidactylus spp.) called “salamander,” but it is a lizard.

There are four amphibian frog and toad families present: Bufonidae, 

Hylidae, Ranidae, and Leptodactylidae. This latter family includes the genus

47

Guide To The Ecological Systems Of Puerto Rico

Table 10—Vertebrate species by major group

Group Species

Birds (class aves): 269

(50 families)

Reptiles (class reptilia): 54

Turtles 6

Snakes 9

Lizards 38

Crocodiles (introduced) 1

Mammals (class mammalia): 32

Bats 14

Marine (manatees, whales, porpoise) 8

Introduced (mongoose, rats, etc.) 10

Amphibians (class amphibia) 25

Toads 2

Frogs 23
Eleutherodactylus (tree frogs), which has 16 species in Puerto Rico, with numerous

endemics (see section on “Tree Frogs” that follows). The family Bufonidae (toads)

has only two species present, the endemic Puerto Rican crested toad (Peltophryne

lemur) and the notorious giant marine toad (Bufo marinus). Bufo marinus was

introduced to control the white grub that attacks sugarcane. As has been the case so

many times in the past, this well-intentioned introduced alien is now naturalized

and has spread throughout the island. It can grow to the size of an average man’s

foot. The Ranidae consists of one genus and species, Rana catesbeiana (bullfrog).

This, too is an introduced alien species.

The class Reptilia (reptiles) has three orders present: Chelonia, Squamata, 

and Crocodilia. Chelonia includes the turtles and tortoises; Squamata includes 

the lizards and snakes; and the Crocodilia includes the crocodiles, alligators, and

caimans. In Puerto Rico, the Squamata is the largest reptile group and includes six

families of lizards, with 38 species present. There are three families of snakes, with

nine native species. Both groups include alien species. The large common green

tree iguana (Iguana iguana) is now found in many places in Puerto Rico. It is

native to Central and South America and was introduced via the pet trade. It is not

uncommon to see individuals greater than 1 meter (3 feet) in length along roads or

in trees. They can grow to 2 meters (6 feet). They look fierce, but in fact are harmless and primarily herbivorous. There are at least three introduced snakes, including the common watersnake (Natrix sipedon) and the common garter snake

(Thamnophis sirtalis) from the United States, and the African python (Phyton

regius). Undoubtedly, there are other released and escaped snake species that are

present, but to date not naturalized. The native snakes include three members of the

Boa family (Boidae). The Puerto Rican boa (Epicrates inornatus) is endemic to 

the island. It is the largest native species attaining a length of 3.6 meters (12 feet).

Most are less than 2 meters (6 feet). Its population is now restricted as a result of

earlier massive habitat destruction. It is most common in the karst areas of the

north coast and the volcanic Luquillo Mountains, although it occasionally shows up

on the dry south coast. Its color varies from dark brown to tan, with crossbars or

spots present. It uses the ground and trees while feeding on rats, mice, and bats. It

will consume frogs, lizards, and insects. They in turn are preyed upon by hawks,

domestic pigs, and cats. Puerto Rico also has blind or worm snakes (of the genus

Typhlops), which are subterranean and feed extensively on ants and termites (see

the section on termites that follows).

The lizards constitute the largest group of the Reptilia. This group includes the

geckoes, anoles, iguanas, skinks, and blind lizards. The genus Anolis is quite large

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General Technical Report IITF-35
with an estimated 300 species, 11 of which are present in Puerto Rico. This is the

lizard group most observed by students and visitors alike. They seem to be everywhere. They come in a variety of colors and their colors can change as the background color changes. Some are bright chameleon green. The most common

species is Anolis cristatellus, commonly found in houses and nearby vegetation.

The males are larger than females and have flexible colored dewlaps (expandable

lower throat-neck skin) that they use in defense and courtship (fig. 8). They prey

on a variety of insects and use the sit-and-wait technique of hunting. They in turn

are prey to a variety of birds, the larger of their own species, and snakes. They are

abundant in many habitats, from the coast to the high mountains, and some of the

species are altitudinally zoned. They are diurnal and appear to occupy roughly the

same niche diversity as birds do in larger continental systems in terms of habitat

zonation, feeding, and microclimate preferences. They consume vast quantities of

insects. The larger (body size) species group hunt over greater distances and consume larger prey. The smaller species seek out smaller prey over shorter foraging

distances.

The Chelonia representatives in Puerto Rico consist of six species of turtles. 

Of the six species, only one is native and freshwater, Trachemys stejnegeri (locally

called, hicotea). It is omnivorous and inhabits lowland freshwater habitats such as

rivers, lagoons, and ponds. It is uncommon, but can be found in Lake Tortuguero

49

Guide To The Ecological Systems Of Puerto Rico

Figure 8—A green Anole (Anolis cuvieri) with its brilliant dewlap expanded. 

L. Miranda Castro
and drainage ditches in the Guánica area. It grows to about 25 centimeters (10

inches). The locals love its good tasting meat. Two introduced species of freshwater

turtles are in Puerto Rico. They arrived via the pet shop trade. They are Trachemys

scripta (red-eared turtle) and Chrysemys picta (eastern painted turtle). Their reproductive status and population distribution are poorly understood. The remaining

turtle species are sea turtles and are all listed as endangered species. The two most

important to Puerto Rico are Chelonia mydas (green sea turtle) and Caretta caretta

(loggerhead turtle). Both have been heavily overfished this past century and are

still being taken illegally, in spite of their protected status. These were all-purpose

animals prized for their meat and shells, which could be made into useful objects

such as jewelry (bracelets, earrings, necklaces, and hair pins). Possession of any

part of these animals today can result in a substantial fine and even jail time. Green

turtles used to be common to coral reefs and seagrass beds prior to the 1970s.

Today they are rarely seen as a result of fishing pressures and loss of nesting habitat. For more information on the status of these two sea turtles, see Ehrhart et al.

(1991 and 1993). There are a variety of educational wall charts and brochures

available from government agencies describing sea turtles and their protected 

status. (See app. 4 for contact information). There are no native resident populations of tortoises, but some pets have likely been released in various places in

Puerto Rico.

The third order in the Reptilia is the Crocodilia. Puerto Rico has only one

species from this group, the introduced Caiman crocodilus (spectacled caiman). It

is a species found in Central and South America and was released in Puerto Rico as

a result of pets that grew too large to be accommodated by their owners. There are

now four known populations in Puerto Rico, with one of them at Tortuguero

Lagoon (see the “Wetlands” section). Caiman crocodilus can attain a length of 2.6

meters (9 feet), although most are less than 1.8 meters (6 feet). It gets its name

from the presence of a bony ridge between its eyes that resembles the nosepiece of

eyeglasses. The spectacled caiman is a popular reptile sold in the animal trade,

especially after the United States designated the American alligator (Alligator mississippiensis) legally protected under the Endangered Species Act. For a complete

review of the amphibians and reptiles of Puerto Rico, see Rivero (1998). Joglar

(1998) presented a review of the amphibians, with special attention to the genus

Eleutherodactylus, in his book The Coquies of Puerto Rico: Their Natural History

and Conservation.

The mammal fauna in Puerto Rico is quite depauperate. The largest terrestrial

group is the bats, with 14 species (see section on bats that follows). The next

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General Technical Report IITF-35
largest group is the marine mammals of which there are 10 species that can be

found in waters in the vicinity of Puerto Rico. This group includes whales, 

dolphins, and porpoises. There are at least eight alien terrestrial mammal species 

in Puerto Rico, including rats, mice, mongoose, and four species of monkeys. 

The mongoose was introduced from Jamaica (origin is India) to control rats.

Unfortunately, it did not control the rat population, but it did become a pest in its

own right and is a major predator of native birds and reptiles. The mongoose is

active during the day, whereas the rat is most active at night. The monkeys escaped

from rearing colonies of the Caribbean Primate Center for use in medical research.

On occasion, small troops can be seen crossing roads and feeding in trees on the

south coast. Puerto Rico recently received a large grant to be used for the recapture

of the monkeys. Some domesticated mammal species have escaped and these feral

populations are reproducing. According to Waide (1987), the introduction of mammals to islands with no native mammals has historically been most destructive for

native wildlife.

The last native terrestrial mammals of any size were the giant tree shrew and a

large rodent. The giant tree shrew (Solenodon paradoxus) has not been seen since

the early 1800s. It is thought to be extant in Cuba. It was a large insectivore. The

large rodent, Isolobodon portoricensis, has not been seen since the early 1800s.

Again, it is thought to be extant in Cuba, but on the verge of extirpation. The fossil

record also showed another 10 or so mammal species that were present in Puerto

Rico in the past.

In the freshwater and marine environments around Puerto Rico and east 

to the U.S. Virgin Islands, there are nearly 800 fish species from the classes

Chondrichthyes and Osteichthyes. The fish fauna of Puerto Rico is a complex mixture of Atlantic, Caribbean, and alien species. The north coast has a narrow shelf,

with deep water near shore and the coastline receiving heavy surf. It has little coral

or well-developed seagrass beds. The south coast’s shelf is wider with lots of fringing reefs, seagrass beds, and adjacent mangrove swamps. The south coast receives

much less heavy wave action off the Caribbean, especially in the winter. The 

freshwater fishery has a number of human introductions associated with it. The

Chondrichthyes (cartilaginous fishes) include the sharks, dogfish sharks, skates,

and rays. There are 20 species of sharks and rays in Puerto Rico’s waters. The

Osteichthyes are the true bony fishes, of which there are more than 18,000 species

worldwide (some estimates run as high as 40,000 species). They represent the

largest group of vertebrates and comprise about half of the world’s species of living

vertebrates. There are 80 freshwater fish species and nearly 300 marine species

51

Guide To The Ecological Systems Of Puerto Rico
common in Puerto Rico. Most species are associated with coral reefs. In 1970,

Puerto Rico had an estimated 1,000 commercial fishermen, 400 full time. At that

time, Puerto Rico produced around 2.4 million pounds of shellfish and fish.

Virtually all of it was consumed locally. It was valued at $780,000. Even then,

when the coral reefs were in good condition (see “coral reefs” section), Puerto Rico

was importing $24 million in fish and shellfish from the United States. There are

many fewer fishermen today, and the island is even more reliant on imports to satisfy its seafood demand. Many commercially valuable species such as Caribbean

lobster, grouper (bluehead wrasse), and snapper can only be found in more distant

and deeper waters.

Of the 80 freshwater fish species, 20 are alien species introduced for sport 

fishing and food. These include two species of bass (Micropterus spp.), three

species of sunfish (Lepomis spp.), and four species of catfish (Ictalurus spp.).

Numerous species of tropical aquarium fish, such as guppies, swordtails, and 

mollies, have been imported and subsequently released and introduced to the rivers

and lakes of the island. There are also species such as the American eel (Anguilla

rostrata), which grows to an adult in freshwater rivers and then returns to the sea

for reproduction. These organisms are referred to as catadromous. They exhibit a

fantastic migration to the Sargasso Sea where they spawn and die. Their offspring

then return to freshwater completing this long roundtrip journey. Freshwater trout

(Salmo spp.) were also introduced in 1938 via a trout hatchery established in

Maricao, but because the water temperatures are too high, their introduction did 

not take. Table 11 presents some of the alien animals now found in Puerto Rico 

and some of the problems they are producing.

See appendix 2 for suggestions on viewing animals in Puerto Rico. For further

reading on the fauna of Puerto Rico, see Diaz 1983, Erdman et al. 1985, Erdman 

et al. 1986, Martin and Patus 1984, Nellis 1999, Nieves 1980, Thomas and Joglar

1996, Torres 1994, Torres and Gaud 1998, Wallace 1989, and Wolcott 1948.

Tree Frogs

Puerto Rico has 23 species of frogs, of which 16 belong to the genus Eleutherodactylus, the group known as the tree frogs. They are unlike many other amphibians in that they do not have to return to water to complete their life cycle. They do

not produce a free-living, water-requiring tadpole stage, but instead undergo rapid

direct development to the adult stage. They are referred to as coquíes because of

their calls, and specifically E. coqui whose call sounds like its genus name (Kokey). Wherever you go in Puerto Rico from dusk to early morning you are likely to

52

General Technical Report IITF-35
hear the chorus of coquíes calling. Their call is almost the national anthem. The

animal is the unofficial national symbol, in that it appears in fine jewelry shops as

necklaces and pins, and on schoolkids’ backpacks and t-shirts. The coquí is the 

animal most identified with in Puerto Rico and results in millions of dollars in 

sales of coquí products to islanders and tourists alike.

These small vertebrate animals are primarily insectivorous. Each species has a

niche, and each niche has specific insects living there. Some feed at the base of tree

trunks in the litter zone, whereas others use the trunk, branches, and leaves. Males

usually feed higher up and usually will make their calls from a different location

above the location of the females. Most are nocturnal, but they can be located during the day. At night they are easily spotted with a spotlight as you zero in on their

calling position (see app. 2 for information on how to catch a tree frog).

Eleutherodactylus coqui is endemic to Puerto Rico and is found throughout the

island. It is the second largest of the lowland species and is usually brown, to graybrown, and it may be mottled. They sometimes have a w-shaped mark on the nape

and a chevron mid-back. They frequently show a dorsolateral band and a stripe

53

Guide To The Ecological Systems Of Puerto Rico

Table 11—Examples of alien animal species in Puerto Rico

Common

Scientific name name Location Problem

Macaca mulatta Rhesus monkey Southwest Will bite while being captured; may 

become major predator of local species

Herpestes Indian Islandwide Major competitor to anything smaller

auropunctatus mongoose 

Rattus rattus Black rat Islandwide Major competitor to anything smaller; 

preys on eggs and young of birds, 

including the endangered Puerto Rican 

parrot

Iguana iguana Common iguana Islandwide Crop destruction

Caiman crocodilus Spectacled Tortuguero Possible threat to humans—as subadults 

caiman Lagoon and adults

Python regiusa African python Caribbean Constrictor; could take domesticated 

National Forest animals

Margarops fuscatus Pearly-eyed Islandwide Threat to native birds, especially Puerto 

thrasher Rican parrot and other cavity nesters; 

may have contributed to extinction 

of white-necked crow (Corvus 

leucognaphalus) in 1960s

Micropterus salmoides Large-mouth Freshwater Top of aquatic food chain; could affect 

bass native fish species

Apis mellifera Honey bee Islandwide Interferes with bird nesting—for 

example, endangered Puerto Rican 

parrot

a Not known to be a reproducing population.
that may extend laterally to their knees. They are nocturnal and frequently inhabit

tank bromeliads and curled leaves. They call at night and forage from the ground to

the subcanopy (fig. 9). Males are territorial and they will defend their territory by

biting and butting male invaders. Once a male attracts a female, amplexus occurs.

Fertilization is internal and eggs are laid in nests of curled leaves. Typical nests

will bear 26 eggs in the clutch and the male will provide parental care, which

includes brooding and defense. Brooding maintains the needed moisture level and

prevents desiccation. Egg and young predation occurs from other coquíes and

invertebrates. Juvenile frogs develop directly without a tadpole phase in 17 to 26

days. Coquíes are very sedentary and will maintain the same territory for several

years. Movement is usually associated with moving to calling perches and foraging. Coquíes are sit-and-wait predators of insects. Their vast numbers, coupled with

the other species of amphibians and reptiles, make the herps the major predators of

the forest. It is interesting that while in many areas of the world amphibians are in

decline, not so in Hawaii. In the last decade, two small Caribbean frogs were introduced (probably on plants) and they have successfully invaded a number of the

islands. Hawaiians want them eradicated because their vocalizations are perceived

as noise. Most people of the Caribbean love their calls and generally find their

melodic choruses sleep inducing.

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Figure 9—Eleutherodactylus coqui (coqui) calling.

J. Puente Rolón
For further reading see Joglar 1998, Reyes 1971, Rivero 1998, Schwartz 1991,

Stewart and Pough 1983, Townsend and Pough 1984, Woolbright 1985. The Joglar

reference has very good closeup photography of adults, egg masses, habitats and

range maps, and Drewry’s vocalization descriptions.

Birds

Herbert Raffaele (1983) in his Guide to the Birds of Puerto Rico and the Virgin 

Islands indicated the avifauna of Puerto Rico consists of 269 species. There are 

50 bird families and 149 genera. Ninety-five of the species are permanent resident

breeders, 126 species are nonbreeding migrants or visitors, 36 species are introduced aliens, 11 species use Puerto Rico for breeding, and 1 recently became

extinct (white-necked crow [Corvus leucognaphalus]). Puerto Rico’s avifauna

diversity is second only to that of Cuba for the West Indies. It has the largest number of breeding alien species of any island in the West Indies. Why so many aliens?

In Puerto Rico, many people have pet birds, resulting in many escapes as a result

of the pet trade. For instance, the Dominican parrot population has been exploding

in many areas. It is a very popular house pet and many escape into the wild. In

addition, habitat alteration in the past 150 years has produced a considerable

increase in grassland habitats and crop fields. This has resulted in a tremendous

increase in edge habitat. Puerto Rico has many more seed-eating birds needing

grassland or crops today than 150 to 200 years ago when forests dominated the

landscape.

Puerto Rico has 14 endemic bird species (fig. 10) which include the:

➢ Puerto Rican parrot (Amazona vittata)

➢ Puerto Rican whip-poor-will (Caprimulgus noctitherus)

➢ Puerto Rican lizard cuckoo (Saurothera vieilloti)

➢ Puerto Rican tody (Todus mexicanus)

➢ Puerto Rican woodpecker (Melanerpes portoricensis)

➢ Puerto Rican tanager (Nesospingus speculiferus)

➢ Puerto Rican hummingbird (Anthracothorax dominicus)

One genus, Nesospingus (tanager), is found only in Puerto Rico’s higher mountain forests, mainly in El Yunque and the Maricao Commonwealth Forest. The

presence of endemics such as these makes for an interesting discussion of island

biogeography, species dispersal, niche, speciation, and disjunct populations. Of

great interest to humans today is the whole issue of species extinction and the problems that humans produce in the natural world, which can lead to animal and plant

endangerment. In the case of birds, islands are at the heart of this debate because

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Guide To The Ecological Systems Of Puerto Rico
more than 75 percent of all bird extinctions have occurred on islands. Why? Very

simply, islands are usually small, and thus many organisms found on islands have

no additional habitat to escape to when their primary habitats are altered. In other

cases, they have narrow specializations owing to their development in isolation,

and may have no defense when new alien predators are introduced or humans

decide to “use” them or exterminate them. Many are not exceptional flyers, thus

there can be little chance for successful migration to new distant habitats. In some

cases, island-dwelling birds may lose their immunity to disease, and as new organisms invade or are introduced by humans, diseases are introduced. Most bird

extinction in the Caribbean is associated with humans and not alien species.

In the case of birds, the three most important causes of endangerment are habitat loss, introduced alien species, and hunting. In some cases all three may simultaneously affect a species, as was the case with the endangered Puerto Rican parrot.

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Figure 10—Four of the endemic birds of Puerto Rico: (a) Puerto Rican emerald (Chlorostilbon maugaeus), (b) Puerto Rican tody (Todus mexicanus), (c) Puerto Rican screech owl (Otus nupides), and 

(d) Puerto Rican parrot (Amazona vittata). 

A

C D

B

Photos a-c by L. Miranda Castro, Photo d by T. Carlo
Raffaele (1983) reviewed extirpations, both pre- and post-Columbian, and cited the

current reasons for species being classed as threatened (T) or endangered (E). Of

the 269 birds in Puerto Rico, 51 species are classed as either T or E. This represents 22 percent of the total. The vast majority is being severely affected by habitat

disturbance or destruction (49 species). Seventeen species are affected by hunting,

and three by the introduced mongoose or rats. There is overlap in these statistics, as

some species may be affected by two of the population reduction factors. For

example, all six species of breeding ducks were suffering from drainage of freshwater wetlands and, at the same time, they were being hunted. It is only recently

that Puerto Rico has developed and enforced hunting laws for protected species.

Enforcement continues to be a problem. There is need for additional officers in the

field. In addition, some hunted species have well-defined seasons for breeding,

whereas others do not. Thus, when some species are being legally hunted, others

are breeding, which results in breeding interruption by guns, dogs, boats, and so

forth, for some species. Six bird species have been introduced for hunting, for

example, the partridge. About 75 species in Puerto Rico are used for sport or food.

In other cases, growth of population centers and tourism is resulting in both habitat

destruction and interruption of breeding in remote beaches, offshore islands, and

mangrove swamps. Also, although it is illegal, many wild birds are kept in cages as

house pets.

Bird sanctuaries have not been well developed or secured until recently. Major

U.S. government sanctuaries exist in the El Yunque National Forest, the Cabo Rojo

National Wildlife Refuge, and other national wildlife refuges at Laguna Cartagena,

Desecheo Island, and Culebra. Commonwealth of Puerto Rico refuges have grown

out of the 14 commonwealth forests, with Guánica especially significant to

Neotropical migrants described in the section that follows. Additional sanctuaries

have been developed at Boquerón Forest, Aguirre Forest, Piñones Forest, Humacao

Refuge, Las Cabezas Reserve in Fajardo, Caja de Muertos Island Reserve, and the

Boquerón Bird Refuge. All totaled, there are 13 commonwealth refuges on the

island.

As throughout most countries of the world, ecological interest in birds and bird

watching as an avocation is growing in Puerto Rico. Today, Puerto Rico has active

bird watching clubs and a growing ecotourism industry that offers specialty trips

centered on the island’s wildlife. Mixed populations of exotic parrots, including 

the brilliantly colored macaws can be seen at the University of Puerto Rico’s main

campus in Río Piedras. Hundreds may be there at any given time. They are frequently in the area between the bell tower and the student union. You find them by

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Guide To The Ecological Systems Of Puerto Rico
listening for their calls and chatter. They get to be quite loud! They all result from

escapes or releases from homes or pet stores.

For places to bird watch, see app. 2. For further reading see Bond 1971, Nellis

1999, Oberle 2000, Philibosian and Yntema 1977, and Snyder et al. 1987.

Neotropical Migrants

In his poignant book titled Where Have All The Birds Gone? John Terborgh (1989) 

of Princeton University brought to the world’s attention the fact that birds do not

respect political boundaries and that they may reside in a series of countries in their

long migrations to and from summer breeding and wintering areas. They are creatures of instinct and as such migrate according to the complex rhythms of nature.

They are the birds that may be the summer songbirds in people’s backyards or interior forests in eastern North America, and the winter songbirds in coffee plantations or dry forests of the American tropics—thus the term Neotropical migrants.

Unfortunately these birds are under enormous pressure, and their populations are

succumbing to a variety of stressors, chief among these is habitat destruction on

both ends of the migration routes. Terborgh pointed out that even though bird populations have changed drastically in some areas of the Eastern United States, the

physical places themselves have not. This raised the question of “Why?” Today, of

course, we know why. In some instances it was the drastic alteration of habitat in

the tropics, in other cases it was fragmentation of forests in the temperate zone.

Following is a partial list that can account for most of the changes in Neotropical

species populations.

Agents of stress include:

➢ Habitat destruction

➢ Forest fragmentation with increased edge

➢ Introduced species

➢ Pesticides

➢ Technology effects (lights, vehicles, and so forth)

➢ Changing agricultural practices

➢ Increased numbers of feral domestic cats

➢ Loss of riparian zones

➢ Destruction of wetlands

➢ Changing silvicultural patterns

➢ Monocultures

➢ Towers (power, radio, TV, phones)

➢ Highrise buildings

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General Technical Report IITF-35
➢ Large plate-glass doors and windows

➢ Lack of fire or too much fire in the landscape

➢ Disease

➢ Nest predation

➢ Switching from shade- to sun-grown coffee

The genesis for Terborgh’s book was a winter holiday to Puerto Rico in the 

late 1960s. It was during this first trip to the tropics that he noticed that many of

the birds typical of the Middle Atlantic States were spending the winter in Puerto

Rico, especially certain species of warblers, water thrushes, and ovenbirds. That

was the advent of the study of Neotropical migrants. Over the years he has been

tracking the status and destination of some 250 migratory species that spend time

in 15 tropical countries. Surveys were conducted in habitats ranging from rain

forests to deserts, and from coastal mangrove forests to mountaintop elfin forests.

One of the primary sites where Terborgh and his colleague at the USDA Forest

Service, International Institute of Tropical Forestry (Wayne Arendt) conducted

some of their initial research is the Guánica Commonwealth Forest (see app. 2, 

p. 373). Neotropical migrant surveys are still going on, and in any given January

you are likely to see crews in the field sampling extensive arrays of mist nets as

they stretch through various sections of the Guánica Forest. 

Today, there are many groups working on the Neotropicals issue, including the

U.S. Fish and Wildlife Service, the USDA Forest Service, and their counterpart

agencies in Canada, the countries in the tropics, and the various state government

groups in the United States and Puerto Rico. There are numerous nongovernmental

organizations (NGOs) also vitally involved including the National Audubon

Society, The Nature Conservancy, and The National Fish and Wildlife Foundation,

to name just a few. Many public and private agencies cooperate in the Neotropical

Migratory Bird Conservation Program, also called “Partners in Flight.” This program was initiated in 1940 to promote Neotropical bird research, develop conservation programs, and promote habitat protection and enhancement. Cooperative

programs are also in development with the counterpart agencies and NGOs in the

birds’ winter range countries.

The effort to protect these species must truly be an international effort. Without concern and efforts on both ends of this delicate migratory chain, conditions

will only worsen. To be sure that half the birds that breed in the United States and

Canada, and spend 6 to 9 months in the Neotropics, have the chance to continue

these ancient migratory patterns, we have to reduce those agents of stress mentioned earlier. In addition, Neotropicals are at a distinct disadvantage reproductively

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Guide To The Ecological Systems Of Puerto Rico
because many are small bodied and have difficulty in defending nests from predators. Many build open ground nests where they are more subject to detection. Many

have difficulty in producing a second brood if the first is lost owing to weather,

predation, or parisitism. Some species may not breed at all if the special requirements for isolation in the interior of extensive forests of critical stand age are 

not met.

Some migratory birds are permanent residents, that is, they stay put and do not

migrate except for very short distances (Cardinals [Richmondena cardinalis] and

Blue jays [Cyanocitta cristata] in North Carolina, Puerto Rican parrot [Amazona

vittata] in Puerto Rico). They are able to cope with a variety of changing habitat

conditions, and all their resource needs are met in one geographic area. Other

species are short-distance migrants, that is, they move from mountain habitats to

valleys as the seasons change, such as slate-colored Juncos (Junco hyemalis) or

Robins (Turdus migratorius). True migrants may migrate great distances, thousands

of kilometers (miles) or more, in order for their life cycle needs to be met as in 

red-eyed vireo (Vireo olivaceus). The common ruby-throated hummingbird makes 

a nonstop journey of 1300 kilometers (800 miles) to cross the Gulf of Mexico to 

its winter range in Central America. Long-distance migratory species require a vast

storage of energy (up to 50 percent of body weight) or frequent refueling stops

along the way in order to supply the energy necessary for the long distances to be

traveled (fig. 11). Twenty-eight species of shorebirds have been recorded in Puerto

Rico, 24 of which are migrants. Fourteen waterfowl species that breed in North

America spend their winters in Puerto Rico, including Mallards (Anas platyrhynchos), blue-winged teal (Anas discors), American widgeon (Mareca americana),

and pintails (Anas acuta). A total of 132 Nearctic-Neotropical migrants have been

identified in Puerto Rico (Watson and Martínez 2002.)

There are some distinct disadvantages to migration, so why migrate?

➢ It permits the birds to avoid the cold periods in the northern climates 

and hot/humid periods in the tropics.

➢ It reduces intra and interspecific competition for food in the winter 

pinch period at a time when the total bird population would be highest, 

that is, after the breeding season.

➢ It provides for opportunistic feeding during migration.

➢ The changing day lengths in the north greatly hamper food availability 

in the winter.

➢ Long daylight periods during the breeding season foster access to more

food supplies.

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Guide To The Ecological Systems Of Puerto Rico

Figure 11—Neotropical migrants use a variety of fly ways to reach their summer/winter range destinations.
➢ It provides genetic advantages of large mixed populations, not just those 

of one highly restricted area.

➢ It allows ecosystem recovery in areas not continuously occupied 12 months

a year by the entire bird assemblage.

As previously cited, there are many stressors of Neotropical migrant populations. One that is producing great habitat change in the tropical mountain agroecosystems is the switch from shade-grown to sun-grown coffee. This relatively

simple shift in cultivation practice may be responsible for substantial declines in

Neotropical migrants. Coffee has traditionally been grown under a canopy of other

trees including citrus, breadfruit, bananas, nut-producing trees, and others. Mature

trees full of epiphytes and lianas provide many microhabitats for a diverse animal

community. Most coffee grown in the New World (32 percent of world production) comes from northern Latin America where coffee lands make up approximately 44 percent of the permanent crop land (Perfecto et al. 1996). New varieties

of sun-loving coffee give higher yields per plant; as a result, the old plants are

being replaced with new varieties, and the canopy species are being cut, highly

simplifying the ecosystem. In addition, in this newly created coffee monoculture,

more pesticides and fertilizers are required to produce the desired yields. Half of all

shade-grown coffee has been replaced with sun-grown coffee. Environmentally

friendly coffee companies can market shade-grown varieties and pay premium

prices for them, thus encouraging coffee farmers to preserve existing shade coffee

plantations and return coffee plantations to shade. They also give purchasing preferences and price incentives to vendors who grow coffee in accordance with the

Conservation Principles for Coffee Production. These principles emphasize protection of biodiversity, soil conservation, water quality, minimization of agrochemical

use, and appropriate waste management (Johnston 2001).

The previous multilevel shaded agroecosystem supported many more species

of birds, with some studies indicating 150 species or more. As Wunderle (1997) 

put it, “diversity begets diversity,” that is, structural diversity of the vegetation promotes a biologically diverse animal community, thus contributing to a rich biologically diverse coffee plantation. In addition, these plantations may serve as refugia

for forest-dwelling birds in a region that may be largely agricultural including

native nonmigratory species. In the new simplified sun coffee plantation monocultures there is a drop in both total species present and numbers of individuals of a

species. In some areas there has been a 90 percent decline in species presence. In

Puerto Rico, where little shade-grown coffee land has been converted, the traditional coffee plantations are thought to have served as a critical refuge during a

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General Technical Report IITF-35
human-caused habitat bottleneck. It appears that Puerto Rico experienced a low

rate of avian extinction during recent periods of deforestation owing in part to their

traditional agroecosystem plantations acting as refuges. Not only was bird loss

minimized, it appears that rare orchids also survived on the coffee farms. The 9

percent of the island covered in traditional coffee served as a refuge even though

99 percent of the original forest had been destroyed or disturbed (Perfecto et al.

1996).

Coffee is the world’s most widely consumed beverage; therefore, it has wide

economic impact all the way through its delivery system. At all levels, various

business people are making bottom-line decisions based on yield, supply, and profits. With slim profit margins, any increase in yield or profit is bound to produce

pressure to switch to sun-grown coffee. Unfortunately, the short-term decision is

likely to produce increased erosion, greater reliance on expensive chemicals, loss

of water quality, and substantial long-term effects on the animal community, especially Neotropical migratory birds. The cost of operating coffee plantations also

increases, and in cases, leads to bankruptcy.

Why should you be concerned about Neotropical birds?

➢ They eat vast quantities of insects.

➢ They disperse seeds for many plants.

➢ They are beautiful.

➢ Their songs are wonderful to listen to.

➢ Their migration ability represents one of the true wonders of nature.

➢ They are part of the complex web of life.

➢ Their place in the web of life is not completely understood.

For further reading on Neotropical migrants, see Franzreb and Phillips 1996, 

Raffaele 1983, Rappole 1995, Tangley 1996, Wille 1994, and Wunderle and Latta

1996.

Bats

Bats dwell in the secret world of the night. As a result of much misinformation, 

they are feared by many and poorly recognized for the vital roles they play in many

ecosystems around the world, especially in the tropics. Mythology, world folklore,

popular literature (Stoker’s Dracula), and Hollywood movies have contributed to 

a reputation that portrays bats as evil and spreaders of disease. They fly at night,

some live in caves (the netherworld) and, yes, some even suck blood (less than 1

percent). Thus, for many people “the only good bat is a dead bat.” The truth is that

these small flying mammals from the order Chiroptera (which means “handwing”)

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Guide To The Ecological Systems Of Puerto Rico
should be treasured because of all the good they do in nature. Some fruit-eating

bats have wingspans approaching 1.8 meters (6 feet). The smallest bat is the bumblebee bat of Thailand, weighing less than a U.S. penny.

Many cultures have historically valued bats. In China they are a sign of 

happiness. In México and northern South America, they are a sign of fertility.

Unfortunately, throughout much of Europe and North America they are associated

with death, disease, blood sucking, and evil and are thus highly persecuted and

classed as a pest. Some people think they are blind (“as a bat”), but in fact they

have a highly evolved form of “vision by sound” called echolocation. This allows

bats to locate prey, walls, vegetation, or whatever is in their path with extreme

accuracy. They emit high-pitched sounds and then detect the echo that rebounds

from any structure or organism in their flight path. Some can discriminate between

echoes arriving only two-millionths of a second apart and can echo-separate objects

that are only 0.3 millimeter (less than 1/90 of an inch) apart. These abilities are

three times better than current military sonar, according to James Simmons of

Brown University (1998).

Bats are the only flying mammals and are distributed all over the world. They

comprise 25 percent of all mammal species and currently include nearly 1,000

species. Eighty-eight percent of all bat species are found in the tropics, mostly the

Neotropics. There are as many bats in the tropics as all other mammal species combined. Their value is enormous and without them some species and whole ecosystems would be in jeopardy. Why are they valuable?

➢ They eat vast numbers of insects and rodents (70 percent of species are 

carnivorous and eat up to 50 percent of their body weight in one evening).

➢ They serve as primary pollinators for thousands of tropical plants while

searching for nectar, pollen, and fruit (30 percent of species). Below are

just a few of the plants that bats pollinate:

➢ Bananas ➢ Figs ➢ Kapok

➢ Mangoes ➢ Cashews ➢ Agave

➢ Guavas ➢ Cloves ➢ Peaches

➢ Avocadoes ➢ Cacti ➢ Durians

➢ Dates

➢ They are fruit eaters that vector seeds throughout their range.

➢ They supply large quantities of guano fertilizer.

➢ They are important to research on blood clotting factors 

(anticoagulents produced by blood-sucking species).

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General Technical Report IITF-35
➢ They are important to research in antibiotics because they show 

few diseases.

➢ They are important to ecotourism; many people are recognizing 

their ecological importance and want to see them and their habitats.

➢ Sonar research is looking at their exceptional ability to locate objects 

in flight.

Because of their vital importance in both pollination and seed distribution,

bats are considered keystone agents. Should bats disappear or decline, other

species would likewise decline or disappear. Their influence on the community or

ecosystem is much larger and more influential than you would expect from their

presence or abundance alone. Humans derive 450 commercial products from 

bat-dependent plants. 

Unfortunately, wherever they are found, bats are under attack. Threats to their

survival include:

➢ Lack of understanding of their value

➢ Disturbance of roosts such as caves by cavers, hikers, and researchers.

Disturbances cause young to drop from the cave’s ceiling and adults to 

fly and use up food reserves in winter periods.

➢ Habitat destruction (deforestation, fire, cutting snags in forests)

➢ Destruction of their food supply

➢ Food chain contamination with pesticides (DDT)

➢ Being classed as vermin in most countries and killed on sight

➢ Being eaten as human food in the Far East

➢ Vandalism whereby people intentionally disturb roosts or destroy 

habitat

➢ Flooding owing to hydroelectric dam construction

Puerto Rico has 14 species of bats. Some tend to be more coastal, such as the 

bulldog fishing bat (Noctilio leporinus), seen at Boquerón on the southwest coast

where it feeds on insects and fish. It roosts in hollow trees and caves. Others, such

as the endemic red fig bat (Stenoderma rufum) will be found in the tabonuco montane rain forest where it is a frugivore (fruit eater). It is classed as a sensitive

species by the U.S. Fish and Wildlife Service. The tabonuco forest has populations

of seven bat species, with the red fig bat accounting for nearly 25 percent of the

total bat population (fig. 12). Eleven of Puerto Rico’s 14 species are associated

with the El Yunque National Forest (Weaver 1994). The largest bat found in Puerto

Rico is the Jamaican fruit bat (Artibeus jamaicensis). As its common name implies,

it is a frugivore, but it will also feed on insects. Four of Puerto Rico’s bats feed

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Guide To The Ecological Systems Of Puerto Rico
mainly on fruits, pollen, and leaves. The others feed primarily on insects and fish.

The majority of bat species roost in cool caves, and Puerto Rico has a vast network

of caves, especially in the karst region on the north side of the island where roosting habitat is almost unlimited (see app. 2, p. 373). The karst belt is home to 13

species of bats, 10 of which use caves as preferred roosting sites (Rodríguez Durán

1998). Some caves support single species, whereas others house mixed species

such as the Cucaracha Cave with its mixed populations of three species, numbering

700,000 individuals (Lugo et al. 2001).

One of the industrial world’s most successful and recognizable logos is Bacardi

Rum’s bat silhouette. When you fly or cruise to Puerto Rico, you can immediately

locate the Bacardi distillery in Cataño as a result of the highly visible bat-like outline of the visitors center (See app. 2, p. 372). Why use a bat for a logo? It is a very

simple story. When Bacardi was still located in Cuba where the company started,

bats were symbols of good luck, good fortune, and excellence. The garage where

the first alcohol still was set up had bats in it. When the time came for a distinctive

logo, the owner’s wife fondly remembered the bats and said that it would bring

luck and stand for an excellent product, thus the bat logo. 

For further reading see Diaz 1983; Emmons 1990; Findley 1985; Fleming and

Heithaus 1981; Gannon 1991; Gannon and Willig 1994, 1998; Hill and Smith 1988;

Kunz 1982; Richards 1996; Science News 1994; Starrett 1962; Tuttle 1995; U.S.

Department of the Interior 1985, 1998; Weaver 1994; and Willig and Gannon 1991.

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Figure 12—The red fig-eating bat, an endemic species to Puerto Rico. 

A. Puente Rolón
Additional information on bats can be obtained by contacting: Bat Defenders,

1101 14th Street, NW, Suite 1400, Washington , DC 20005; or Bat Conservation

International, P.O. Box 162603, Austin, TX 78716

Termites

Termites are a complex group of social insects. Most people associate termites with

damage to wooden structures, when in fact the majority of the species of termites

are not involved with these problems. Termites are highly beneficial to the natural

environment. Less than 10 percent of the species has been identified as pests.

Negative economic importance has masked the enormously important ecological

role termites play in the breakdown of vegetation in the landscape and in nature’s

food chains. All termites are herbivores and decomposers. They exhibit a variable

diet with some feeding on firm deadwood; others on decayed wood, and others on

grass, dung, and leaf litter; some cultivate fungal gardens. They, in turn, are eaten

by most predators around them such as amphibians, reptiles, birds, mammals, and a

variety of invertebrates. Most termite swarms are heavily predated. Ants may be

their largest predator. They also exhibit tremendous variation in social behavior,

physiology, and regulation. Interestingly, this ancient group of animals is linked to

our current greenhouse effect controversy because they generate considerable

amounts of methane (CH4). Methane is a greenhouse gas 20 times as effective at

trapping heat as carbon dioxide (CO2). Humans are altering environmental conditions and habitats in many areas of the world, making it possible for termite populations to expand, thus further increasing their methane production.

Termites are mostly tropical in their distribution. They exhibit many unique

relationships, including:

➢ Complex social behavior

➢ Polymorphism

➢ Symbiotic relationships

➢ Intricate nest construction

➢ Being consumers of vast quantities of wood and other forms of 

cellulose

➢ Being consumed by many predators in a complex food web

➢ Special associations with fungi and termitophiles

➢ Nitrogen fixation

Taxonomically, termites belong to the order Isoptera. There are over 2,000 

identified species of termites, grouped into six families. Five of the six families

possess symbiotic protozoans necessary for cellulose digestion. They differ from

other social insects such as bees, ants, and wasps in that they do not exhibit lower

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Guide To The Ecological Systems Of Puerto Rico
social groups, their castes contain both sexes, and their digestive system involves

protozoans or bacteria as the true digesters of cellulose, a condition known as

hemimetabolism.

For those species that build aboveground nests, the nest wall serves as protection and as a thermoregulator. Nests are usually quite striking, and anyone who 

has ever traveled to the tropics has probably observed them. They appear as large

mounds coming out of the soil or large ball-like structures positioned on limbs or

trunks of trees. In Puerto Rico, large brown mounds in trees dot the landscape.

When examined closely, each mound will have a series of covered trails called 

galleries leading from the colony to active deadwood feeding sites up to 30 meters

(98 feet) away. These are protective pathways used by workers in securing food for

the colony. Most feeding occurs at night, and termites use pheromone deposits for

direction. Termites have little protection against desiccation; thus they must reside

within the controlled environment of the nest. In the nest, temperature, humidity,

and CO2 are regulated. Relative humidity is generally in the range of 90 to 99 

percent, and the temperature is higher than the outside temperature.

There are a variety of other organisms associated with termite colonies.

Beetles, flies, fungi, and protozoans have developed highly interdependent associations. These organisms are called termitophiles. The relationships between host

and termitophile are species-specific. Some termite colonies have fungus gardens

in them. The fungus grows on the termites’ excrement and may contribute nutritionally to the colony or be a source of heat and humidity. The five families of 

termites that possess protozoans in their hind-gut have evolved a classic example of

endosymbiosis. It is mutualistic in that both the host termites and the endosymbiont

gain from the relationship. The protozoans supply the needed enzymes for cellulose

digestion, and the termites supply the cellulose. As mentioned earlier, not all termites possess protozoans as digester symbionts. The sixth and largest family use

bacteria in cellulose digestion. Seventy-five percent of all termites have evolved

this relationship with bacteria. As termites grow and molt, the essential digester

symbionts are lost, thus they must be reinfected. The reinfection occurs as a result

of the close feeding and cleaning relationships between nonmating individuals

within the colony; thus there is intergenerational and intercaste dependency in these

complex communities. In addition, large numbers of the microbial symbionts are

digested by the termites, providing an important source of protein to their diets.

Puerto Rico has 17 species of termites, four of which are economically important (Torres 1994). Two of those species are dry-wood feeders. The other two are

subterranean species and feed on a variety of cellulose substrates. The termite

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General Technical Report IITF-35
species you will commonly see as you explore Puerto Rico is Nasutitermes

costalis. It builds large arboreal nests on the trunks of trees such as the flamboyán,

on major tree branches, fenceposts, and other raised substrates. These nests are

very obvious because they are quite large and chocolate brown in color. This termite primarily harvests dead wood from tree branches. It will have a complex array

of tunnels that protect workers as they forage for cellulose sources. The tunnels are

also brown. The nest has to be located in an area where the termites have a dependable supply of ground water, otherwise the colony will fail. It is a dry-woodconsuming species, thus it causes considerable damage to houses, furniture, and

other wooden structures. Colonies can easily be destroyed by pesticide injection or

mechanical breakup. In one day, while driving through rural Puerto Rico, you will

likely see 20 or more of these termite mounds. This species has bacteria in its gut.

Some of the nests of Nasutitermes will measure close to a meter (3 feet) in

size. The nest material is referred to as cartón (fig. 13). The cartón nests are constructed by the workers and are composed of saliva, liquefied fecal materials, and

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Guide To The Ecological Systems Of Puerto Rico

Figure 13—A large Nasutitermes costalis (termite) nest (height

approximately 60 centimeters or 23 inches) at the base of a red

mangrove (Rhizophora mangle L.) near La Parguera.

G. Miller
soil. The cartón contains lignin, cellulose, and hemicellulose. Functioning nests

have been known to last 18 years or more (McMahan 1996). Termite colonies are

almost immortal in that they keep making new nests as food supplies are used up. 

One of the reasons most housing and business construction in Puerto Rico is 

of cement today is because of the threat from termite infestation. Only dense hardwoods like mahogany, which has highly lignified heartwood, resists termite infestation. Some farmers harvest termite nests and feed them to their chickens or hogs.

For further reading on termites, see Graham 1952 and Krishna and Weesner

1969.

Endangered Species

Although biological extinction is a natural evolutionary process, it has been accelerated by human actions in the environment. As humans modify the vast number 

of environmental settings throughout the world, species may become locally exterminated and then exterminated at the regional level, thus producing extinction of 

a species. In 1985, E.O. Wilson wrote the following:

The worst thing that can happen during the 1980’s is not energy depletion, 

economic collapse, limited nuclear war, or conquest by a totalitarian government. As terrible as these catastrophes would be for us, they can be 

repaired within a few generations. The one process ongoing in the 1980’s 

that will take millions of years to correct is the loss of genetic and species

diversity by the destruction of natural habitats. This is the folly that our 

descendants are least likely to forgive us.

What is driving habitat loss? Much of it is associated with maintenance of 

our current world population. Although birth rates are falling in some areas of the

world and some countries are experiencing negative growth, the big crunch is yet

to come because it will take another 50 years before the number of people and their

impact reaches its peak. Our current 6.3 billion humans will likely mushroom to

somewhere between 7.3 and 10.7 billion by 2050. As indicated by United Nations

projections, Puerto Rico may see an increase in its population in the next 25 years

although its current birth rate is falling and the population has not grown as 

predicted.

Another major reason for the loss of species relates to black market activities.

Many plants and animals are sold because they are beautiful, exotic, dangerous,

rare, or bizarre. The rarer an organism becomes, the higher its value in the black

market. Many plants and animals are also used in patented and folk medicines.

Unfortunately, many are perceived as aphrodisiacs putting enormous pressure on

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General Technical Report IITF-35
many rare species such as bears, big cats, and the rhinoceros. The sale of endangered species and their parts is second only to drugs in the international black 

market.

Historically, there has been no documented plant extinction in Puerto Rico. 

On the other hand, there have been animal extinctions, including frogs, birds, and

mammals. Today, the U.S. Fish and Wildlife Service and Puerto Rico’s Department

of Natural and Environmental Resources are tracking the status of 79 protected

species in Puerto Rico and the Virgin Islands. Thirty of the species are animals,

which include mammals (5), birds (11), reptiles (11), and amphibians (3). Table 12

has a complete list. Forty-nine species of plants are on the protected species list and

include trees and shrubs (33), ferns (8), cacti (2), orchids (2), and herbaceous

species (4). Table 13 has a complete plant list. Descriptions of these species and

their habitat requirements (boxes 7 and 8) and, in some cases, published recovery

plans, are available from the two lead management agencies mentioned above.

Most of Puerto Rico’s endangered species are found in karst habitat.

The primary reasons for species endangerment throughout the world are:

➢ Habitat destruction/alteration

➢ Introduction of alien species

➢ Commercial hunting and harvesting

➢ Pest and predator control

➢ Collection of plants and animals for human enjoyment, research, 

trade, and others

➢ Pollution

➢ Ecological/biological changes

All of these activities take place in Puerto Rico. Many people are unaware of 

the impact their activities have on species and their habitats; therefore, more education is needed at all age levels so this problem can be better understood and 

individuals can make the best decisions in terms of how they interact with the 

environment.

Puerto Rico is currently facing a major controversy involving endangered sea

turtle species and the proposed development of a series of four north coast hotel

and residential resort complexes in the Luquillo-Fajardo area covering 1300

hectares (3,200 acres). In March 2002, the U.S. Fish and Wildlife Service raised

major objections based on the danger of losing the most important sea turtle nesting beach on the island. In 2001, biologists counted 346 leather back turtle

(Dermochelys coriacea) nests. The areas in question also contain protected mangrove forests, habitats for the endangered brown pelicans (Pelecanus occidentalis),

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General Technical Report IITF-35

Scientific name

Amphibians (3):

a

Eleutherodactylus jasperi (HC) a

Peltrophryne lemur

a

Eleutherodactylus cooki

Reptiles (11):

c

Ameiva polops (HC) c dAnolis roosevelti (HC)

a

Caretta caretta

a

Chelonia mydas

a

Cyclura stejnegeri (HC) b

Dermochelys coriacea (HC) b

Epicrates inornatus

b

Epicrates monensis granti

a

Epicrates monensis monensis (HC) c

Eretmochelys imbricata (HC) c

Sphaerodactylus micropithecus (HC)

Birds (11): c

Accipiter striatus venator

c

Agelaius xanthomus (HC) a

Amazona vittata vittata

c

Buteo platypterus brunnescens

b

Caprimulgus noctitherus

c

Charadrius melodus

c

Columba inornata wetmorei c

Corvus leucognaphalus a

Falco peregrinus tundrius

c

Pelecanus occidentalis

a

Sterna dougallii

Mammals (5):

c

Trichechus manatus manatus

c

Physeter macrocephalus c

Megaptera novaeangliae

c

Balaenoptera physalus

c

Balaenoptera borealis

Common name (Spanish)

Amphibians:

a

Coquí dorado

a

Sapo concho

a

Guajón

Reptiles: 

c

Lagartijo de Santa Cruz

c dLagartijo gigante de Culebra a

Cabezón o Caguama

a

Peje blanco

a

Iguana de Mona

c

Tinglar

c

Boa puertorriqueña

c

Boa de Islas Vírgenes

a

Boa de Mona

c

Carey de concha

c

Salamanquita de monito

Birds:

c

Falcón de sierra

c

Mariquita

c

Cotorra puertorriqueña

c

Guaraguao de bosque

c

Guabairo

a

Playero melódico

c

Paloma sabanera

c

Cuervo pescueciblanco

a

Falcón peregrino

c

Pelícano pardo

a

Palometa

Mammals: 

c

Manatí antillano

c

Cachalote

c

Ballena jorobada

c

Ballena de aleta

c

Ballena sei

Common name (English)

Amphibians:

a

Golden coqui

a bPuerto Rican crested toad a

Puerto Rican rock frog

Reptiles:

c

St. Croix ground lizard c dCulebra giant anole

a bLoggerhead sea turtle b

Green sea turtle

a cMona ground iguana b cLeatherback sea turtle

b cPuerto Rican boa

b cVirgin Islands tree boa b cMona Island boa

b cHawksbill sea turtle

b cMonito gecko

Birds:

c

Sharp-shinned hawk

c

Yellow-shouldered blackbird

c

Puerto Rican parrot

c

Broad-winged hawk

c

Puerto Rican nightjar

b cPiping plover c

Puerto Rican plain pigeon

c

White-necked crow

c

Peregrine falcon

c

Brown pelican

c

Roseate tern

Mammals: 

b cAntillean manatee c

Sperm whale

c

Humpback whale

c

Finback or fin whale

c

Sei whale

Table 12—Animals in danger of extinction

a Species threatened.

b See appendix for sources of educational wall charts describing endangered West Indian manatee, Puerto Rican toad, 

marine sea turtles, and Puerto Rican boa.

c Species in danger of extinction.

d Probably extinct.
Trees and shrubs (33):

a

Auerodendron pauciflorum Alain a

Banara vanderbiltii Krug & Urban a

Buxus vahlii Baill. a

Callicarpa ampla Schauer a

Calyptranthes thomasiana O. Berg. b

Calyptronoma rivalis (O.F. Cook) Bailey a

Catesbaea melanocarpa Krug & Urban a

Chamaecrista glandulosa var. mirabilis (Pollard) Irwin & Barneby a

Cornutia obovata Urban a

Cordia bellonis Urban a

Crescentia portoricensis Britton a

Daphnopsis helleriana Urban a

Eugenia haematocarpa Alain a

Eugenia woodburyana Alain a

Goetzea elegans Wydler a

Ilex cookii Britton & Wilson a

Ilex sintenisii (Urban) Britton a

Juglans jamaicensis C. DC. a

Lyonia truncata Urban var. proctorii Judd a

Mitracarpus maxwelliae Britton & Wilson a

Mitracarpus polycladus Urban a

Myrica paganii Krug & Urban a

Ottoschulzia rhodoxylon (Urban) Urban a

Pleodendron macranthum (Baill.) V. Tieghem b

Schoepfia arenaria Urban & Britton a

Solanum drymophilum O.E. Schulz

b

Stahlia monosperma (Tul.) Urban a

Styrax portoricensis Krug & Urban a

Ternstroemia luquillensis Krug & Urban a

Ternstroemia subsessilis (Britton) Kobuski a

Trichilia triacantha Urban a

Vernonia proctorii L.E. Urbasch a

Zanthoxylum thomasianum (Krug & Urban) Krug & Urban

Ferns (8):

a

Adiantum vivesii Proctor a

Cyathea dryopteroides Maxon a

Elaphoglossum serpens Maxon & Morton ex Maxon a

Polystichum calderonense Proctor a

Tectaria estremerana Proctor & Evans a

Thelypteris inabonensis Proctor a

Thelypteris verecunda Proctor a

Thelypteris yaucoensis Proctor

Cactus (2)

b

Harrisia portoricensis Britton a

Leptocereus grantianus Britton

Trees and shrubs 

Palo de ramón

Capá rosa

Palma de manaca

Palo de nigua

Higuero de sierra

Uvillo

Matabuey

Nogal

Palo de rosa

Chupacallos

Erubia

Cóbana negra

Palo de jazmín

Palo colorado

Bariaco

St. Thomas prickly ash

Ferns 

Helecho arbóreo de bosque enano

Cactus 

Higo chumbo

Orchids 

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Guide To The Ecological Systems Of Puerto Rico

Table 13—Plants in danger of extinction 

Scientific name Common name (Spanish) 
Orchids (2):

a

Cranichis ricartii Ackerman a

Lepanthes eltoroensis Stimson

Herbs (4):

a

Aristida chaseae Hitchc. a

Aristida portoricensis Pilger b

Gesneria pauciflora Urban a

Peperomia wheeleri Britton a Species in danger of extinction.

b Species threatened.

Herbs 

Pelos del diablo

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General Technical Report IITF-35

Table 13—Plants in danger of extinction (continued)

Scientific name Common name (Spanish)

Puerto Rico plain pigeon (Columba inornata Wetmorei), and the Puerto Rico boa

(Epicrates inornatus). In addition, the National Marine Fisheries Service has indicated that the proposed projects are not in keeping with the Puerto Rico Coastal

Zone Management Program. This series of projects could involve a couple of kilometers (miles) of critical coastal habitat and would require a zoning change from

mangrove forest and conservation area to high-density development and use. The

change would likely result in the loss of critical nesting habitat and important fishery resource areas. There are an estimated 40 rare, threatened, or endangered

species present in this complex of wetlands and coastal fauna habitats in this vital

“northeastern ecological corridor.” Because much of the land is controlled by the

Puerto Rican Development Corporation, it could effectively be permanently protected. One of the most crucial issues facing Puerto Rico today is the chronic need

for setting aside presently owned lands and the continued need to purchase additional lands deemed critical habitats for the large number of endangered, threatened, and rare species on both federal and commonwealth lists. This is one of the

most important environmental decisions to be made in the first decade of this century. Hopefully, Puerto Rico’s leadership and natural resource management agencies will decide on behalf of protecting critical habitats and species, and protecting

vital water supplies in an area notoriously short of meeting its current water

demands. Unfortunately, in July 2003 a lawsuit filed by environmental groups and

local citizens against the Department of Natural and the Environmental Resources

claims that this lead environmental agency failed to inform other agencies about

the ecological significance of the lands in question prior to their consideration for

lease or sale. The case is under Superior Court review.

Prior to his death in May 2000, John Sawhill, head of the Nature Conservancy,

wrote the following poignant statement: “In the end our society will be defined not

only by what we create, but by what we refuse to destroy.”
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Guide To The Ecological Systems Of Puerto Rico

Box 7. Stahlia monosperma (Tul.) Urban (cobana negra)

Stahlia is a monospecific genus (only 

one species in it). This small tree was 

listed as an endangered species in 1990.

It, like so many other listed species, has

been greatly affected by the loss and 

modification of its habitat and the fact

that its wood had utility. It is typical of

dry coastal limestone woodlands, such 

as at Guánica and Cabo Rojo in southwestern Puerto Rico and on Vieques

Island. It was thought to be endemic to

Puerto Rico, but is now reported to be

present in a very restricted area in 

eastern Dominican Republic.

It can grow to 20 meters (65 feet) 

in height, but most individuals are smaller because the largest individuals in

the small populations had been previously cut. The leaves are compound,

alternately arranged, with 6 to 12 leaflets. Inflorescences are terminal racemes

10 to 15 centimeters (4 to 6 inches) long and the petals are light yellow.

Flowering occurs from February to June, with fruits maturing from June

through September. The fruit is a small, red to purple, fleshy legume about 5

centimeters (2 inches) long, with one seed. 

The wood of cobana negra is very hard, dense, durable, and termite resistant. The heartwood is dark brown, whereas the sapwood is light brown in

color. It had value as furniture wood, but today, because of its listed status and

the fact that so few large trees remain, it is no longer used for that purpose.

Historically, cobana negra was mainly a construction wood species. It is successfully being propagated at the tree nursery in the Cabo Rojo National

Wildlife Refuge and outplantings are being made there, since they are attempting to ecologically restore significant sections of the refuge by using native

species. Previously, most of the area had been converted to pasture or agricultural land. A variety of introduced forage species and exotic woody plants

have dominated the area in recent decades. Other groups concerned with

cobana’s status are working on developing seedling nurseries and establishing

new populations.

For more information about this species see Liogier 1997 and Little and

Wadsworth 1964.

The leaf, flower, and fruit of Stahlia

monosperma (Tul.) Urban (cobana negra)
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General Technical Report IITF-35

Box 8. Juglans jamaicensis C. DC. (Jamaican walnut) (Locally

known as nogal)

According to Manning (1979), 

there are 59 species in the genus

Juglans. They are distributed throughout the world including North, South,

and Central America, and the Greater

Antilles. Juglans jamaicensis is the

only native walnut found in the West

Indies. It is an extremely rare tree

found in moist mid-elevation mountain habitats in Puerto Rico. Its 

regional distribution includes the

neighboring islands of Hispaniola and

Cuba. Its rarity in large part is due to

its primary habitats being coincident

with areas of human habitation and 

deforestation associated with montane 

zone agriculture and grazing. In all likelihood, this species was already rare at

the turn of the last century owing to local cutting pressures and the establishment of coffee plantations.

Francis and Alemañy (1994) indicated that Jamaican walnut (locally known

as nogal) only occurred in three forests in Puerto Rico in 1928. By 1974 it was

highly restricted to one relict stand of just 14 individual trees. It is now listed

as a U.S. endangered species. It is also classed as an endangered species in the

Dominican Republic, but there its population is larger. Although the specific

epithet (jamaicensis) suggests that it is from the island of Jamaica, it is now

thought to be extinct there. Some question whether it ever occurred in Jamaica.

This species prefers cool, moist montane sites, on well-drained clay soils.

The one existing stand in Puerto Rico is located at an elevation of 975 meters

(3,200 feet). In other islands it has been associated with flood plains at lower

elevations. Today it is found in secondary forests and in Puerto Rico’s case,

the stand is in an old coffee plantation. In the Dominican Republic it can be

found in old agroecosystems.

The leaf, flower, and fruit structures of

Juglans jamaicensis C.D.C. (Jamaican 

walnut)
Box 8. continued

Jamaican walnut produces small green flowers in catkins, with both male

and female flowers on the same tree (monoecious). Flowering can occur from

February to April. By June, ripened, round walnuts are formed, which fall in

early summer. Trees can produce up to 100 large one-seeded fruits 4 to 5 centimeters (12 inches) in diameter. Today, fruit dispersal is largely by humans.

Walnuts native to the United States are frequently distributed by squirrels, 

but Puerto Rico has no equivalent animal, so it is likely that this species may

have always had a restricted range. Seeds produced in flood plains are likely 

vectored by water.

Tree growth can be rapid, and medium to large trees result with maximum

heights being up to 30 meters (98 feet). No trees in Puerto Rico are this large.

As is the case for other walnuts, leaves are large, odd pinnately compound,

and alternately arranged. There are 16 to 20 fine-toothed, lanceolate leaflets.

Small buttresses develop at the root/shoot interface. Jamaican walnut is thought

to be shade tolerant so it is likely to be a primary forest species should the

ecosystems it inhabits have a chance to fully recover.

The wood of walnuts is generally considered of high value because it has

been used extensively for the creation of some of the finest and most expensive furniture and specialty crafts. Walnut furniture is highly prized for its special dark brown color and graining. Many of these products are passed from

one generation to another and are a part of the thriving antique fine furniture

market. If properly cared for, these wood products can be useable for hundreds

of years. The good wood qualities and high value have caused this species to

disappear from much of its range. Unfortunately, Juglans jamaicensis populations are so small today that its wood is no longer available for commercial

use throughout its West Indian range. If it could be grown in large volumes,

this species would have great commercial value in today’s competitive wood

market. It is being propagated today in both Puerto Rico and Cuba.

This species has a variety of uses. It is valued as a nut food for humans

and wildlife. Its wood is used for fine furniture, craft production, and general

carpentry and interior finish wood. The juice from the fruit wall is used as a

fabric dye, and bark and leaf extracts are used for home medicines.

For more information on this species, see Francis and Alemañy 1994,

Little et al. 1974, and Manning 1960.

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Guide To The Ecological Systems Of Puerto Rico
There is no more important issue than that of protecting our planet’s biodiversity, that is, its genetic, species, and ecological richness. Everyone plays a role in

the destruction; therefore, everyone must play a role in the conservation and 

protection.

For further reading, see Delgado-Mendoza et al. 1990, Meffe and Carroll 1994,

and U.S. Department of the Interior 1997.

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Continue
Chapter 3: Terrestrial Ecosystems

Subtropical Forest Life Zones of Puerto Rico

At the time of discovery, most of Puerto Rico’s 890 000 hectares (2.2 million 

acres) of land was forested. By 1900, forest cover had been reduced to 189 000

hectares (467,000 acres) largely as a result of clearing for agriculture, timber harvest, and pasturage. By the late 1940s, deforestation was greater than 90 percent. In

the 1950s, forest recovery began, and by 1990, forest cover had grown to 287 000

hectares (709,000 acres) (Franco et al. 1997). Forests now cover 40 percent of

Puerto Rico. Older mature vegetation covers only 1 percent of the island, whereas

older successional vegetation covers 10 percent. The remaining forest cover is

young mixed-species stands. Today, the forests of Puerto Rico are very important

because they supply the habitat for thousands of species of plants and animals. In

addition, they are vital in helping to provide life support for nearly 4 million people. This is especially true for water supplies for municipalities, agriculture, and

industry. They are also becoming important as recreation destinations for a growing

urbanized population. The changes in forest dynamics intensively studied in Puerto

Rico may be useful in gauging changes that will be experienced in many tropical

islands throughout the world as the human population continues to expand. Insular

systems make interesting case studies for a variety of environmental changes produced by human activities. Puerto Rico’s forested ecosystems have been highly

altered in the last 200 years owing to introduction of various economically important plants such as sugarcane,1 coffee, bananas, tobacco, pineapples, and others.

Considerable forest clearing also took place for pasturage and charcoal production.

Today, forests and old agricultural lands are disappearing as a result of construction

of highways, transmission lines, ports, refineries, mines, powerplants, industrial

developments, and many other activities associated with extensive urbanization.

Trends toward urbanization and industrialization are producing an opportunity in

Puerto Rico to study what happens to large areas of a tropical island when released

from intensive agricultural use. Successional sequences are being documented to

understand natural recovery of forested ecosystems in areas massively degraded in

the past.

Ewel and Whitmore (1973) published a USDA Forest Service monograph,

Ecological Life Zones of Puerto Rico and the U.S. Virgin Islands. Much of what

follows in this section was initially described in that document. Their work was a

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Guide To The Ecological Systems Of Puerto Rico

1 See appendix 1 for Common and Latin names.
General Technical Report IITF-35

80

seminal document that pulled together our understanding of the life zones at that

time. Since then, considerable new research has added insight to the structure and

function of these forested zones. Much of the research has been carried out through

the auspices and cooperation of the USDA Forest Service’s International Institute

of Tropical Forestry in Río Piedras, Puerto Rico.

We now know that the forests of Puerto Rico are extremely diverse for a landmass the size of the island. The forests range from dry forests to rain forests, lowland forests to lower montane forests, saltwater to freshwater forested wetlands,

and forests on alluvial, karst, volcanic, and ultramaphic substrates. These forests

occur in stages of succession including those influenced by human activities, those

recovering from hurricanes or other natural disturbances, and those in mature

stages of development. More forest variation is added by topography, rainfall, soil

conditions, and aspect. Each of these categories of forest type intermix in such a

way that the actual number of forest types on the island is quite large, and there is

no systematic record of the full diversity of forest types. The most recent map of

conditions for forest growth in Puerto Rico contains 28 geoclimatic zones. This

new map is much finer in its site definition than the original descriptions at the life

zone level, which depict only climate.

Puerto Rico lies at approximately 18o N latitude in what Holdridge2 3 classified as the subtropical latitudinal region. This system of classification is for climatebased life zones and is presented in figure 14.

Holdridge’s theses are that:

➢ Mature, stable plant formations represent physiognomically discrete 

vegetation types that are easily recognized throughout the world.

➢ Vegetation and geographic boundaries correspond closely to climatic 

zones.

➢ Vegetation is determined largely by the interaction of temperature and 

rainfall.

Holdridge’s life zones for the world are arranged by latitudinal region, altitudinal belt, and humidity province. Each zone is defined by mean annual precipitation

and mean annual biotemperature. Biotemperature refers to all temperatures above

freezing, with all temperatures below freezing adjusted to 0° C. Also important are

available moisture and potential evapotranspiration. In general, rainfall ranges are

associated with the following forest types: 

2 Leslie Holdridge was the first scientist appointed at the USDA Forest Service Experiment 

Station in Río Piedras.

3 Figueroa Colón, J.C. 2001. Map for the geoclimatic zones of Puerto Rico. On file with: the

International Institute of Tropical Forestry, Río Piedras, Puerto Rico.
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Guide To The Ecological Systems Of Puerto Rico

Figure 14—

The Holdridge life zone system for classifying plant formations.
General Technical Report IITF-35

82

➢ 500 to 1000 millimeters (20 to 40 inches) - dry forest

➢ 1000 to 2000 millimeters (40 to 80 inches) - moist forest

➢ 2000 to 4000 millimeters (80 to 160 inches) - wet forest

➢ 4000 to 8000 millimeters (160 to 320 inches) - rain forest

According to the Holdridge system, Puerto Rico has six subtropical life zones 

ranging from dry through moist forest zones in the basal, or sea level belt. In the

wet and rain forest zones of the lower montane altitudinal belt, there are four forest

zones. Figure 15 shows the major forest life zones of Puerto Rico. 

The area occupied by each life zone is presented in table 14. The subtropical

moist forest is the largest life zone, covering more than 59 percent of Puerto Rico,

whereas the subtropical lower montane rain forest is the smallest life zone.

Unfortunately, most forests of the subtropical moist forest zone have been

destroyed.

The forest zones described in this section can all be seen in the 14 commonwealth forests and nature reserves located throughout Puerto Rico. See the location

map and short descriptions in the “Commonwealth Forests and Nature Reserves”

section that follows.

Figure 15—Ecological life zones of Puerto Rico.
The large diversity of ecosystem types in such a small island means that no

ecosystem type covers a large area. The island is a mosaic of diverse ecosystem

types. Because of Puerto Rico’s high population density and intense human development activities, these ecosystems are highly fragmented. The steep topography

and abundant rainfall results in a high degree of coupling between ecosystems. For

example, when it rains in the mountains, rivers swell rapidly and quickly discharge

nutrients and sediments on coastal ecosystems. Within hours, events in the mountains impact coastal ecosystems. This degree of connectivity, coupled with the

small size of many types of ecosystems, has enormous implications for their management and conservation. Tropical ecosystems of Puerto Rico are ecologically

resistant and resilient to numerous environmental disturbances, but are very 

vulnerable to improper human activities.

The Subtropical Dry Forest

For the last 30 years there has been a continuous debate throughout scientific, 

political, and economic circles regarding the devastating loss of tropical rain forests

and their diverse assemblage of species. By comparison, very little concern has

been expressed until recently about the loss of dry forests. One reason was because

by the 1970s most of the dry forests of the world had already been severely altered.

Some estimates indicate that up to 42 percent of forests in the tropics were originally dry forests. In addition, possibly 60 percent of current scrub forest and savanna

may have been dry forests prior to human alterations. In some areas today, dry

forests are only historical remnants, whereas many other areas have only 1 to 5 

percent left. There are still large functional dry forests in Africa and tropical islands

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Guide To The Ecological Systems Of Puerto Rico

Table 14—Area (square kilometer) occupied by each life zonea in Puerto Rico 

Lower Lower

Percentage Dry Moist Wet Rain montane montane Total

Island of total area forest forest forest forest wet forest rain forest area

Square Kilometer

Puerto Rico 97.46 1,216.4 5,326.1 2,124.8 13.2 109.1 12.3 8,801.9

Vieques 1.53 93.1 44.8 0 0 0 0 137.9

Mona 0.63 56.1 b

0 0 0 0 0 56.1

Culebra 0.36 32.7 0 0 0 0 0 32.7

Desecheo 0.02 1.6 0 0 0 0 0 1.6

Total 100.00 1,399.9 5,370.9 2,124.8 13.2 109.1 12.3 9,030.2

Percentage of total area 15.50 59.48 23.53 0.15 1.21 0.13 100

in life zone

a All life zones are tropical.

b 0 entries in the table indicate the absence of the life zone on that particular island.

Source: Modified from Ewel and Whitmore 1973.
General Technical Report IITF-35

84

where they cover 70 to 80 percent of lands that are still forested. In Central

America, of the land still forested, 50 percent may be covered in dry forest, and

South America has an estimated 22 percent in dry forest cover (Murphy and Lugo

1986).

Dryer conditions are generally much preferred by humans to the very wet

humid parts of the tropics, and in many dry forest zones, large human populations

have been supported for millennia. It is in such places that anthropologists theorize

the transition to an agriculture-based human society may have taken place.

Dry forests can occur in areas with roughly an even split of 6 months wet and 6

months dry. They also occur in other wet/dry ratios of 4:2 and 5:1. This is thought

to be one of the reasons why dry forest zones exhibit high species diversity, that is,

there may be two groups of plants and animals adapted to the different water and

vegetation regimes present. The conditions in dry forest zones are generally very

different from the wet zones in the following ways:

➢ Lower rainfall that may be erratic

➢ High air and soil surface temperatures

➢ Low humidity

➢ Drying winds

➢ Extensive amounts of sun

The dry zone is the driest of the six life zones in Puerto Rico (fig. 15). It covers

sizable areas in southwestern Puerto Rico and Vieques, plus all of Mona Island,

Culebra, and Desecheo Islands. Mean annual rainfall ranges from a minimum of

about 600 millimeters (24 inches) to a maximum of 1100 millimeters (43 inches).

The vegetation of this life zone tends to form a complete ground cover and is

mostly semideciduous on most soils. At the tops of ridges, the forest will be more

deciduous, and in valley bottoms, it will be mostly evergreen. Palms are usually

absent from the canopy, leaves are often small and succulent or coriaceous, and

species with thorns and spines are common. Tree heights do not usually exceed 15

meters (49 feet) and crowns are typically broad, spreading, and flattened, with

sparse foliage. Fire is common on the better soils in many parts of the world, where

the successional vegetation includes many grasses, and large amounts of organic

debris accumulates on the soil surface during the dry season. Fire is not a natural

factor in Puerto Rico, but is now being used in Puerto Rico as a control for alien

species along the roads in the Guánica Commonwealth Forest. Coppicing is a common means of regeneration of many of the woody species found in this life zone.

Successional forests, therefore, often consist of an almost-impenetrable maze of

tangled, close-growing, small stems. 
A dry forest is an excellent habitat in which to observe a variety of special

adaptations of both plants and animals. Plant adaptations to observe are:

➢ Water conservation (hairs, spines, folded leaves, dropped leaves)

➢ Succulents (plants that can store water, for example, cacti)

➢ Cladophylls (plants that use green stems for photosynthesis)

➢ Ephemerals (plants that complete their life cycle rapidly)

➢ Deciduousness (leaf drop in the driest period[s])

➢ Phreatophytes (deep roots, may penetrate to a ground-water source)

➢ Vertical orientation of leaves (to avoid direct rays of the sun)

➢ Microphylly (small leaves)

➢ Heat control (spines and stem design)

➢ Stomata that open at night

➢ Convergent evolution (cacti as opposed to euphorbs, look alike but are

from different parts of the world)

When compared to a wet forest, the structural traits of a dry forest will also 

vary where the following can be observed:

➢ Smaller stature (50 percent or less)

➢ May be floristically less complex (although dry forests can be species 

rich too; in fact, some dry forest zones may rival rain forests in diversity)

➢ Fewer layers to the forest

➢ Few trees common to the wet forest

➢ More abundant understory vegetation

➢ Higher percentage of the plant’s total biomass in roots

➢ Annual diameter growth of stems is less than in wet forests

As indicated earlier, the dry forest life zone has historically been the preferred 

area for human settlement in many tropical countries. The pressure to alter these

habitats has been ever increasing owing to:

➢ Agriculture

➢ Fire (prescribed and natural)

➢ Introduced species (goats, cattle, horses, pigs, and others)

➢ Firewood collection

➢ Increased human population growth and its attendant need for housing,

transport corridors, businesses, use of available surface, and ground 

water supplies

One of the premier examples of a Neotropical subtropical dry forest ecosystem 

is in the Caribbean on the south coast of Puerto Rico near the town of Guánica (see

app. 2). Fortunately, its unique qualities were recognized early on and it was set

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Guide To The Ecological Systems Of Puerto Rico
General Technical Report IITF-35

aside as a commonwealth forest in 1917. It was still used locally for coppice wood

harvesting, charcoal production, grazing, and so forth, until the early 1960s. It was

also the site of an introduced West Indian mahogany plantation, which is still there

and is being monitored to date. The Guánica Forest has received much better protection since the mid 1960s, and today it is a prime example of a Caribbean dry

forest, with full protection by the Puerto Rican government. In 1981, the 4000-

hectare (10,000-acre) forest was recognized by the United Nations for its special

habitat qualities and was declared an International Biosphere Reserve. Today, there

is a full-time reserve director and support staff that helps to monitor, promote

research, and actively educate the citizens about the unique features typical of dry

forest ecosystems. Recently, it added a marine sanctuary section under its control,

as it borders the Caribbean Sea. The Guánica reserve now includes mangrove

swamps, turtle grass beds, and coral reefs. This makes it one of the most unique

management schemes in the Neotropics, where terrestrial and marine ecosystems

are married together for management purposes, from the top of the watershed to the

sea. This reserve has more than 700 plant species, 16 of which are reported to be

endemic. It has more bird species than any other island forest.

Why is it so dry in the Guánica Forest when just a few miles away to the north

some mountainous areas may receive more than 5000 millimeters (200 inches) of

rain? The answer is relatively simple. The Cordillera Central Mountains that run

east-west through the middle of Puerto Rico produce an orographic rain shadow.

The prevailing trade winds bring moisture-laden clouds to the north side of the

island and, as they rise in altitude, more rain falls on the north side of the island. As

the clouds pass over to the south side, little water falls as rain, thus creating a rain

shadow with the driest section of the island situated in the area near the Cabo Rojo

lighthouse on the southwest coast. Figure 16 illustrates the differences in rainfall

distribution in the wet versus dry zones in Puerto Rico. To visit sites at the two

extremes of this gradient see app. 2.

Guánica’s driest period is December to April when nearly 50 percent of the

trees drop their leaves. For this reason, this forest is often called a deciduous 

forest. New leaves and flowers generally reappear from August to November.

Temperatures fluctuate little at Guánica, with daily temperatures averaging 25 oC

(79 oF). Guánica is in a windward area in that winds frequently come off the

Caribbean Sea in this low topographic system and may create a drying effect. Dry

forests in Puerto Rico extend inland up to 20 kilometers (12 miles). Water deficits

may occur up to 10 months of the year. Guánica has a variety of succulent plants

that exhibit special adaptations for coping in a heat/water stressed environment.

Plants to look for are:

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Guide To The Ecological Systems Of Puerto Rico

Figure 16—An idealized transect through a Caribbean island in the Lesser Antilles.
General Technical Report IITF-35

➢ Opuntia dillenii (Ker-Gawl) Haw. (prickley pear cactus)

➢ Opuntia rubescens Salm-Dyck ex. DC (tree opuntia cactus)

➢ Cephalocereus royenii (L.) Byles & Rowley (large pipe cactus)

➢ Lemaireocereus hystrix (Haw.) Britton & Rose (pipe organ cactus)

➢ Melocactus intortus (Miller) Urban (Turk’s cap cactus)

➢ Euphorbia lactea Haw. (African cactus—it is really a euphorb in the family

Euphorbiaceae)

The Guánica Forest is not structurally tall, but quite dense (fig. 17). There may

be 12,000 tree stems per hectare. Most have relatively narrow diameters at breast

height (d.b.h.). Many trees are either natural or coppice regrowth from past use for

grazing, household wood collection, or charcoal pits. Species diversity of trees and

shrubs in Guánica is comparable to that found in the rain forest in the Caribbean

National Forest. Figure 18 illustrates species zonation in the Guánica Forest.

Some of the low alluvial areas on the south coast of Puerto Rico contain saline

soils, such as the Santa Isabel series, and vegetation on these sites is dominated by

Prosopis juliflora (Sw.) DC. (mesquite), an introduced tree. Parkinsonia aculeata

L. (Jerusalem thorn) is another alien leguminous tree that often forms nearly pure

stands on coastal alluvial soils.

Interesting dry forest plants to look for are:

➢ Acacia farnesiana (L.) Willd. (sweet acacia)

➢ Bursera simaruba (L.) Sarg. (Gumbo limbo) (box 9)

➢ Calotropis procera (Aiton) W.T. Aiton (African milkweed tree)

➢ Comocladia dodonaea (L.) Urban (chicharrón “poison ivy”—very 

common in Guánica forest)

➢ Guaiacum officinale L. (lignum vitae)

➢ Parkinsonia aculeata L. (Jerusalem thorn)

➢ Plumeria rubra L. (frangipani) (box 10)

➢ Prosopis juliflora (Sw.) DC. (mesquite)

There are many more bird species present in the Guánica Forest than in the 

montane rain forests (31 versus 20 species per 1,000 individuals). There is almost

four times the bird density with 190 in Guánica versus 57 per linear kilometer (0.6

mile) in the rain forest. In discussing the greater number of insect-eating birds at

Guánica, Kepler and Kepler (1970) pointed out that the wetter Luquillo Forest had

well-developed lizard and frog populations, which might be performing the same

function in the Luquillo Forest as insectivorous birds do in the drier Guánica

Forest. In looking at the broader question of why the structurally simple dry forest

88
should have more birds, numerically and taxonomically, than the complex wetter

forest, they state:

The answer may well lie in the greater relative ability of xeric land birds 

from potential source areas to colonize oceanic islands, the larger number 

of xeric, compared to mesic, islands that could serve as stepping stones for 

dispersion in the Caribbean, and the proximity of the xeric forest to island

coasts where potential propagules would first land.

Animals will also exhibit interesting adaptations to dry forest conditions. 

Consider the following:

➢ High percentage of nocturnals

➢ Many-scaled species that prevent desiccation

➢ Water sources from prey and vegetation

➢ Hibernation

➢ Burrowing or use of natural grottos (e.g., Puerto Rican crested toad,

Peltophryne lemur)

➢ Low perspiration

➢ Pallid colors

➢ Ground/shrub nesters

Agriculture in the subtropical dry forest life zone is, at best, a marginal business, except under irrigation. The amounts of water that must be added to maintain

crops and pastures in Puerto Rico are low, compared with irrigation demands in

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Guide To The Ecological Systems Of Puerto Rico

Figure 17—A general view of the Guánica Dry Forest in the south coast of Puerto Rico. 

G. Miller
General Technical Report IITF-35

90

Figure 18—Zonation of species in a dry forest such as Guánica.
Box 9. Bursera simaruba L. Sarg. (gumbo limbo) (Locally known as 

Almácigo)

This tree is typical of dry habitats. It has

a thin copper-colored bark resembling the

skin color of American aboriginals. It is

somewhat unique in that under the coppery 

bark there is a chlorophyll-bearing layer that 

permits its bark to photosynthesize when it 

is leafless, which can be up to 6 months of 

the year. This chlorenchyma layer can be 

exposed by scraping the paper thin outer 

layer with your fingernail or small pocketknife. Also notable is that it grows throughout the Caribbean Basin and Florida, and 

in each country or area it has a different 

common name. There are more than 50 

local common names for this tree.

This medium-sized tree is native to Puerto Rico and the Virgin Islands 

and can achieve a height of 12.2 meters (40 feet) in well-drained alluvial valleys. It has a wide crown with crooked branches and thin foliage. The leaves

are odd pinnately compound, with 3 to 7 ovate leaflets with oblique bases. Its

slender flowers are white to yellow-green, arranged in a panicle. Most trees

are male or female (dioecious), although occasionally bisexual. Flower parts

are in fives, with a three-celled ovary that produces a diamond-shaped drupelike fruit that eventually splits into three parts. Flowering and fruiting usually

occurs from March to June prior to renewal of leaf growth.

The tree produces an aromatic sap with an odor like turpentine when the

bark is cut. The odor is also present in the leaves and fruit. On some islands,

its common name is turpentine tree. The wood is both light in color and density, without growth rings, and is susceptible to insect attack, especially by drywood termites. The wood is used for low-end products such as toothpicks,

boxes, matches, charcoal, plywood, particle board, and basic construction. The

resins are used in glue, varnish, incense, and folk medicines. The trees are also

used as living fence posts, and are easily propagated via cuttings. It is salt

spray tolerant. Because the coppery bark is attractive, it is used as a landscape

plant, especially in dry zones. This tree is common throughout the dry zones

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Guide To The Ecological Systems Of Puerto Rico

The leaf, flower, and fruit of Brusera

simaruba (L.) sarg. (gumbo limbo)
General Technical Report IITF-35

Box 9. continued

of the south coast of Puerto Rico and is readily found in the Guánica Forest.

These trees exhibit pronounced trunk swell as a water storage mechanism for

the dry season. They also produce a deep tap root that can absorb ground

water. It does well in strong winds as it will lose its leaves, thus preventing

windthrow. The largest gumbo limbo is located in Coamo and has a height of

14 meters (46 feet), a crown spread of 12 meters (39.2 feet), and a circumference of 2 meters (6.5 feet).

For more information on this species, see Francis 1990, Little and

Wadsworth 1964, and Schubert 1979.

92

Box 10. Plumeria rubra L. (frangipani) 

As you move across Puerto Rico 

you will see this small tree in many 

people’s yards, and if you visit the 

Guánica Forest, you will see it in the 

wild. It is frequently planted because 

of its delicate and wonderfully 

scented flowers.

Frangipani is a small tree, rarely 

taller than 7.6 meters (25 feet). Its 

crown is open, with a few spreading 

branches that have leaves clustered at 

their ends. Its bark is smooth and gray. 

In most areas it is evergreen, but in dry 

areas it may be deciduous. The leaves are entire, elliptic, leathery-shiny green,

and densely alternate in arrangement. The bottom leaf surface is hairy. Its most

distinguishing feature is its waxy flowers, which are 5 to 7 centimeters (2 to 3

inches) across, with an overlapping set of lobes. The terminal flowers produce

a flat-topped cyme inflorescence. The stamens, petals, and sepals are in fives,

with two pistils. The fruits that result are leathery brown follicles that open on

one side releasing many small winged seeds. Flowering and fruiting goes on

throughout the year in Puerto Rico. In dry areas, the tree may flower when

there are no leaves present. Flower color is variable from red, to rose, and white

to yellow in cultivated varieties. There is another white-flowered species, 

The leaf and flower of Plumeria rubra L.

(frangipani)
Box 10. continue

P. alba L., which has lance-shaped leaves, with dense hair on the bottom 

surface. It is very common in the southern and western parts of Puerto Rico.

Frangipani flowers do not wilt rapidly, and as a result, they are often picked

for displays.

This tree’s main use is as an ornamental in gardens, parks, and cemeteries.

It flowers throughout the year and produces large clusters of fragrant flowers

that persist. It produces only a minimum of leaf debris. It does not grow into a

large tree, thus it is not likely to produce residential damage in tropical storms.

Frangipani gets its name from the French word frangipanier, which means

coagulated milk, descriptive of the white latex that exudes from its branches or

petioles when cut or damaged. It may be poisonous and is said to be used in

folk medicines.

Frangipani grows easily from cuttings and can do well in very dry, to

drained moist conditions. It is salt tolerant and can be found near beaches. It

has been distributed throughout the tropical world, but was originally derived

from Jamaica in the West Indies. Its life expectancy is about 30 years.

For more information on this species, see Little and Wadsworth 1964 and

Schubert 1979.

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Guide To The Ecological Systems Of Puerto Rico

many drier parts of the world. However, the better soils in this life zone are already

under cultivation. Potential evapotranspiration is greater than rainfall in the subtropical dry forest life zone, so the repeated use of irrigation water can sometimes

result in salt accumulation in the upper soil horizons. In the Lajas Valley of southwest Puerto Rico, for example, use of ground water for irrigation resulted in the

loss of agricultural productivity on some soils, until the mid 1950s when water

from another area was made available for irrigation.

Goats are pastured on the poorer soils, but to a much lesser extent than in years

past. Charcoal production, a common land use process in many tropical environments, was once common in this life zone in Puerto Rico, but this practice is now

almost extinct in Puerto Rico. The Guánica Forest, which has been protected from

charcoal wood cutting, goat grazing, and subsistence farming for more than 50

years, is perhaps the best example anywhere in the world of natural vegetation in 

a subtropical dry forest. Commercial forestry has little prospect in this life zone,

except in the limited production of exceedingly durable fenceposts and a few highquality specialty woods such as Swietenia mahagoni (L.) Jacq. (West Indies

mahogany) (fig. 19).
General Technical Report IITF-35

94

Figure 19—West Indian mahogany plantation in Puerto Rico.

Mangrove ecosystems may be present along the coast in dry forest zones. For

further information, see the mangrove ecosystem section later in this document.

The Subtropical Moist Forest

This life zone in Puerto Rico covers more area than any of the other five life zones.

It accounts for almost 5500 square kilometers (3,418 square miles), or 59 percent

of the total. It is delineated by a mean annual rainfall of 1000 to 1100 millimeters

(39 to 43 inches), that ranges to about 2000 to 2200 millimeters (78 to 86 inches)

and a mean biotemperature between about 18 and 24 oC (64 to 75 oF).

Most of the subtropical moist forest zone in Puerto Rico has been deforested at

one time or another owing to numerous human activities, but primarily because the

climatic conditions defining its boundaries also make good conditions for growing

a wide variety of crops. With the exception of the regions of serpentine- and limestone-derived soils, most of the land in this life zone remains in some form of 

nonforest use. A sizeable tract of cutover forest in the subtropical moist forest is in

G. Miller
the Caribbean National Forest (Luquillo Experimental Forest). This and other scattered remnants of this zonal association are characterized by trees up to 20 meters

(66 feet) tall, with rounded crowns, like those of the mango tree. Many of the

woody species are deciduous during the dry season, and epiphytes are common but

seldom completely cover branches and trunks. Grass-covered pastures form one of

the dominant landscape uses in the subtropical moist forest zone in Puerto Rico

today. Figure 20 illustrates the many forest types and land covers present in Puerto

Rico today (Helmer et al. 2002).

Karst—

The moist karst limestone hill region of northern Puerto Rico produces an interesting association in the subtropical moist forest zone. Puerto Rico’s karst region was

formed late in its geological history. After the mountains had formed, there was a

secondary island sinking. The adjacent shallow seas, with abundant sea life associated with coral reef formation in the Oligocene and Miocene periods, formed the

present coastal plain area from the Loíza area west to Mayagüez.

Numerous areas of the world exhibit karst topography. Puerto Rico has an

extensive karst belt on the north coast extending from Loíza (east of San Juan) to

the northwest coast (see app. 2). It extends south into the foothills of the Cordillera

Central Mountains for 25 kilometers (15 miles). Karst is also present on the south

coast, but more fragmented than and not as extensive as on the north coast. Karst

covers more than 27 percent of the island (Lugo et al. 2001). Karst regions are

characterized by the presence of rocky ground, caves, sinkholes, and underground

rivers. Puerto Rico has an incredible network of rivers, streams, and creeks (fig.

21). Only in the karst region are surface rivers absent. There, the drainage is

through underground rivers and aquifers that yield over 100 million gallons of

freshwater to the ocean each day. One of the largest underground sections of river

in the world is the Río Encantado found in the karst region of Puerto Rico. The

river runs 16 kilometers (9.6 miles) underground. Rivers in Puerto Rico appear

small to the casual observer. However, after heavy rains, all recipient rivers 

swell to enormous proportions and flood most of the coastal zone of the island.

Instantaneous discharges of thousands of cubic feet or cubic meters per second 

are common during hurricane-induced floods. Floods can be instantaneous given

the island’s steep topography and the steep gradients of rivers. In 1998 during

Hurricane Georges, the Río Camuy River, which runs underground through the 

Río Camuy Park, rose 45.7 meters (150 feet) and flooded the major room of the

Río Camuy Caves. It was the greatest increase ever recorded for a river in Puerto

Rico. The previous record increase inside the cave was 24.4 meters (80 feet). 

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Guide To The Ecological Systems Of Puerto Rico
General Technical Report IITF-35

96

Figure 20—Forest sites and land uses of Puerto Rico.
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Guide To The Ecological Systems Of Puerto Rico

Figure 21—

The rivers of Puerto Rico. Each small line of this map represents a river.
General Technical Report IITF-35

In many karst areas, haystack-shaped hills are present (fig. 22). The landscape

is often called egg-carton topography. This unusual landform results from the effect

of water running over and through massive deposits of soluble limestone or calcium carbonate (CaCO3). For karst to develop, there must be a soluble base rock

near the surface. There also has to be a humid climate for maximum development,

with moderate to heavy rainfall to produce the ground water circulation and the

dissolution of the CaCO3. The naturally acid rain then percolates through the calcium carbonate via cracks and carries it away in solution. As the cracks enlarge over

long periods, they can become small single caves, cave systems, or underground

stream systems. Most of the cave areas of the world are in karst regions. Puerto

Rico has thousands of caves. Often the roof of one or more caves will subside and

this can produce natural bridges or, more likely, sinkholes. Puerto Rico’s karst

region is an area of rolling rough surface with numerous haystack hills, sinkholes,

and caves of various sizes. Some haystack hills are well over 100 meters (328 feet)

high, whereas sinkholes may be hundreds of meters (hundreds of feet) deep and

broad. As will be mentioned later, the Arecibo Ionospheric Observatory is built

over a giant sinkhole (see app. 2). Some of the streams that originated on the surface periodically disappear, only to resurface kilometers (miles) later as they make

their way to the coast.

The haystack hill region is one of the best displays of this formation in the

world. Haystacks, called mogotes in Puerto Rico, are not pure limestone. Mogotes

have sands and clays eroded from the Cordillera Central range mixed in. Much of

the CaCO3 was dissolved and ran off in the rainwater leaving the clays and sands

behind. There is a difference in the degree of slope on the haystacks, with the western sides being steeper and the east and north sides more gently sloping. Why the

difference? The reason is that the east sides are warmer and dryer, whereas the west

and north sides are cooler and moister. This produces more solution and movement

on the west sides. The haystack hills have an external limestone cover that results

from a dissolution → evaporation → precipitation cycle much like what goes on in

the formation of stalactites. This CaCO3 precipitate is much harder than the original limestone and thus the mogotes keep their shape. The limestone precipitate may

be up to 3.5 meters (12 feet) thick. This same process is involved in the formation

of large deposits of beach rock at the ocean’s edge.

Haystack hills are also ecologically interesting. They are excellent examples of

the changes in microhabitat conditions that take place as you move up in altitude

and soil and moisture conditions are altered. In the wetter part of the year they are

dark green, whereas in the dry season they appear gray-green and deciduous. Many

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Guide To The Ecological Systems Of Puerto Rico

A

B

Figure 22—Aerial (a) and ground (b) views of limestone hills on the north coast near Arecibo, Puerto

Rico. 

L. Miranda Castro
General Technical Report IITF-35

of the mogotes are 91 to 122 meters (300 to 400 feet) tall and exhibit quite distinctive zonation of physical conditions, morphological variation, and species composition as you move from top to bottom. For example, the tops of the haystack hills

are considerably dryer than the middle and lower sections, so much so that the top

may be covered by deciduous vegetation, the middle by semievergreen, and the

base by evergreen vegetation (fig. 23). Keep in mind that the rainfall is not any 

different (average 192 centimeters [77 inches] per year). Species composition,

physical structure, morphology and density all change from top to bottom. Canopy

height of trees typically ranges from 4.5 to 7.6 meters (15 to 25 feet) at the ridgetop, whereas in the middle slope it ranges from 12 to 18 meters (40 to 60 feet), and

in the valley at the base of the hill 15 to 27 meters (50 to 90 feet). The d.b.h. will

vary from 10 cm (4 inches) on top, to 15 cm (6 inches) in mid elevations, to 25 cm

(10 inches) at the base of the haystack. Leaf morphology will also vary according

to location.

As can be seen in table 15, all physical and vegetation features vary from top

to bottom of a haystack hill. At the ridgetop it is more exposed with little soil, but

with a good duff layer. It is rocky and there is less soil moisture. Vegetation is

smaller in height and diameter, and plants express morphological features typical 

100

Figure 23—Dry woodlands on the tops of mogotes and mesophytic forest at the base. 

L. Miranda Castro
Table 15—Haystack hill zonation and plant features

Ridge Slope Valley

Physical or 69 to 122 meters 30 to 69 meters < 30 meters

vegetation features (225 to 400 feet) (100 to 225 feet) (< 100 feet)

Soil conditions Dry litter in rocky Litter layer Good soil profile and moisture

crevices

Available moisture Low Mid High

Canopy height 4.6 to 7.6 meters 12 to 18 meters 15 to 27 meters

(15 to 25 feet) (40 to 60 feet) (50 to 90 feet)

Tree diameter at 10 centimeters 15 centimeters 25 centimeters

breast height (4 inches) (6 inches) (10 inches)

Leaf size 7.6 centimeters 15 centimeters > 15 centimeters

(3 inches and (6 inches) (> 6 inches)

smaller)

Leaf characteristics Small, sclerophyllous, Leathery, mesophyllous, Larger, leathery, 

often spiny, thick moderately thick membranous and thinner

Leaf apex shape Rounded-obtuse Acute-obtuse Acute-acuminate

Shrub height 1 meter 1.8 meters 2.74 meters

(3 feet) (6 feet) (9 feet)

Shrub species Moderate High Lower

Vine species High Low Moderate

Vine size Small twiners Mixed Larger

Plant density

(800 m2 plot)

Trees 200 180 86

Shrubs 354 460 256

Lianas 126 42 96

Herb presence Few Very low High

Epiphyte presence High Few Very low

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Guide To The Ecological Systems Of Puerto Rico

of warmer and dryer conditions. These include smaller leaves, which are sclerophyllous, many that are spiny or with dense pubescence. The tree vegetation at the

base of the mogote is much taller, with larger d.b.h., larger leaves, not sclerophyllic, and less thick. Most do not express the dense pubescence or presence of spines.

Soils at the hill’s base are deep and moist; in fact, in valley depressions it may be

peaty, with ferns and mosses.

Haystack hills on an area basis are very species diverse. According to Lugo et

al. (2001), the karst region harbors more than 1,300 species of plants and animals,

including 30 federally listed threatened and endangered species. More than 75

species of Neotropical migratory birds use karst for wintering habitats. Reports

indicate that large hills may have 500 to 800 species, whereas small hills could

have 200 to 500 species. Large hills can have up to 200 tree species present, whereas small hills may have 50. Each haystack hill differs in species composition, but in

general the structure is similar. In general, the larger/higher the hill, the higher the
General Technical Report IITF-35

species presence. Many species exhibit an altitude/edaphic preference and cluster

out in each zone (fig. 24).

Puerto Rico has two common plant species that produce skin irritations similar

to that caused by poison ivy, a plant species commonly found in the United States.

Both species are present on haystack hills. Comocladia glabra (J.A. Shultes)

Spreng. prefers moist habitats and can be found in the lower elevation of a hill or

nearby sinkholes. Comocladia dodonaea (L.) Urban prefers dry areas and will be

found in the upper elevation of a haystack hill. Both species are shrubs but can

become tree-like. They produce pinnately compound leaves that have spiny margins. The leaflets of Comocladia glabra (Shultes) Spreng. (carrasco) are larger

than those of C. dodonaea (L.) Urban. Comocladia glabra is more common in the

moist karst area and other moist forest areas, whereas C. dodonaea is more common in the dry areas of the south coast. Detailed descriptions of each species were

presented earlier.

Some haystack hills have the very tall and thin endemic palm Gaussia attenuata (O.F. Cook) Beccari (youmy palm). They stand out visually because of their

height. Animals typical of these areas include birds, lizards, frogs, snails, scorpions,

whip scorpions, and millipedes. There are 74 native fish and 25 fish species introduced to the waters of the north karst region. Nineteen caves have been investigated for their invertebrate faunas, and 151 species have been identified, many of

which are endemic.

Serpentine—

Serpentine-derived soil (Nipe and Rosario series) is a second edaphic condition 

that results in an interesting plant association in the subtropical moist forest 

zone in southwestern Puerto Rico (a good example can be seen in the Susúa

Commonwealth Forest). This soil supports unique vegetation, which contains a

number of endemics, but does not support any significant agriculture or commercial forestry. The trees are slender, open-crowned, and usually less than 12 meters

(39 feet) tall. The forest floor is open, for the excessively drained soil supports 

little herbaceous growth. Most of the species are sclerophyllous, and the vegetation

is almost completely evergreen. Tschirley et al. (1970) found 105 species of woody

plants larger than 2.5 centimeters (1 inch) d.b.h. on 0.9 hectare (2.2 acres) in this

association, compared to the 85 species on 1.4 hectares (3.5 acres) in the wetter,

more luxuriant Luquillo Forest. It is also an area rich in orchids. This surprising

richness of woody flora on the serpentine soils contradicts most current ecological

literature. 

102
103

Guide To The Ecological Systems Of Puerto Rico

Figure 24—A profile view of a moist coastal and limestone forest.
General Technical Report IITF-35

Mangroves—

Mangroves are found along the coast in the subtropical moist forest life zone where

they appear to grow taller than in the subtropical dry forest life zone (fig. 25). Just

inland from the mangrove forests are alluvial soils where the ground water may be

slightly brackish. Most of these soils were cleared long ago for agriculture, but

they probably supported impressive forests at one time. Gleason and Cook (1926)

described a stand of Pterocarpus officinalis Jacq. (swamp bloodwood), with their

impressive ribbon buttresses. Remnants of this alluvial swamp forest in the subtropical moist forest life zone remain near Dorado, on the north coast of Puerto

Rico, and at La Boquilla, north of Mayagüez. Pterocarpus is reviewed in the wetlands section.

Throughout the tropical world, the subtropical moist forest life zones are

among the most intensively used by humans. Pasture seems to be the predominant

land use in this zone in Puerto Rico today, but sugarcane, which requires little or

no irrigation, occupied a large part of this zone in the past. Some coffee is still

grown, and pineapples are planted in drier portions of the subtropical moist forest

life zone along Puerto Rico’s north-central and northwest coast. Tobacco is also

grown extensively in certain areas, notably in the Comerío-Cidra-Barranquitas

region.

The subtropical moist forest life zone, with its intermediate moisture conditions—neither excessive rainfall, nor high irrigation requirements—is the life zone

104

Figure 25—Mangrove forest in Puerto Rico. 

L. Miranda Castro
in Puerto Rico best adapted for a wide variety of land use systems, many of which

offer potentially high yields (fig. 26). Intensive food production on the flats, forage

production on the moderate slopes, and managed tree crops on the steep slopes are all

possible here. A later section on agroecosystems describes this process and some of

the economically important species typical of this zone.

The Subtropical Wet Forest

Wet and rain forests exhibit a variety of distinguishing features observed in the 

mountain communities of Puerto Rico, including:

➢ High species diversity

➢ Presence of tall broadleaf evergreen hardwood trees

➢ Stratification of forest species into layers such as canopy, subcanopy, 

shrubs, herbs, and ground cover

➢ Many lianas

➢ Diverse epiphyte groups

➢ Buttressed trunks

➢ Presence of stranglers such as Ficus spp. (figs) and Clusia rosea Jacq. 

(postcard tree)

➢ Many plants that exhibit drip-tip leaves

➢ Cauliflory and ramiflory (flowering from main trunks and woody 

branches)

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Guide To The Ecological Systems Of Puerto Rico

Figure 26—Agriculture in the mountains of Puerto Rico.

G. Miller
Box 11. Cyathea arborea (L.) J.E. Smith (tree fern) 

In the moist tropics, ferns achieve 

their greatest size, with some growing more than 18 meters (60 feet) tall.

The fronds (leaves) of these trees may

grow 3.65 meters (12 feet) long and

exhibit a beautiful design. The fronds

come out of the top of the trunk in a

spray-like arrangement. It is said that

God created ferns just to exhibit how

creative He could be in designing

leaves.

The trunks are not at all like 

those of true trees. They are not the 

result of accumulated wood over 

years of secondary growth. Instead 

they are composed of an upright rhizome (stem) surrounded by adventitious

root bundles kept together by an outer layer of scales. The center is pith, with

a ring of vascular bundles for conduction and support.

Tree ferns can be recognized by the characteristics they have in common

with other ferns: lace-like fronds (leaves) divided into pinnae; crozier formation (that is, young leaves prior to expanding look like a fiddle head); fronds

that unroll from a coil; lack of flowers, fruits, and seeds; presence of sporangia

and spores on bottom surface of fronds. The main difference is that these ferns

are tree-like in size. Puerto Rico has five evergreen tree fern species, with

Cyathea arborea the most common and visually prominent.

At any given time, an adult tree fern will have 8 to 12 mature fronds, with

another couple in the process of emerging. When they die and drop off, they

leave a large leaf scar on the trunk. The trunk is rough and may be covered

with epiphytes. They seem to do best in well-lighted areas and often succeed

in areas following landslides and road construction. Cyathea is common to

most of the montane wet forest zones in Puerto Rico.

Tree ferns can be seen throughout much of the Luquillo and Cordillera

Central Mountain ranges. If you drive Route 191 to El Yunque, you see tree

ferns as soon as you pass into the El Yunque National Forest. If you drive

north to south on any road through the Cordillera Central, they will be 

prominently displayed along the road. Many people in the middle elevations of

the mountains plant them near their homes because of their beauty.

General Technical Report IITF-35

106

Cythea arborea (L.) Sm. (tree fern) stems,

fronds, and sporangia
107

Guide To The Ecological Systems Of Puerto Rico

The subtropical wet forest occupies much of the higher parts of Puerto Rico’s

mountains. This is a high rainfall life zone, encompassing areas with mean annual

precipitation within the approximate range of 2000 to 4000 millimeters (78 to 156

inches) per year. At most, soil moisture drops below field capacity in this zone for

only 3 months, and water deficit is very small. Significant amounts of runoff occur

in this zone during at least 7 months and, in some cases, all year. The annual runoff

in this life zone is greater than rainfall input in most areas of the subtropical dry

forest life zone.

The abundant moisture of this life zone is evident in the character of the vegetation. Epiphytic ferns, bromeliads, and orchids are common; the forests are relatively rich in species; and the growth rates of successional trees are rapid. A matforming fern, Gleichenia bifida (Willd.) Spreng. and the common tree-fern,

Cyathea arborea (L.) Sm. (box 11), form a common roadside plant cover (fig. 27).

Mature forest remnants in this life zone exist in the Carite and Toro Negro

Commonwealth Forests and in the Luquillo Experimental Forest. The zonal association of the subtropical wet forest in Puerto Rico corresponds to what is locally

referred to as the tabonuco type, named for the dominant tree, Dacryodes excelsa

Vahl (box 12). Two other very prominent species are Sloanea berteriana Choisy

(motillo) and Manilkara bidentata (A. DC.) Chev. (ausubo or bulletwood). This is

an impressive forest, containing more than 150 species of trees, and forming a

dark, complete canopy at about 20 meters (66 feet). After disturbances, the trumpet

tree, Cecropia schreberiana Miq. invades disturbed areas and rapidly closes the

canopy (box 13). A massive volume edited by Odum and Pigeon (1970), and 

continuing research by the University of Puerto Rico and the International Institute

of Tropical Forestry, makes this one of the most intensively studied forest types in

Box 11. continued

The trunks are termite and rot resistant and are ground up and used commercially by the florist industry for planters and potting medium. They burn at

low rates and historically were used for moving fire from place to place. If

transplanted, they can grow on the hot and dry south coast where they are used

as an ornamental. Unfortunately, many of the tree ferns seen out of the forest

were probably stolen from a roadside somewhere in the mountains. Most illegally removed tree ferns probably die owing to transplant shock.

For more information on this species, see Little and Wadsworth 1964 and

Proctor 1989.
General Technical Report IITF-35

the world. According to Brown et al. (1983), the tabonuco forest is found in the 15-

to 550-meter (500- to 1,800-feet) altitude zone and occupies approximately 70 percent of the Luquillo Mountains (fig. 28).

Serpentine areas, previously described for the subtropical moist forest life

zone, are also found in the subtropical wet forest life zone. The vegetation on serpentine is similar in the two life zones, except that it is greener, denser, more lush,

and most strikingly, contains more epiphytes in the subtropical wet forest life zone.

The species are almost all evergreen and sclerophyllous, giving the impression of

an anomalous wet desert or dry rain forest. Excellent examples of this association

are available in the Maricao Commonwealth Forest in southwest Puerto Rico east

of Mayagüez along Route 120 (fig. 29).

Much of the subtropical wet forest life zone in Puerto Rico is covered by successional vegetation as a result of emigration to cities of much of the former rural

108

Figure 27—Species of Gleichenia (mat fern) [left] and

Cyathea (tree fern) [right] along roadsides in the El Yunque

National Forest.

G. Miller

Continued on page 112.
Box 12. Dacryodes excelsa Vahl (tabonuco)

As you move through the lower and middle sections of the Luquillo

Mountains and similar areas in the Cordillera Central, you will encounter one of the native “dominants” of the subtropical wet forest zone. It is locally called tabonuco. Some locals also call it candlewood because its resins were

used for candle and torch production. The tree is one of the largest in the forest and can reach heights of 35 meters (115 feet), diameters of 1.5 meters (5

feet) or more, and may live for hundreds of years.

It has a tall straight trunk (bole) and may exhibit buttressing. The bark is

dark gray and frequently will show patches of accumulated white resin. If you

encounter it on a trail, be sure to pinch off a piece of the resin and smell it. It

has a distinctive odor like turpentine and, when burned, the resin acts as an

insect repellent. The leaves are pinnately compound, with five to seven leaflets. It is referred to as a dominant because in the 200- to 850-meter (700- to

2,800-foot) zone, it is one of the trees with high basal area. It also has high

commercial wood value.

It grows best on deep acidic clay-based soils that drain well. They frequently occur in groups on ridges where the trees are connected by their roots and

form tree unions (p. 131, figure). Their habitat is usually on the top of ridges

where they can secure themselves on large rocks. The formation of tree unions

and the wrapping of roots around rocks allow tabonuco trees to resist hurricane

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Guide To The Ecological Systems Of Puerto Rico

Map of Dacroydes excelsa Vahl (tabonuco) tree union in the Bisley watersheds, Luquillo

Experimental Forest.
General Technical Report IITF-35

Box 12. continued

winds. Tabonuco is a tree that 

produces distinctly male and female

trees, a condition called dioecism 

(two separate houses). The flowers 

are small and green and result in a

grape-sized, one-seeded fruit being

formed. Flowering occurs from May

through November, with the drupe 

fruit development occurring in the

October to December period. The 

fruits are used by the endangered 

Puerto Rican parrot. After dispersal, 

the seeds germinate within a few 

weeks on the steep slopes of the mountains under the low light of the canopy.

Most will not survive, but those that do may emerge from the seedling or

transgressive state when a gap in the canopy occurs. The seedlings are quite

tolerant to shade. The largest tabonuco in Puerto Rico is located in Luquillo. It

is 38.4 meters (126 feet) tall, 14 meters (46 feet) in crown cover, and 4.2

meters (13.8 feet) in circumference.

This native hardwood species is excellent for furniture and cabinet production. It shows good working characteristics such as ease of planing, sawing,

turning, and sanding. It finishes well and is sometimes used as a mahogany

substitute because the wood has a reddish color.

Tabonuco was not significantly damaged in Hurricane Hugo. If you take

the “Big Tree Trail” in the Luquillo Mountain Recreation Area, you will see

many mature trees that resisted being blown over or snapped. More commonly, their crowns were blown away. The survivors are now well on their way to

reforming their crowns, but there are still gaps and obvious evidence of serious crown loss in all of the tabonucos in that area of the forest. You will also

be able to see the other trees profiled in this section along the trail or near the

parking area. The “Big Tree Trail” can be accessed off Route 191 just below

the main recreation area parking lot. Parking is available at the trail head.

There are educational signs along the trail describing the forest and its inhabitants. At the bottom of the trail is located the beautiful La Mina waterfall. Plan

on an hour or more for your round trip. Wear comfortable footwear. 

For more information on this species, see Little and Wadsworth 1964,

Lugo and Wadsworth 1990, and Walker 1991.

110

Dacroydes excelsa Vahl. (tabonuco) leaves,

flowers, and fruit
Box 13. Cecropia schreberiana Miq. (trumpet tree) 

The American tropics has a group of 

trees very important in forest succession. When small gaps occur as a

result of individual tree death or large

gaps from landslides, hurricanes, or

on the fringe of agricultural deforestation, one of the first trees to invade

these sites is Cecropia. It is a very

important Neotropical successional

genus that has nearly 100 species. In

Puerto Rico, the common species is 

C. schreberiana (or peltata).

Cecropia schreberiana is a common tree in Puerto Rico because 

much of the island is successionally

responding to disturbance. It grows best in sunny openings provided they do

not exceed a certain high temperature. Because of this, it will not invade pastures, certain landslides, or very large gaps. It produces shade and protects the

soil. It is one of the fastest growing trees reaching heights of 4.6 meters (15

feet) in a couple of years. One of its interesting botanical features is that it has

a hollow stem and trunk system when young. It can be cut down with a pocket

knife. The branches remain hollow, but the trunk solidifies as it ages. Although

Cecropia can achieve great size, its wood value is low because its early maturity and short life of 20 to 30 years, make it soft, weak, and brittle. It can be

used for paper, model toy production, fishing floats, and for musical instruments (thus the name trumpet tree). The largest C. schreberiana is found in

Adjuntas and is 27 meters (90 feet) tall, with a crown spread of 18 meters (59

feet).

The leaves and petioles are quite large, with widths of 0.3 to 0.76 meter 

(1 to 2.5 feet). Visitors to the rain forest often refer to them as “umbrella trees”

because when caught in a rain shower they use Cecropia leaves as makeshift

umbrellas. The leaf blades are simple with 7 to 11 lobes, with the same number of large veins arranged palmately. The leaf’s color is very prominent from

a distance. The top (dorsal) is green, but the bottom (ventral) surface is white.

The white color is due to dense white pubescence (hair). As the wind blows

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Guide To The Ecological Systems Of Puerto Rico

Cecropia schreberiana Miq. (trumpet tree)

leaves, flower, and fruit
General Technical Report IITF-35

Box 13. continued

these large leaves over, they switch position and whole hillsides may look like

a field of lights as the white undersides show up. In the field you can use their

presence to signify a successional site.

Cecropia produces large terminal buds. Individual trees are either male or

female (dioecious). The female inflorescence results in large numbers of oneseeded fruits frequently eaten by frugivorous bats and birds, including the

endemic Puerto Rican parrot. Flowering and fruiting goes on throughout the

year, and the animal vectors continually add them to the forest seedbank.

For more information on C. schreberiana see Brokaw 1998, Little and

Wadsworth 1964, Silander 1979, and Silander and Lugo 1990.

112

population. People left the land owing in part to the inappropriateness of most of

the subtropical wet forest life zone for agriculture. On these abandoned lands, 

Piper aduncum L. (pepper or higuillo) often forms nearly pure stands.

During the 1800s, large tracts of forest were modified to plant coffee, which

was heavily exported to the United States and Europe where it was considered a

superior product. Much of this life zone, particularly in the western portion of the

island, is still covered by coffee plantations, but to a lesser extent than formerly. 

Figure 28—View of a canopy of the subtropical wet forest. 

G. Miller
A coffee plantation, consisting of an overstory of trees, a middle layer of coffee

bushes, and a ground cover, is an agricultural ecosystem physiognomically resembling the forest it replaces. Shade-grown coffee has historically been a stable and

successful land use in many wet, mountainous tropical areas. (See the discussion

on coffee presented in the “Agroecosystems” section that follows.) Some sugarcane

was also grown in this life zone, as no irrigation water was required. The dominant

trend in land use, however, as in other areas of Puerto Rico, is grazing. Pasture

management in the subtropical wet forest life zone can be difficult owing to both

the vigorous growth of weedy herbs and vines and problems of soil compaction.

Perhaps the greatest value of the subtropical wet forest life zone in Puerto Rico

is as a source of runoff that supplies water to the drier coastal areas where the population is concentrated. Future land use planning of areas within the subtropical wet

forest life zone should certainly recognize the fact that any land and forest manipulations here may have very important effects on downstream water yield and

quality.

The Subtropical Rain Forest

This is the wettest of the subtropical life zones with a lower rainfall limit of about 

4000 millimeters (150 inches). It occupies very little area in Puerto Rico, occurring

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Guide To The Ecological Systems Of Puerto Rico

Figure 29—Vegetation cover, including an Agave, in the Maricao Forest in the mountains of western

Puerto Rico.

G. Miller
General Technical Report IITF-35

only in a single crescent-shaped band

on the windward faces of the Luquillo

Mountains. It lies wholly within the

Luquillo Experimental Forest. This life

zone is characterized by a superabundance of precipitation. The water

regime at La Mina indicates that the

soil is at field capacity much 

of the year. The annual total of 3400

milli-meters (130 inches) of runoff is

more than twice the annual rainfall

input received by most areas of the

world. The constantly wet soil eliminates water as a potentially limiting 

growth factor in this environment, but 

oxygen stress, which can inhibit root

respiration, may exert an important

influence on plant growth.

The species found here are the

same, for the most part, as those 

found in the surrounding subtropical 

wet forest. This may be due, in part, to the fact that water is not a limiting factor in

either of these two life zones. The main features of the subtropical rain forest are

the high frequency of Prestoea montana (Graham) Nichols (sierra palm, fig. 30)

and a superabundance of epiphytes. No tree stem, building, or fencepost escapes

colonization, and most leaves, even those in the upper canopy, are covered with

epiphytes. One of the floristic components of this zone are orchids. The spiny tree

fern, Nephelea portoricensis (Spreng.) Tryon, is more abundant here than in the

subtropical wet forest. More detailed information on sierra palms (box 14), epiphytes (box 15), and orchids (box 16) follows.

Because of the small area it occupies, the subtropical rain forest life zone in

Puerto Rico is primarily of academic interest, recreational purposes, and watershed

and conservation value. Last year, nearly half a million people visited the recreation area at La Mina. The Baño de Oro Natural Area, much of which lies in this

life zone, may be the only place in the world where an example of mature vegetation of a subtropical rain forest life zone is likely to receive long-term protection

while still being readily accessible to the public.

114

Figure 30—Prestoea montana’s (Willd.) H.E. Moore

(sierra palm) fronds, flowers and fruits.

Continue on page 125.
Box 14. Prestoea montana (R. Graham) Nichols. (sierra palm) 

As this tree’s common and scientific names imply, it is found in the mountains. This palm forms an almost continuous zone in sections of the upper

reaches of the Luquillo and Cordillera Central Mountains along high-elevation streams, ridges, and steep slopes. It forms a community type sometimes

referred to as the “palm brake.” It is quite distinctive when viewed from the

air or the observation tower on Mount Britton in the Luquillo Forest. These

forests exhibit simple community structure and have few associated species.

Its elevation ranges from 60 meters (197 feet) to 1000 meters (3,280 feet) and

is found throughout most of the West Indies.

The tree is attractive throughout its life and is colorful when flowering and

fruiting. Frequently the trunk is full of epiphytes, in particular the brilliant red

bromeliad, Guzmania berteroniana (Schultes) Mez. Sierra palms do not attain

the large size of many low-elevation palm species but will grow to 15 meters

(50 feet) on good sites. Their trunks are straight and terminate in a cluster of a

dozen or so attractive pinnately compound leaves that can grow to 6 meters

(20 feet) or more in length. On average, four new leaves can be produced each

year. When the old leaves drop, they leave a large leaf scar that circles the

trunk. Just below the crown, one or more inflorescences (panicle) will develop

full of hundreds of small white male and female flowers. This species is a prolific fruit and seed producer, with small and black fruits about the size of a

small marble. They do not look like the fruits of coconut palms. Sierra’s fruits

are one of the primary foods in the diet of the Puerto Rican parrot and are also

used by a variety of other birds. Sierra palms flower and fruit throughout the

year. The palms are frequently anchored to boulders or the forest floor or

stream edge by a large number of adventitious prop roots. When young, the

roots appear pink and often show numerous large tubercles. This palm is a

slow grower with vertical extension measured in centimeters (inches) per year

and not meters (feet) as is the case for some tropical trees. According to Lugo

and Battlle (1987), mean age of a population of 32 adult trees in the Luquillo

Forest was 61 years.

Sierra palms are native to Puerto Rico (not endemic) and are the dominant

tree in terms of sheer numbers in the middle and upper elevations of the

mountains. Robinson (1997) estimated that there may be 800,000 mature sierra

palms in the Caribbean National Forest and that the tree is present in higher

numbers in both the tabonuco and palo colorado forest types than the species

for which these forests are named. Sierra palms are not so much altitudinally

controlled as they are controlled by soil conditions and degree of slope. They

115

Guide To The Ecological Systems Of Puerto Rico
General Technical Report IITF-35

Box 14. continued

tend to grow in areas that may be extremely wet, rocky, or subject to erosion,

that is, streambanks and unstable slopes. As such, they appear as patches in

these habitats in elevations above 457 meters (1,500 feet) and cover more than

10 percent of the Luquillo Mountains. Because they frequently occur in very

wet areas, some people consider them to be a facultative wetland species.

Strong winds, steep slopes, saturated soils, and periodic hurricanes are major

contributors to sierra palm mortality. Its thin stems and ability to shed its

leaves increases its survival rate. They are resilient following hurricanes and

are able to leaf out fairly quickly. If they have large populations of epiphytes

on their stems, they may be vulnerable to windthrow.

Sierra palms have limited economic value. On occasion they are planted

ornamentally, the largest individuals may yield palm planks, the bud can be

consumed for food, and their fronds have been used as thatch. The real value

of this species is its ability to grow in and stabilize high-elevation soils, providing food for animals. For the student or the tourist it is also a pretty tree

and adds to the tropical forest experience.

One thing that becomes evident as you move up in elevation through the

various forest zones is the changing size of the sierra palms. In lower elevations of say 600 meters (2,000 feet) where there is less rainfall and warmer

temperatures, the adult trees are considerably taller, many approaching the 15-

meter (50-foot) size class. As you approach 915-meters (3,000-feet) their size

decreases to 3 to 6 meters (10 to 20 feet). The areas where they grow as solid

stands will be considerably cooler, moister, and windier and soil conditions

will be less stable. These sites constitute the upper elevation palm brake forest

type.

The easiest place to see sierra palms is probably in the El Yunque area of

the Caribbean National Forest. Any trail leading away from the El Yunque

Recreation Area will provide access to hundreds of them. Be sure to notice

root structure with their pink root cap zone. Take a pocket knife along and cut

longitudinally through a root in order to see the zones. Also, be sure to examine the many epiphytes, especially bromeliad “well” plants that will be growing on their trunks. As you change elevation, observe the changing size of the

adult trees. If you are quiet—and lucky—you may be able to hear or see the

endemic parrot feeding on its fruits.

For more information on this species, see Bannister 1970, Frangi and

Ponce 1985, Little and Wadsworth 1964, Lugo and Battlle 1987, and Lugo 

et al. 1998.

116
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Guide To The Ecological Systems Of Puerto Rico

Box 15. Epiphytes

Epiphytes are plants that grow on 

other plants or other objects and are 

frequently called “air plants” because

they grow up in the air and are not

directly attached to the soil. Although

they look parasitic, they do not penetrate host tissue, so they do not cause

direct harm to the host. They use the 

host for mechanical support in order to

gain access to light. They are sometimes referred to as structural parasites,

in that they will use space on a host

which can reduce photosynthetic surface, and on occasion, may cause a 

host plant to loose limbs or fall over

owing to the extra weight, especially 

during major storms. Epiphytes are 

photosynthetic and produce their own 

food. Their water and necessary nutrients are obtained from rain, dew, clouds,

accumulated humus, and stem/leaf leachate from the host plant or other associated epiphytes. There are many types of epiphytes, and there are representatives from a number of flowering plant families, with the bromeliad

(Bromeliaceae) and orchid (Orchidaceae) families two of the best examples.

Lower nonflowering plants such as ferns, mosses, liverworts, and algae also

exhibit many epiphytic species. There are even epiphytic cacti. Approximately

10 percent of all seed plant and fern species are epiphytic.

Canopy research is helping us to have a better understanding of the forest.

The contribution of epiphytes is being investigated more thoroughly as we

develop systems that permit safe access to the canopy. Many species will be

described and new functional relationships will be discovered in the future. We

suspect that over half of all orchids (more than 10,000 species) and up to 10

percent of all flowering plants and ferns are epiphytic. Some epiphytes are

able to fix nitrogen, and many of the “well or tank” epiphytes may support

more than 200 other species. A well epiphyte is one whose densely packed

leaves collect water in their axils, creating small pockets of water such as 

Generalized view of epiphytic growth in a

tropical rain forest.

G. Miller
General Technical Report IITF-35

Box 15. continued

found in many bromeliads. Many animals are able to complete their life cycle

in proximity to its host epiphyte. This ability to trap water and nutrients

aboveground creates a small favorable microenvironment, often called

miniecosystems. Algae, bacteria, fungi, protozoans, many insects, and even

tree frogs are found there. They are often visited by lizards, spiders, scorpions,

and birds for taking of prey.

Epiphytes are found in many habitats in the tropics. Any rain forest zone

will exhibit a high abundance because most require high humidity, but they

can also be found in dry forests. As you pass through any town in Puerto Rico,

you are likely to see them growing on power and telephone lines or in the

trees of the town’s plaza. They are found throughout Puerto Rico from the

highest and wettest zone in the montane rain forest, to the very dry habitat of

the Guánica Dry Forest or even the coastal mangrove forest. Many species

have special water-absorbing tissues on their roots and/or shoots, which promotes uptake of moisture from the atmosphere. Others will have swollen

stems called pseudo-bulbs that permit water storage.

Many epiphytes exhibit unique growth forms that promote their existence

aboveground. They have minimal roots mostly for attachment, but their overlapping leaves form a series of reservoirs (thus the name well or tank) that 

collects water along the central stem. Their leaves have specially adapted

water-absorbing cells at their bases. The various water sources, accumulated

dust, organic debris washed from above, and mycorrhizal fungi (in orchids)

provide the necessary nutrients. Many epiphytes produce brightly colored

flowers or bracts to attract pollinators. Orchids are notable for this and the

bizarre animal designs that their flowers exhibit (see box on orchids that 

follows). Many bromeliads produce sticky seeds that glue the seed or seedling

in position until it is established on its host.

The size of epiphytes is highly variable, and they are classed accordingly.

Macroepiphytes include the larger vascular plant groups: orchids, bromeliads,

cacti, and ferns. Microepiphytes include the lower plants: mosses, liverworts,

lichens, and algae. Those that grow on branches and trunks are referred to as

epixylous, and those that inhabit leaf surfaces are referred to as epiphyllous.

There are four classes of epiphytes. All are common to Puerto Rico.

118
Box 15. continued

➢ Proto-epiphytes are least specialized and least protected against

drought. They exhibit a velamen (water-absorption structure around

roots), and some are succulent or with bulbous stems as in many

orchids.

➢ Nest or bracket epiphytes form complex root masses interwoven

with accummulated organic debris. They produce large multiplebranched fronds that aid in debris collection. Ex.: Platycerium 

bifurcatum (staghorn fern) and Asplenium serratum L. (bird’s nest

fern).

➢ Hemiepiphytes develop long aerial roots that can reach the 

ground where they may gain access to water, as in some Ficus

(fig) species.

➢ Tank epiphytes are representative of one family, the Bromeliaceae

(found only in the Neotropics). Bromeliads create miniature water

tanks in the axils of their leaves in which water, debris, and nutrients are trapped and thus create a favorable environment for many

other species. The genera Guzmania and Vriesea are described 

later in this section.

Some unusual tropical plants start out as epiphytes. Stranglers are trees, 

such as certain figs (Ficus), that ultimately “strangle” their host and 

assume their structural position in the forest. They start as epiphytes in an 

old canopy tree and then outlive their structural host. All the while they send

down roots that eventually grow together forming a new outer trunk, thus producing the appearance of the strangling effect. Clusia rosea Jacq. (autograph

tree) described earlier is another good example of this growth strategy.

In Puerto Rico, one of the most interesting places to see epiphytes is along

one of the many trails associated with the El Yunque Recreation Area in the

Caribbean National Forest. Access to the recreation area is via Route 191 at

the town of Palmer. Palmer is on Route 3, 30 kilometers (18 miles) east of San

Juan. A brochure with maps is available at El Portal as you enter the forest.

Trail sections near the parking area are improved and may have a paved surface. As you get farther from the trail heads, trail surfaces become more rutted. 

Hiking shoes are recommended for those planning to hike to one or more

of the summits in the area. On any given day, you should expect a rain shower.

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Guide To The Ecological Systems Of Puerto Rico
General Technical Report IITF-35

Box 15. continued

An interesting exercise is to find a recently downed tree in one of these

habitats and try to determine how many different types of epiphytes are present. How are they distributed on the tree or branch? Look for any “well” plants

present and examine their structural features, as well as animals present. Other

features to look for are trapping of organic matter, water conservation mechanisms such as succulent leaves, leaf/stem scales, waxy covering of the epidermis, aerial roots that photosynthesize, bright colors in the inflorescence that

helps to attract pollinators, and evidence of the presence of stranglers. Many

trees in the El Yunque area have their trunks totally covered in epiphytes.

Puerto Rico has a diverse epiphytic flora, including 36 species in the

Bromeliaceae family. Some of the common species that you will likely

encounter as you visit different ecosystems are:

Tillandsia—This genus has 15 species in Puerto Rico. The most common 

is Tillandsia recurvata (L.) L., often called ball moss. It can be seen growing as a small ball on power or phone lines along roads in the coastal plain. 

It is especially common in trees on the south coast. Tillandsia usneoides

(L.) L. or Spanish moss is the common epiphyte found in dense populations

throughout much of the outer coastal plain of the Southeastern United States

growing on live oaks and bald cypress trees. Spanish moss is much rarer in

Puerto Rico but can be seen in some of the coastal hills near La Parguera 

and hanging in some trees south of Arecibo in the karst region. Both species

are bromeliads and exhibit special adaptations to conserve water. Although

they appear to be lichen or fungus-like, they are photosynthetic and are 

higher flowering plants. They produce capsule fruits and plumed seeds that 

are wind dispersed. This is the largest bromeliad genus with the greatest 

geographic range. One of their primary dispersal agents is the wind associated with hurricanes.

Guzmania—This is another very common bromeliad epiphyte found in most 

forested mountainous areas of Puerto Rico. There are four members of this

genus in Puerto Rico. The common species is Guzmania berteroniana

(Schultes) Mez. This tank epiphyte can be seen throughout the montane rain

forest on El Yunque, which is its type habitat. It ranges from 365 to 1158

meters (1,200 to 3,800 feet) in Puerto Rico and nearby Dominican Republic.

On occasion, you will see it growing on the ground as a terrestrial plant. The

inflorescence consists of brilliant red bracts, with small yellow flowers. The

120
Box 15. continued

leaves are dark green and form a welldeveloped axillary tank system. When 

in flower, they look like red candles

hanging off tree trunks. This genus is

common throughout the Andean cloud

forests of Ecuador and Colombia where

they can grow at elevations exceeding

3050 meters (10,000 feet).

Vriesea—This is another bromeliad 

native to high-elevation and elfin 

cloud forests where it is quite cool. 

The El Yunque area is the type habitat 

for Vriesea sintenisii (Baker) L.B. Sm. 

& Pitt. It has green leaves in shady 

habitats but turns bright red in welllighted areas. It also is a “well” plant and produces a large one-foot spike

inflorescence of white flowers and red bracts. This genus is widespread

throughout cloud forest regions of the Neotropics. Some of the species of this

genus are important in the commercial house plant trade. They grow to elevations of 3050 meters (10,000 feet) in mainland Neotropics. Most are epiphytic,

but some are cliff dwelling.

For more information on epiphytes, see Lüttge 1989, Padilla 1973, Patzelt 

1973, Richards 1996, Royal Botanic Gardens 1996, and Zahl 1975.

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Guide To The Ecological Systems Of Puerto Rico

G. Miller

Common epiphytes (Guzmania berteroniana

[Schultes] Mez.) growing on tree trunks in

the mountains of Puerto Rico.

Box 16. Orchids

Orchids belong to the monocot family Orchidaceae. This family is very 

species diverse, with more than 20,000 species (some estimates say 25,000)

distributed throughout the world, especially in the tropics. Puerto Rico has

144 species of native orchids (5 percent of the flora). The flowers are unique,

beautiful, and in some cases, bizarre. They are bizarre in terms of their shapes

and colors, which may resemble their animal pollinators. They are among the

top six plants sold by the cut flower industry. Some rare species are worth
General Technical Report IITF-35

Box 16. continued

$500,000, and, on several occasions, deaths have occurred in their procurement or possession. Rare orchid collectors are periodically taken hostage and

held for ransom, as recently happened in Colombia, South America. Orchid

poaching and smuggling is an international business today. Many rain forest

trees will be cut in order to access the orchids growing as epiphytes on their

branches. Over half of all orchids are epiphytic.

Orchids are mostly concentrated in the Asian and Neotropics where the

majority are epiphytes (hundreds of genera) growing on trunks or branches of

trees. They also occur in the temperate and Arctic zones where they are mostly

ground dwellers. Flower morphology reaches its zenith in complexity and specialized parts in the orchids. Many orchids have evolved very special symbiotic relationships with their pollinators, and many produce flowers in the shape

or color of the species that pollinate them. Various flies, bees, wasps, ants,

moths, butterflies, beetles, and hummingbirds all serve as orchid pollinators,

and each group is attracted to a different type of flower. Probably the best

example of this is found in the euglossine orchids, which are singularly pollinated by euglossine bees after a pseudo-copulation. The orchid flowers smell,

look, and feel like the female of the bee species.

When successful pollination and fertilization has occurred, the embryos

develop inside a fruit that is typically a capsule. Thousands of seeds about the

122

G. Miller

Cultivated orchids of today were selected and bred from tropical forest species
Box 16. continued

size of dust specks develop. When mature, the seeds are spread by wind. The

seeds lack nutritive endosperm, essential for normal embryo and seedling

development. Because of this, it is critically important that the tiny seeds be

blown to a suitable substrate with an essential fungus present. To grow and

develop, the orchids must have a mycorrhizal relationship with the fungus.

This is another example of a mutualistic symbiosis. The fungus is thought to

receive vitamins or other growth substances, and the orchid benefits by receiving carbohydrates for its initial growth and development into a seedling that

can then support itself through photosynthesis. This mycorrhizal relationship 

is one of the reasons why home gardeners find it difficult to raise their own

orchids.

Without these specialized pollinators, sexual reproduction cannot occur.

These elaborate floral/animal designs and colors give these plants added allure

and economic value. Many orchids are very large and persist for weeks after

opening, others are quite small and inconspicuous. Orchid flowers are typically small. Most of the orchids used for commerce are the result of hybridization or are some of the rare larger flowering wild species. Because of protection and increasing rarity, many orchids are being reproduced by tissue culture

today. This allows many individuals to be grown quickly from expensive

hybrids. Not all orchids are valuable for their flowers. Some are valuable for

their fruit, with the vanilla orchid as the best example (Vanilla planifolia B.O.

Jackson). Vanilla comes from the fruit of an epiphytic vine, and in Puerto Rico

it is found in places such as the Guánica Forest. Guánica Forest is one of the

dryest habitats in Puerto Rico and only five orchid species have been identified from there. The wettest areas in the tops of mountains also have reduced

numbers of orchids. Greatest species diversity of orchids occurs in middle elevations, with moderate rainfall, such as in the Maricao Forest in the western

end of the Cordillera Central Mountains. Again, it appears that Puerto Rico’s

geographic position as the easternmost island of the Greater Antilles chain

places it furthest away from orchid-rich mainland Central and South America.

It has the fewest species of orchids of any of the Greater Antilles. Puerto Rico

has 14 endemic orchids, about 10 percent of the orchid flora. There have been

recent alien introductions of orchids to Puerto Rico, and they are locally naturalized (Ackerman 1992). Unfortunately, Puerto Rico’s largest and most showy

orchids are the objects of collectors of wild orchids and most are suffering

under this pressure. In some instances, their populations have been greatly

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Guide To The Ecological Systems Of Puerto Rico
General Technical Report IITF-35

Box 16. continued

reduced, as in the case of Psychilis kraenzlinii (Bello) Sauleda (red butterfly

orchid). This is an endemic orchid, and it is naturally uncommon. It is typical

of the moist karst and lower elevation mountain forests. It grows as an epiphyte and occasionally on the ground. It produces large, bright red flowers,

which form all year long. It takes years for this species to reach sexual maturity, one of the reasons for its vulnerability.

In Kathryn Robinson’s (1997) research on the Luquillo Mountains, she

found that “more people ask about orchids than about any other flowering

plants, but few actually see them.” This relates to the fact that, as indicated

earlier, most orchids are small, and the majority are epiphytes, in other words,

growing off the ground on tree branches in the canopy. In many cases it takes

a trained eye to even spot a wild orchid, except for a few of the very large

flowering species, which in most cases are rare. As is the case with many

plants and animals, the more rare a species is, the more someone desires it or

is willing to pay for it. Certainly this applies to orchids. Puerto Rico has a rich

flora and, as cited earlier, the orchids are second in abundance in the monocots

and fourth largest family overall. To help the native flora:

➢ Get educated about rare, threatened, and endangered species.

➢ Help to promote preservation of critical habitats.

➢ Do not take wild plants—most will die before they are successfully

transplanted.

➢ Enjoy them in the wild—hopefully, future generations will be able 

to find them and appreciate them just as you have.

➢ Do not buy plants from local vendors that do not have verification

tags as to species name and growth information. They are likely taken from

the wild.

Two places will guarantee the visitor an opportunity to see orchids. One is 

in the wild, the other is a garden. The easiest place to see them in the wild is

along the trails in the El Yunque Recreation Area of the Luquillo Mountains.

There are 80 species native to this area. Many will be growing at ground level

along the trails of the recreation area. These will be 25 to 37 centimeters (10 to

15 inches) tall, with an upright flower stalk (raceme) and numerous small

white flowers. Two common ground-dwelling orchids are (Octadesmia montana (Swartz) Bentham) and the common genus Spiranthes spp. (Ladies tresses). Other species will be growing as epiphytes above your head on the major

branches of the trees. To see these, you will probably need binoculars.

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Box 16. continued

The other place to see orchids is in the garden display area of the

Botanical Garden associated with the University of Puerto Rico at Río Piedras

described earlier in the “Flora of Puerto Rico” section. In the upper section

there is an outdoor display area with various species of large showy orchids.

They are easy to access to take photographs. There is no entrance fee and

parking is adjacent to the access trail through the garden. Many other species

of native and introduced species are on display, as well as numerous other 

epiphytes. Unfortunately, many of the orchids were severely damaged during

Hurricane Georges and funds have not been appropriated for their replanting.

For more information on orchids, see Ackerman 1995.

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Guide To The Ecological Systems Of Puerto Rico

The Subtropical Lower Montane Wet Forest

There are two lower montane life zones in Puerto Rico (wet and rain). Figure 31

illustrates the typical species and forest types in this and adjacent zones. The wet

forest zone is by far the most extensive. It occurs in both the eastern and central

parts of the island up to the summits of most mountains above 1000 meters (3,280

feet) and occasionally extending down to almost 700 meters (2,300 feet). No peaks

in Puerto Rico are high enough to encounter low temperatures necessary for the

occurrence of the next highest, or montane altitudinal belt. The soil is at field

capacity all year, and runoff occurs each month, but the total of 1700 millimeters

(67 inches) annually is only about half of that at La Mina.

The colorado forest type, named for the common tree Cyrilla racemiflora L.

(palo colorado or swamp cyrilla), corresponds to mature vegetation of the zonal

association in the subtropical lower montane wet forest. Cyrilla racemiflora (box

17) is the same species that grows as a shrub or small tree in the wet swamps in the

Southeastern United States. However, in the mountains of Puerto Rico it can grow

into a large, reddish-barked canopy tree, and the hollow trunks of the older individuals are the main nesting sites for the nearly extinct Puerto Rican parrot (Amazona

vittata). This forest is characterized by open-crowned trees, many of which have

their leaves grouped toward the ends of branches. This forest is poorer in species

than the adjacent tabonuco forest. Wadsworth (1951) reported that only 53 species

have been found in this forest type, compared to more than 150 species in the adjacent tabonuco forest type in the subtropical wet forest. The colorado forest covers
General Technical Report IITF-35

126

Figure 31—Species and forest types typical of the lower and upper elevations of Puerto Rico’s mountains.
Box 17. Cyrilla racemiflora (palo colorado)

This tree is the species typical of the 

wet montane palo colorado forests. It 

has red bark and leaves at maturity, thus

its common name palo colorado or “red

tree.” This is the preferred species for

nesting by the endangered Puerto Rican

parrot. It is said that this species has 

individuals older than 1,000 years in

Puerto Rico and that some achieve

greater than 2.5 meters (8.2 feet) in

diameter. Examination of these giant

individuals in the field indicates that

many of these large individuals are the

result of coalescence of multiple stems. 

This is one of the largest diameter

trees in Puerto Rico. Interesting is the

fact that in the temperate zone, this same species grows no larger than a headhigh shrub and never achieves tree size in North Carolina and adjacent coastal

states. This is a wetland species typical of coastal bogs called pocosins and

goes by the common name of “Titi.” In Puerto Rico, Cyrilla may grow up to

20 meters (60 feet), but on exposed ridges it may grow in the shrub form. The

largest palo colorado in Puerto Rico is in Luquillo, and it measures 21 meters

(69 feet) tall, has a canopy spread of 10.4 meters (34 feet), and a circumference of 6.45 meters (21.2 feet).

The leaves are simple and its flower is an easily recognized raceme, with

numerous densely packed white flowers. The small ovate shaped fruits are

drupes. Reproduction occurs throughout the year. Its growth and wood characteristics make it low value for commerce. Its primary value is as a fruit producer and nesting cavity supplier to wildlife. The species undergoes heartwood

rot, thus many trunks and damaged branches have hollows needed by birds

such as the Puerto Rican parrot, as they cannot fabricate their own nest 

cavities.

The species initially appeared to be a primary forest species owing to its

size and presence, but further investigation seems to indicate that it also functions as a secondary species that takes advantage of gaps. There seems to be

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Guide To The Ecological Systems Of Puerto Rico

The stems, leaves, and inflorescence of

Cyrilla racemiflora L. (Palo colorado)
General Technical Report IITF-35

128

Box 17. continued

strong correlation with the stand values of Cyrilla and the frequency and size

of hurricanes, that is, more time between hurricanes seems to lessen Cyrilla

seedling regeneration and produces larger diameter classes of older individuals

(Weaver 1986). They may be primary species in extremely wet sites like

Prestoea montana (R. Graham) Nichols. (sierra palm) is in the palm brakes

and Rhizophora mangle L. (red mangrove) is along the coastal fringe.

For more information on this species, see Little and Wadsworth 1964 and

Weaver 1996.

Figure 32—Colorado forest at 700 meters (2,300 feet) on the windward aspect of the Luquillo

Experimental Forest.

A.E. Lugo

nearly 17 percent of the Luquillo Mountains and is found above 600 meters (2,000

feet). A description of the palo colorado follows. Figure 32 illustrates a typical

stand in the Luquillo Experimental Forest.

Two additional associations are commonly found in the lower montane wet 

forest life zone in Puerto Rico. The first of these is a cloud forest, generally

referred to as the elfin woodland, mossy forest, montane thicket, or dwarf forest

(fig. 33). The most exposed ridgetop vegetation is characterized by twisted gnarled
trees less than 7 meters (23 feet) tall, with small diameters, a large number of stems

per unit area, and extremely slow growth rates. All trees here are evergreen and

sclerophyllous, and the leaves tend to be grouped near the ends of the branches.

Common trees found in the elfin forest include: Ocotea spathulata Mez. (nemocá),

Eugenia borinquensis Britt. (guayabota), Tabebuia rigida Urban (roble de sierra),

Magnolia splendens Urban (magnolia), and Clusia rosea Jacq. (autograph tree).

Box 18 describes Tabebuia rigida Urban. This forest is unique in that more than

half of its dicotylodonous trees are endemics. In protected areas on mountain

ridges, elfin forest will grow much taller and straighter. Weaver (2000) refers to 

it as Puerto Rico’s endemic forest.

Decomposition is apparently slow in this association, and the upper soil cover

seems to be almost pure organic matter, whereas the subsurface soils are clayey and

oxygen-deficient. Tree roots form a tight, complete mat on the surface and do not

appear to penetrate the soil very deeply. Another impressive feature of this association is the epiphyte load of ferns, mosses, liverworts, algae, and bromeliads, which

cover almost all stems, even those perfectly vertical and smooth-barked. This forest

is restricted to ridges and peaks above 750 meters (2,460 feet) and covers about 

2 percent of the Luquillo Mountains.

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Guide To The Ecological Systems Of Puerto Rico

A.E. Lugo

Figure 33—Elfin forest at 1050-m (3,400 feet) near Pico del Este in the Luquillo Experimental Forest. 
General Technical Report IITF-35

In an event entirely unexpected for an area as well known biologically as

Puerto Rico, Kepler and Parkes (1972) discovered a new bird species, Dendroica

angelae (Elfin woods warbler), which is apparently endemic to this association in

Puerto Rico. It is also the habitat for rare species of tree frogs.

Several theories have been proposed to explain the low stature of the trees in

this association. Murphy (1916) felt that exposure to strong winds affected the

physiognomy of this vegetation, which he referred to as the “hurricane hardwood”

type. For a description of the impacts on the elfin forest by Hurricane Hugo in 

the Luquillo Mountains, see Weaver (1999). Gleason and Cook (1926) and Beard

(1942) also attributed it to the high winds that continually buffet these peaks,

which, when coupled with the wet soils, might produce physiological drought.

Wadsworth and Bonnet (1951) discussed water-saturated soils, with their impeded

130

Box 18. Tabebuia rigida Urban, (roble de sierra or mountain oak)

Tabebuia is one of the trees typical 

of the elfin forest found in the highest

elevations of the Luquillo Mountains.

It is a small evergreen tree found in

eastern Puerto Rico. It may grow to

9.2 meters (30 feet), but frequently in

the upper wind-swept, cloud-draped

mountains it is dwarfed and twisted,

sometimes growing to only 2.4 meters

(8 feet). The leaves are opposite, simple, elliptic, with the margins curled

under. The leaves are frequently covered with microepiphytes, while their

branches and trunks tend to be full of

macroepiphytes. They produce red

flowers that are tubular and five-lobed, and the fruits are long cigar-like brown

capsules. A distinguishing bark feature is its white inner bark. They reproduce

throughout the year. Owing to its twisted growth form, the wood has little

value. An unusual feature of this plant is that it also shows a disjunct distribution pattern as it is present in the Guánica dry forest.

For more information this species, see Little and Wadsworth 1964.

The leaves and flowers of Tabebuia rigida

Urban (roble de sierra).
drainage, as factors influencing tree growth in the adjacent palo colorado type.

Odum (1970) considered the elfin forest to be transpiration-limited, in that the 

continual cloud cover and saturated air impede transpiration, resulting in limited

flow of essential mineral nutrients from the soil into the leaves. That theory was

bolstered by the findings of Weaver in 1973 when he measured extremely low transpiration rates for several tree species in the elfin cloud forest association. Figure

33 illustrates the elfin forest in the Luquillo Experimental Forest.

A second azonal association in the lower montane wet forest life zone is the

palm brake, consisting of nearly pure stands of the Prestoea montana (Graham)

Nichols. (sierra palm). Box 30 describes the development of sierra palms.

Examples of this association are readily accessible in both the Luquillo and Toro

Negro Forests. Some of the characteristics of the palm brake include its high dominance (almost a monoculture) and a sharp ecotone with adjacent associations.

Sierra palms also extend across life zone boundaries, reaching down into the subtropical wet forest and subtropical rain forest life zones. Beard felt that the occurrence of a palm brake was related to rates of erosion and that some of the areas

where the palm formed pure stands were probably former landslides. Destruction of

all trees by hurricanes, except the sierra palm, which sheds its fronds (leaves) in

high winds and therefore does not uproot, might be another factor accounting for

pure stands in Puerto Rico. They also develop a vast network of prop roots (fig. 34)

that support them well in strong winds and heavy rains. In addition to forming

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Guide To The Ecological Systems Of Puerto Rico

Figure 34—Well-developed prop root systems of Prestoea montana (Graham) Nichols (sierra

palm) in the Luquillo mountains.

A.E. Lugo
General Technical Report IITF-35

nearly pure stands on steep soils, Prestoea is also an important component of the

mature, mixed forest. Altitudinally, palm brake forests are interspersed between

palo colorado and tabonuco forests and cover nearly 11 percent of the Luquillo

Mountains (fig. 35). The sierra palm forest is present in the 730- to 915-meter

(2,400- to 3,000-foot) altitude zone.

Because of high rainfall here, the lower montane wet forest life zone is not too

vulnerable to damage by commercial forestry or agriculture, although in some areas

dairy cattle are pastured, mostly on molasses grass (Melinis minutiflora Beauv.).

Here again, as in other life zones with exceedingly high rainfall, primary value lies

in water yield. 

The Subtropical Lower Montane Rain Forest

This life zone occupies less area than any other in Puerto Rico and is found only 

in a narrow band on the windward slopes of the Luquillo Mountains, immediately

above the subtropical rain forest life zone. Baynton (1968) measured several standard weather variables for 1 year, from March 1966 through February 1967. He

reported a mean annual temperature (based on the mean of average daily maximum

and average daily minimum) of 18.6 oC (66 oF), an annual rainfall of 4533 millimeters (178 inches), and a mean relative humidity of 98.5 percent. This area is 

subjected to strong winds and extensive exposure to clouds.

The vegetation of this life zone in Puerto Rico is very similar to that of the

lower montane wet forest life zone. The distinguishing characteristics between the

132

Figure 35—A view of the palm brake forest and elfin forest in the Luquillo Mountains.

G. Miller
two are greater abundance of epiphytes, palms, and tree ferns in the lower montane

rain forest. Most of this life zone in Puerto Rico is in the elfin cloud forest association, where much of the vegetation on the exposed ridges has a windswept

sculpted appearance. Gill (1969) documented the formation of aerial roots,

extremely abundant on many species in this association. The water-saturated soil 

is covered with a soil-free root mat. Epiphytes, most of which are leafy hepatics

(liverworts), cover everything. This forest of twisted and stunted trees and shrubs 

is found on the highest peaks in the 760- to 1070-meter (2,500- to 3,500-foot) 

altitude zone (fig. 36).

The lower montane rain forest life zone in Puerto Rico is primarily a biological

curiosity, but an invaluable one since it represents an environmental extreme and,

as such, is an excellent opportunity for investigating the response of natural ecosystems to environmental stress. It is indeed fortunate that the limited amount of this

life zone in Puerto Rico is located in the El Yunque National Forest, specifically 

the Baño de Oro Natural Area.

The term cloud forest is often used to describe forests in wet mountainous

areas in the tropics. Some authors use the term for a specific forest type, whereas

others use it generically. In general, clouds start to form in the Luquillo mountains

when moisture-laden air masses rise above 600 meters (1,970 feet). The clouds

then enter all forests at or above that elevation. Thus the elfin, palm brake, and 

palo colorado forests are all “cloud forests.”

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Guide To The Ecological Systems Of Puerto Rico

Figure 36—View of the high-elevation elfin forest. 

A.E. Lugo
General Technical Report IITF-35

Table 16—

Com

mon

plants that can

be fou

n

d along roads an

d trails in the El Yu

n

q

ue recreation area

Trees: Shru

bs: Herbs/forbs(cont.):

Cecropia schreberiana (tru

m

pet tree) Hisbiscus rosa-sinensis (rose hibiscus) Spiranthes (ladies tresses orchid)

Cyathea arborea (tree fern) Palicourea riparia (cachim

bo) Sansevieria (snake plant)

Cyathea pubescens (small spiney tree fern) Piper aduncum (com

mon

pep

per) Begonia sp

p. (begonias)

Prestoea montana (sierra palm) Bambusa vulgaris (com

mon

bam

boo) Andropogon gerardii (broomstraw)

Dacryodes excelsa (tabon

uco) Miconia prasina (camasey) Mimosa pudica (sensitive plant)

Magnolia splendens (laurel mag

nolia) Miconia impetiolaris (camasey shru

b)

Manilkara bidentata (ausu

bo) Lobelia portoricensis (P

uerto Rican lobelia)

Clusia rosea (postcard tree) Psychotria berteriana (cachim

bo) Ferns:

Buchenavia capitata (wild olive) A

diantum latifolium (maiden

hair)

Sloanea berteriana (motillo) E

pip

h

ytes: Thelypteris deltoidea (eared

woodfern)

Cyrilla racemiflora (swam

p cyrilla) Vriesea sintenisii (red leaf bromeliad) Dennstaedtia bipinnata (mou

ntain fern)

Tabebuia rigida (mou

ntain oak) Guzmania berteroniana (bromeliad) Nephrolepis multiflora (flower fern)

Tabebuia heterophylla (w

hite cedar) Philodendron oxycardium (com

mon

Dryopteris sp

p. (shield ferns)

Spathodea companulata (African tulip tree) p

hiloden

dron) Gleichenia pectinata an

d

Artocarpus altilis (breadfruit or bread

n

ut) P

hiloden

dron

giganteu

m (large p

hiloden

dron) Gleichenia bifida (com

mon roadside ferns)

Musa paradisiaca (banana tree) Pitcairnia sp

p. (Pitcairn’s bromelidad) Polypodium crassifolium (strap fern)

Inga vera (g

uaba) Man

y

mosses, ferns, an

d other lower plants. Hy

menophyllum rigidum (green film

y fern)

Ficus citrifolia (shortleaf fig)Didy

mopanax

morototoni (match

wood) Herbs/forbs: Other lower plant groups:

Ocotea spathulata (nemoca) Impatiens sultana (touch-me-nots) Marchantia sp

p. (liverworts)

Mangifera indica (man

go) Heliconia caribaea (lobster claws) Polytrichum sp

p. (haircap

moss)

Citrus paradisi (grapefruit) Coleus blumei (com

mon coleus) Lycopodium sp

p. (clu

b

moss)

Ichnanthus pallens (grass) Selaginella sp

p. (spike moss)

134
If you are visiting the El Yunque National Forest/Luquillo Experimental Forest,

see appendix 2 and table 16.

For further reading see Ashton 1989; Baynton 1968; Bridsey and Weaver 1982;

Brooks 1987; Daly 1995; Dansereau and Buell 1966; Farnsworth 1991; Holdridge

1967; Mares 1992; Miranda-Castro 2001; Murphy and Lugo 1986, 1995; Robinson

1997; Russell and Miller 1977; Wadsworth 1951; Weaver 1979, 1994, 1995; and

Weaver et al. 1999a, 1999b.

Agroecosystems

Throughout the tropical world today there is great interest in agroforestry and 

agroecosystems. These involve sustainable practices that have evolved over the

millennia in the tropics where local indigenous people developed forestry and agriculture in a mixed polyculture, sustaining aspects of both the forest’s structure and

function, and the continuous production of food crops. Agroecosystems are important because they produce many benefits such as:

➢ Locally available and constant source of wood fuel

➢ Source of small timbers for local use

➢ Source of locally grown and sold food

➢ Source of shade for crops such as coffee

➢ Litterfall to maintain or increase soil productivity

➢ Reduced soil erosion because of intact forest canopy and tree roots

➢ Interactive nutrient pump between deep-rooted and shallow-rooted 

species

➢ Continuous sustainable yields vs. shifting cultivation

➢ Shelterbelt provided by canopy species for adjacent open land 

agriculture

➢ Habitat for a variety of nonagricultural species

➢ Helps to maintain good soil moisture relations

➢ Sources of fodder for domestic animals

Many of these systems also serve as vital wildlife habitat, especially for 

Neotropical migratory bird species, many of which are common songbirds of eastern North America. A discussion of Neotropical migrant birds was presented earlier. For a review of how these habitats have been misunderstood in the temperate

zone and mismanaged in the tropics, see Jansen’s (1973) paper on tropical agroecosystems.

Unfortunately, in the case of Puerto Rico, no indigenous people remain nor is

there any real record of prior polyculturing in their population centers. There are,

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however, some small limited examples of this process being conducted by contemporary farmers in the mountains of Puerto Rico. Mixed broadleaf canopy species

with an understory of citrus (oranges, limes, grapefruit), breadfruit, bananas, and

coffee (fig. 37) can be observed in some of the more rural areas along the roads

between Adjuntas and Maricao and Lares and Utuado. Nearby mango trees frequently overhang the roads, papaya can be seen next to residences, and oftentimes

on the forest floor, cassava will be present. All of these are very useful and heavily

consumed fruits and vegetables in the tropics and require little attention other than

harvesting when mature, and periodic replanting, as in the case of bananas and cassava. Frequently, free-range chickens and possibly a tethered pig, goat, or cow will

be used to graze the area.

These small plot agroecosystems incorporate annual crops (bananas and cassava) and perennial tree crops (breadfruit, citrus, coffee, mango, and papaya). Note

that all are introduced species to Puerto Rico. All can be bought commercially at

roadside stands in the region or local markets throughout Puerto Rico and, in 

general, can be found in most produce markets of the tropical world.

These systems are important locally because they supply a vital, inexpensive,

readily available food supply. In addition, they reduce nutrient loss in mountain

soils, reduce compaction and erosion, and help maintain water quality. They 

provide vital forest structure that serves as wildlife habitat because they are not

mass harvested, as in the case of tree monocultures or forest clearcuts. The forest

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Figure 37—Overview of agroeocosystem with coffee as the understory crop. 

G. Miller
products are sustainable and have a relatively high per-unit commercial value when

taken to local markets. Rural areas often exhibit high unemployment, thus income

is generated from labor-intensive, rather than energy-intensive systems such as a

commercial monoculture, so both human and wildlife food chains are maintained in

these agroecosystems. This promotes maintenance of higher species diversity not

found in monocultures.

Following are some basics about many of the plants we now take for granted in

our local food stores, things that people may consume daily or weekly. Six plants

that grow in the tropics and are shipped throughout the world for human consumption were arbitrarily selected. Some of these, such as coffee, sugarcane, and

bananas, have such international significance that whole national economies are

dependent on their harvest with prices derived in the international commodities

markets. The so-called banana and sugar republics are well-known. They get their

names because governments in the past rose and fell based on the price of the commodity. Fixing a satisfactory price for bananas and sugar is still a very contentious

international issue and certainly affects the quality of life for millions of people in

Central and South America as well as the Caribbean. Hurricanes can have enormous impact on most of the crops, especially species like bananas and coffee,

important to family and national incomes. For instance, in 1996, Hurricane

Hortense, a low-intensity hurricane with winds of 120 to 130 kph (75 to 80 mph),

caused $128 million in damage to coffee and plantain crops in Puerto Rico.

Six economically important plants will be reviewed including sugarcane, coffee, banana, citrus, pineapple, and mango. Literally hundreds of fruits and vegetables could have been selected for review, but the ones selected are commonly

grown and used in Puerto Rico and throughout the Neotropics. All are now readily

available in produce markets in the United States and Europe.

Typical Crops of the Tropics

Sugarcane—

Scientific name—Saccharum officinarum L.

Plant family—Poaceae (Grass family)

Growth form—Perennial grass

Origin—South Pacific islands

Domesticated—India

Historical significance—Spread from India through Arab trade routes. In the 15th

century, it replaced honey as the principal sweetener in Europe where it was largely

used to disguise the bitter taste of herbal or other medicinal concoctions.

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Caribbean spread—Brought to the Caribbean in 1493 on Columbus’s second 

voyage, it was thought to be grown in Puerto Rico shortly after 1510.

Slave trade—Growing and harvesting of sugarcane was largely what gave impetus

to the establishment of slave trade in the New World. Sugar, rum, and slavery

became interdependent during the colonial period and formed the infamous “tragic

triangle.”

U.S. Revolutionary War—The imposition of the Sugar Act by British Parliament 

in 1764 caused extensive smuggling of sugar into the colonies from the Caribbean

and resulted in the sinking of the British custom boat, the Gaspee. This was the

first major action by colonists leading to the American Revolution.

Growth cycle—Sugarcane is grown as a monoculture throughout much of the 

lowland tropics and subtropics. The name “sugarcane” relates to the fact that the

plant’s stem has a high percentage of sucrose (10 to 15 percent), and the growth

form of the aerial stem is botanically referred to as a cane. The aerial stems may

grow up to 6 meters (20 feet).

Sugarcane was the dominant crop in Puerto Rico for more than 300 years. Free 

access to U.S. markets for sugar and large investments of American capital revolutionized the agricultural economy of Puerto Rico. It turned the island from subsistence agricultural economy, with some commercial success in tobacco and coffee,

to one based primarily on sugar for export. The level coastal plain with its excellent

soils and the rolling foothills adjacent to the mountains on the north and west sides

were ideal for sugarcane growth. In addition, there was a good network of access

roads. The dry south coast from Aguirre to Cabo Rojo could be irrigated to produce

excellent yields. At the height of its sugar economy in the 1930s, Puerto Rico 

annually harvested 87 000 hectares (214,000 acres) of sugarcane, and in 1940,

there were 22 sugar processing mills. By 1969, cane harvest had dropped to 68 800

hectares (170,000 acres). In 2002, there were only two cane mills operating, one at

Yabucoa (Roig sugar mill) on the east coast and the other at Aguada (Coloso sugar

mill) on the west coast. The mills are owned and operated by separate groups of

sugarcane farmers, but are heavily subsidized by the Puerto Rico government.

Sugarcane harvest and processing into its various derivative products is all but

a thing of the past. Vast acreages of cane in most coastal areas of Puerto Rico go

unharvested even though raw sugar has to be imported for processing in order to

meet the 40,000 tons of table sugar consumed in Puerto Rico each year. Sugar

prices are politically regulated and highly subsidized. As a result, U.S. consumers

pay sugar prices that are over two times the average world sugar price resulting in

$1.9 billion in added food costs yearly. Sweeteners today include a vast array of

138
products, most not having their origin in sugarcane; cane sugar supplies just 50 

percent of the world’s supply of sugar. As a result of precarious price fluctuations,

rising costs, and continual labor problems, it became no longer economical for 

U.S. sugar companies to maintain sugar operations in Puerto Rico. Vast areas in

Texas, Louisiana, and Florida are now devoted to cane production using the most

advanced mechanization systems available to the industry. Many former cane 

fields near metropolitan areas in Puerto Rico such as Bayamón, Caguas, Arecibo,

Mayagüez, and Ponce are rapidly falling to urban sprawl, highway development,

and conversion to other agricultural uses. Large sections of cane fields are reverting

to nature by natural succession. Most of the raw sugar processing mills are now

closed and wasting away in the tropical sun as sentinels to a time when Puerto Rico

was a sugar colony for both Spain and the United States. Some of the mills were

sold lock, stock, and barrel, dismantled, and shipped to large plantations in Brazil.

There is currently a proposal to bring sugarcane production back to life in Puerto

Rico. This new initiative will provide both table sugar and generate a new product,

bio-ethanol, which can be blended into gasoline. The group proposing to do this is

the Puerto Rico Bio-energy Cooperative. Ultimately, they hope to produce 45 million gallons of bio-ethanol and 59,000 tons of table sugar (azúcar).

There is a small photo museum devoted to the sugar industry at the old mill 

in Aguirre. There one can observe some classic plantation overseer houses, office

buildings, and the processing mill. As there are tens of thousands of acres of sugarcane in Puerto Rico, we will next examine its biology and historical significance.

Sugarcane grows as an annual crop, although in some areas a crop may 

require 18 months to mature. Growth of a crop is from vegetative stem cuttings.

Segments of a cane with three to five nodes, each with a bud, are placed in shallow

soil depressions. Buds rapidly grow up and roots down from the vegetative buds.

Depending on growing conditions, a grower may be able to get 2 to 10 crops from

one well-established rhizome in subsequent years. Planting may be by hand, but 

in developed countries it is mechanized. Herbicide and fertilizer applications will

accompany the planting process. Shortly after flowering, a crop matures and harvesting begins (fig. 38). Traditionally, the sugar harvest season in Puerto Rico runs

from late January to early summer. Usually, fire is employed to rid the plants of

leaves (chaff), leaving just standing canes. In less developed countries, cutting and

gathering may all be done manually and cane may be taken to a nearby mill via ox

carts or narrow gauge railroad (fig. 39). In the main growing areas of Puerto Rico,

ox carts and trains became rarely seen as most cane was taken to the mill by 

large trucks.

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In sugar mills, the canes are put on conveyors and crushed with large-fluted

metal rollers, the juice squeezed out, and the vegetative residue (bagasse) discarded. Bagasse can be used as a fuel supplement, as compost, or in paper production.

Cane juice requires removal of impurities by filtering and boiling. This produces a syrup which is heated, forming crystals. Centrifuges separate the crystals

from the remaining syrup. At the end, two products are produced—sugar crystals

and sugar molasses. Raw sugar (brown) has some impurities and a little molasses

in it. Refined sugar (granulated white) has the impurities removed. Molasses is

vital to the production of a variety of other products. Most importantly in Puerto

Rico, it is the basis for rum production. Rum is one of Puerto Rico’s main exports,

with the United States as the major importer. Bacardi is the number one brand of

hard alcohol consumed in the United States where 21 million cases are sold per

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38—View of sugarcane field in flower. 

G. Miller
year. All federal taxes collected on the sale of rum in the United States are returned

to Puerto Rico. This economic stimulus pumps over $250 million into Puerto

Rico’s economy.

Pineapples—

Scientific name—Anana comosus (L.) Merrill

Plant family—Bromeliaceae (Bromeliad family)

Growth form—Biennial rosette with a multiple fruit and armed leaves

Origin—South America

Domesticated—Prior to 1500

Historical significance—Throughout the world, pineapples are used as a symbol

of hospitality. They appear in the stone carvings of many public buildings, and their

likenesses are used in home decorations (bedposts, wallpaper, and fabric design).

Growth cycle—Pineapples (piña) belong to a unique family of plants, the 

Bromeliads. This is a family dominated by epiphytes, the so-called “air plants.”

Most of these plants grow on other plants, such as forest trees. Pineapples are

ground-dwelling bromeliads. Most cultivated forms of this plant are seedless,

reproduced by asexual cuttings. The upper leafy branch or axillary branches are

detached and planted. Plants grow as a cluster of spiny rosette, bayonet-shaped

leaves. The upper extensions of the stem will bear one- or two-flower stalks consisting of up to 200 individual flowers. Flowers, subtending bracts, and the flower

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Figure 39—Transport of sugarcane in preparation for milling was frequently done by ox carts. 

G. Miller
General Technical Report IITF-35

stalk all fuse together to form a complex multiple fleshy fruit (fig. 40). When the

fruit turns yellowish, it is ready to harvest. Today, fruit development and ripening

are controlled by spraying plant hormones or carbide gas onto the field at a precise

time in anticipation of when the fruit is to be shipped and served. It takes approximately 4 to 5 months for a mature fruit to develop. Commercial plantations replant

every 3 to 4 years because root death and diseases cause fruit size to decline.

Pineapple, locally known as piña, is one of the fruits everyone associates with 

the tropics. It is native to the Western Hemisphere and is thought to have been

domesticated by the Guarani people of present day Southern Brazil. By the time 

of Columbus’ second voyage in 1493, it had spread to the Caribbean where he

bartered for it in Guadeloupe.

It was taken back to Europe and spread to India by the mid 1500s and was

introduced to the East Indies shortly thereafter. It was initially grown for European

royalty. Royal English gardeners built special greenhouses for propagation and

selective improvement. By the late 1800s, the modern pineapple, and the subsequent development of the pineapple-growing industry, started in Hawaii, where

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Figure 40—The multiple fruit of a mature pineapple. 

G. Miller
today most of the U.S. commercial production occurs. Its common name is the

result of the fruit resembling the outward appearance of a pine cone, with a soft

fleshy center, like an apple.

Puerto Rico grows pineapples commercially on the north coast in the AreciboManatí area. It is the third most important crop on the island. Prior to expansion of

the autopista (toll road) in the area and commercial development along Highway 2,

there were large pineapple fields on both sides of the road. To see fields today, you

will have to exit off these roads. Many small farmers grow pineapples as a cash

crop and sell them from roadside stands throughout the island. Sweet, ready-to-eat,

field-ripened pineapples are especially abundant in the Cabo Rojo area where they

may grow to 9 kilos (20 pounds). They are generally much better quality than those

available in Puerto Rico’s supermarkets, because supermarkets often sell imported

pineapples that were harvested green. A description of the plant’s biology follows.

Pineapples grow best in light soils, with good drainage, and a pH around 6.5.

These soil conditions are found in the karst area of Puerto Rico’s north coast. As is

the case with sugarcane, many of the commercial pineapple fields are located in

areas undergoing rapid development (housing, strip malls, and transportation corridors), and as a result, the land values are ever on the increase. There are three varieties of pineapples grown, with cayenne and red Spanish being the two grown in

Puerto Rico. The cayenne variety has a smooth leaf, whereas the red Spanish

exhibits a spiny leaf. Pineapples are mostly known for their delicious, fleshy fruit.

Their juice is also widely consumed throughout the world. The fruit and juice contains bromelin, a digestive enzyme, often used in tenderizing meat. This crop

requires fertilizers and pesticides. Weed control is effectively accomplished by

growing plants in a black plastic soil cover. The main growth problems in Puerto

Rico are soil nematodes and bacterial wilt associated with wet soils.

Coffee—

Scientific name—Coffea arabica L. (90 percent of world production)—

(C. robusta and C. liberica—10 percent of world production)

Plant family—Rubiaceae (Madder family)

Growth form—Perennial shrub, small tree

Origin—Ethiopia

Domesticated—13th century in Arabian Peninsula (Yemen)

Historical significance—A major tradable commodity heavily controlled by 

Arab traders who sterilized all beans harvested so the beverage could not be grown

by other trading groups. Coffee was introduced by the Dutch into the New World

tropics in the 1720s.

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Growth cycle—Coffee (café) is now grown throughout the tropics (20o N and S 

of the equator). It frequently grows best in mountainous terrain, but can be grown

close to sea level. As was the case with sugarcane, this plant’s culture was very

labor intensive and gave rise to increased slave trade in the New World, but not in

Puerto Rico. It is a plant influenced by cold weather; thus wild price swings occur

as cold periods affect bean production in countries such as Colombia or Brazil. 

In northern Latin America, it is the leading source of foreign exchange.

Coffee “trees” are usually grown from seeds and planted into the field as young

shrubs (fig. 41). Individual trees will bear fruit at 3 to 5 years of age and can bear

harvestable fruit for 40 years (fig. 42). Mature plants typically produce 5 to 6

pounds (2 to 3 kilograms) of fruit per year. Approximately 2,000 beans are in a

pound ( less than 1 kilo) of coffee. One pound of coffee beans ready to roast will

require 5 to 6 pounds of freshly picked raw fruits. Because most plantations are

located in mountainous highlands, gathering of beans is done by hand. Mechanical

harvesting is possible on flat or gently rolling landscapes. Mechanized harvesters

do the equivalent work per day of 100 pickers. At the height of the harvest season,

pickers may be able to pick up to 200 pounds (10 kilograms) per day.

144

Figure 41—The leaves, flowers, and fruits of Coffea arabica L.

(coffee).
Traditional coffee cultivation is best in frost-free areas, receiving 1500 to 2500

millimeters (60 to 100 inches) of rainfall, and growing in a shaded environment.

Coffee is frequently grown in an agroforestry setting with a variety of other fruit

and vegetable species in the same system. Coffee grows best in fertile, well-drained

soils. The major pest of coffee is the coffee leaf rust (Hemileia vastatrix) that, 

once introduced, is very difficult to control, so coffee is grown in areas free of 

the rust. Ceylon lost its entire coffee-growing area to the rust in the late 1800s.

Unfortunately, the rust was introduced into Brazil in 1970 and Central America 

in 1976 (Perfecto et al. 1996).

Recently, many coffee-growing regions have started to switch to sun-loving

trees, which produce slightly larger yields, but have shorter life expectancy. This

switch has serious ecosystem and watershed implications, as it requires all canopy

tree species to be eliminated, which results in a serious decline in the complex

agroecosystems that serve as vital wildlife habitat. The implications of this change

to a true coffee monoculture are discussed in the section on Neotropical migrants.

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Figure 42—Closeup view of the leaves, flowers, and fruits of

coffee. 

G. Miller
General Technical Report IITF-35

By 1990, half of the 2.7 million hectares (6.7 million acres) of coffee plantations 

in northern Latin America had already been converted to high-yield sun plantations.

Sun-grown coffee is considerably more expensive to produce than traditional

shade-grown coffee. However, owing to environmental problems and shorter tree

lifespans—which requires expensive replanting—many farmers are returning to

shade coffee plantations.

Once the coffee berries are picked, they are depulped (fruit wall and seedcoat

removed) and the two beans per fruit (mostly food storage/endosperm) are gathered

en masse and dried. Once dry, the beans are roasted. Roasting is critical because it

imparts the aroma and flavor to the finished coffee. Both temperature (184 to 188

oC or [392 to 400 oF]), and time (5 to 15 minutes) of roasting, are critical to chemical reactions involving starch, sugars, and caffeine that take place as the bean is

roasted. 

At the end, a once light green bean is now dark brown to black, and a specific

aroma and taste is imparted as the coffee is ground and brewed in water. Espresso

coffee involves forcing steam through deep dark-roasted ground coffee. Espresso

bars are very common in Europe and throughout Latin America. Americans tend to

prefer light or medium roasted and less strong coffee. Many Puerto Ricans drink

café con leche, an equal mix of boiled milk and dark roasted coffee. Either type of

coffee contains 1.5 percent caffeine. Decaffeinated coffee has the caffeine removed

by solvent extraction prior to roasting. The caffeine is then crystallized and sold as

a food additive in soft drinks, and in headache and cold medicines. Twenty percent

of U.S. coffee consumed is decaffeinated. 

Coffee is an important beverage to many people in the world. It is the most

important beverage commodity imported into the United States and one of the most

important commodities traded internationally, ranked second after oil. Coffee is

consumed most heavily in the United States (330 million cups per day). Nearly 50

percent of the world’s coffee beans are purchased by three American multinationals

(Kraft, Sara Lee, and Proctor and Gamble) and the Swiss food giant, Nestlé. More

than 50 percent of the U.S. population drinks coffee. The U.S. coffee industry is

worth an estimated $18 billion per year based on the 2.4 billion pounds of coffee

that are imported. It is also heavily consumed in countries of Western Europe and

throughout the tropical Americas. It was once the beverage of aristocrats, but today

is the preferred morning and after-dinner beverage of people the world over. Coffee

comes from a tropical shrub (small tree) with its center of origin in the highlands of

east Africa. Today, most of the world’s coffee production is grown in Colombia and

Brazil. There are 80 countries in the tropics that grow coffee for export and their

146
own domestic consumption. More than 25 million people are employed around the

world in this $50 billion industry. Table 17 shows the approximate size of coffeegrowing area by country or region in northern Latin America. In 2002, 117 million

bags of coffee weighing 60 kilograms (132 pounds) each were harvested worldwide.

Puerto Rico still has many small coffee plantations centered in the Cordillera

Central Mountains. There are 20 coffee-producing municipalities in Puerto Rico.

One of the coffee-growing areas near Adjuntas convinced the Puerto Rico government to create a new national Park—El Bosque del Pueblo (people’s forest) to save

one of the best coffee-growing areas from strip mining for copper and other metals

(Gómez 2001). Many small plantations can be accessed along Route 10 as one

travels north from Ponce to Arecibo. Throughout the mountains, there will be plantations in full flower (white), while others will be exhibiting ripe red fruits (cherries). Naturally sun-dried beans are often seen lying along the road on burlap cloth.

Many roadside stands and all community produce markets will have locally grown

beans for sale. Puerto Rico has a series of island brands available as beans, ground,

or instant coffee. All are very good, and one brand is notable because it is referred

to as “the coffee of the popes” and has been a staple beverage in the Vatican for

years. Pope Leo XIII designated Puerto Rican coffee an excellent drink. Unfortunately, Puerto Rico’s great coffee exporting period ended in 1899 when Hurricane

San Ciriaco severely damaged coffee plantations throughout the island. Shortly

thereafter the United States barred Puerto Rico from conducting foreign trade; thus,

the export of one of its most profitable products went into steep decline from which

it never recovered (see app. 2).

In the United States, coffee is frequently used as a loss leader by large food

chains in order to attract customers. Thus, on the same shelf, the customer may see

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Table 17—Approximate area of coffee production by country or 

region in northern Latin America 

Percentage

Country/region Area in sun coffeea

Hectares (acres)

Colombia 1 million (2.47 million) > 60

Central America 750 000 (1.85 million) > 20

Mexico 700 000 (1.73 million) 15

Caribbean countries 300 000 (741 thousand) < 5

Totals 2.7 millionb (6.79 million)

a Data for percentage in sun coffee are 1990 estimates.

b 7 percent of usable land and 44 percent of total area of permanent cropland.

Source: Modified from Perfecto et al. 1996.
General Technical Report IITF-35

prices vary from $0.99 to $13.99 for the same quantity of coffee offered under 

different brand names. Today, specialty coffee labels and coffee restaurants dedicated to a wide array of coffee-based beverages are available. Dozens of adulterants,

additives, and flavor enhancers are added to coffee to produce the current trend 

of designer coffees now available at specialty coffee houses. A fresh 6-oz cup of

coffee may range from $0.69 to $6.00 on the same city street in the United States

depending on who is selling it and what additives are in it. Good old-fashioned 

regular is usually the truest in terms of taste and cheapest in price. 

In Puerto Rico, fresh coffee is frequently sold as café con leche or pocillo (a

pocillo is a demitasse of coffee). Many visitors to Puerto Rico enjoy local brands

and often take bags of island coffee products home to share with family or to give

as gifts. Any large food store will have a complete array of local brands.

Bananas—

Scientific name—Musa paradisiaca L. (plus numerous other cultivars 

and species)

Plant family—Musaceae (Banana family)

Growth form—Upright herbs that appear tree-like; up to 10 meters tall 

(33 feet)

Origin—India

Domesticated—India and other Asiatic countries for at least 2,500 years; introduced into the Caribbean early in the 16th century.

Historical significance—Bananas are important economically throughout the 

tropical world, especially in Central America where most countries were referred to

as “Banana Republics” owing to intertwining of bananas, economies, the military,

and large U.S. fruit companies (Jenkins 2000).

Growth cycle—Annual herb that can resprout yearly from rhizomes.

Bananas (guineo) are the United State’s number one snack or dessert fresh 

fruit. Interestingly, prior to the 1880s, bananas were largely unknown in the United

States, but by 1910 they were common. The United States imports more bananas

than any other country, and United States fruit companies early in the 20th century

had enormous influence on most Central American and a few northern South

American countries and transport systems. Large areas of land are still controlled

by Dole, United Fruit, and others, in Ecuador, Colombia, Costa Rica, Panamá, El

Salvador, and Guatemala. Today, Ecuador is the largest exporter of dessert bananas,

with most destined for the United States. Bananas trail only grapes, citrus, and

apples as the fourth largest fresh fruit crop of the world. It is the developing

world’s fourth most important food crop.

148
Banana trees (a woody plant is considered a tree when it exceeds 15 feet in

height) are among the plants people conjure up in their minds when they think of

the tropics. They are interesting plants in that they are the world’s largest herb,

achieving heights of 10 meters (33 feet). They are easily grown and typically 

produce a crop of fruit yearly.

Throughout Puerto Rico, bananas are grown both commercially and by individual families for their own consumption. Banana trees can be seen throughout the

island, except in the most wet and dry areas. With the decline of sugarcane in the

coastal plain, some of these lands are now being converted to commercial banana

plantations. Most homeowners with a yard will likely have a couple of trees around

their home for family consumption and decoration. Bananas in Puerto Rico are

mostly eaten unripe and boiled.

The banana requires hot and humid conditions found in the tropical and subtropical latitudes. It is native to the Indo-Malaysian region where it was domesticated 3,500 years ago or more. The word banan is Arabic for finger and so applied

to the fruit because of its shape. Bananas reproduce vegetatively via sucker sprouts

from an underground rhizome (horizontal stem). The small brown seeds seen in a

banana fruit are aborted because they are the result of triploidy (three sets of chromosomes), which interferes with normal development of the embryo. Thus, all

plants derived from the same individual are clones and genetically identical. There

are thought to be over 300 cultivars of Musa now in production throughout the

tropical world. These clonal types have varied features relative to taste quality, 

texture, size, and color of the fruit, resistance to disease, and tree height.

As a bud develops off the rhizome, it grows aerially into what appears to be a

tree trunk. In actuality, that trunk is a tightly wrapped group of leaf sheaths and is

not woody. As it develops through the annual cycle, more and more leaves emerge

from the center of the sheath and the blade expands out after emergence. The leaf

blades are quite large, up to 1 by 3.66 meters (3 by 12 feet), oval, and when young,

entire. Owing to weather conditions, most banana leaves will split into the mid vein

throughout the blade. The leaves are frequently used in various aspects of food

preparation and storage in the tropics.

Late in the annual cycle following development of the vegetative tree, the 

apical meristem converts to a flowering meristem and a large single inflorescence

emerges out of the rosette of leaves. Along the flowering stalk a series of flower

rows will emerge forming the so-called hands of bananas as they grow. Each row

will initially be covered by a brilliant purple-pink bract, thus, banana flowers are

large and colorful (fig. 43). The banana flower is perfect in that both male and

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female parts are present, but it is the pistillate (female) flowers that develop into

individual banana fruits parthenocarpically, that is, asexually. Banana fruits are a

modified berry and mature in 3 to 5 months. Bananas for direct consumption are

normally tree ripened. Commercial bananas are packed green and shipped around

the world in refrigerated container ships where relative humidity is controlled at 

90 percent and the temperature is 13 oC (mid 50s oF). Bananas can be artificially

ripened by applying ethylene gas. Once ripe, the useful shelf life of bananas is only

a few days.

After fruit harvest, the tree is chopped down and either replanted via new 

suckers, or a new sprout from the previous rhizome will be allowed to grow.

Throughout the process, fertilizers and pesticides are used to promote growth, 

control fungal wilt, and reduce loss by fungal infection in transit. Under good

growing conditions, carbohydrate yields are similar to the yields of potatoes in the

temperate zone. Each year, great losses of banana crops occur as a result of hurricanes and typhoons throughout the tropics. The economies and governments of

some countries rise and fall based on storm frequency.

Bananas were introduced to Africa by Arab traders; then Spanish and

Portuguese traders spread them to the Neotropics, the center of world production 

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Figure 43—Banana tree with maturing inflorescence.

G. Miller
of sweet bananas. Plantains, which are large, starchy, and not sweet, are commercially cultivated for world distribution largely in Africa. The plantain banana is a

true staple and major supplier of carbohydrates throughout much of the tropics.

They are similar to the Irish potato in the diets of people from temperate lands.

Plantains are eaten more frequently in a variety of forms on a daily basis than are

sweet bananas. They can be boiled, baked, and fried. All are good sources of energy and potassium. In Puerto Rico, one of the most common ways to prepare them

is as tostones. Here, the plantain is sliced, pounded with a mallet, and deep fried.

They are frequently served as a vegetable side dish when eaten at a restaurant.

Today, bananas are also chipped and sold as a snack food like potato chips are in

the United States. When there are excess bananas, they are frequently used as animal feed, whereby the entire banana is consumed.

In most banana-producing countries, there is great concern about the ecological and health implications of the use of pesticides. In many cases, pesticides are

applied by men wearing swimming suits and plastic open-toed shoes; thus, by the

end of the day they are covered in pesticides. Many communities exhibit high 

incidences of still births, malformed infants, and male sterility. Large plantations

usually apply their pesticides via spray planes resulting in offsite migration of the

chemicals. Frequently, these plantations are bordered by squatter communities. In

addition, local water supplies may become contaminated with residues. There are

lawsuits pending in some countries related to these issues.

In July 2001, it was announced that an international research consortium

(Global Musa Geonomics Consortium) would attempt to sequence the entire

banana genome by 2006 to isolate and develop disease-resistant bananas. One 

disease, black sigatoka caused by Mycosphaerella fijiensis fungus, is known to

have devastating effects and can reduce yields by 50 percent. The bananas’ genome

is 500 to 600 million base pairs and represents the largest plant genome to be

attempted thus far (Gewolb 2001).

Citrus—

Scientific name—Citrus spp. (C. sinensis (L.) Osbeck (sweet orange), 

C. aurantifolia (L.) Swingle (lime), C. limon (L.) Burm. (lemon), 

C. paradisi Macfayden (grapefruit), and numerous other species)

Plant family—Rutaceae (Citrus family)

Growth form—Tree

Origin—Southeast Asia (China to Australia)

Domesticated—Well before Greek and Roman times, probably in China 

and India

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Historical significance—Citrus was brought to the New World by the Portuguese 

and Spanish. It was important to the health of sailors in preventing scurvy. English

sailors were called “Limeys” because they carried fresh limes and kegs of lime

juice on long voyages.

Growth cycle—Orange trees are easily grown from seeds, and trees will grow to 

10 meters (33 feet) in height. They have broad evergreen leaves that are ovate, with

winged petioles, and fragrant, white flowers (fig. 44). Growth can take place in a

variety of soils from sandy to clay loams, but they prefer well-drained soils. Most

new orchards result from small orange trees that are budded on stocks grown from

the seed of specially-selected trees, having spent 1 year in a greenhouse and another year in a nursery. Profitable fruit production occurs at about age 6 to 8. Mature

trees will bear fruit for about 80 years and, in some cases, centuries if free of disease and weather-related damage. The orange crop is normally picked when ripe

(fig. 45). About 40 percent of the U.S. orange crop is made into frozen concentrate.

Many fruit farmers in the U.S. have two chronic problems to deal with, one is

threat of frost and the other is the rise in land values in the sunbelt states. To keep

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Figure 44—The leaves, flowers, and fruits of Citrus sinensis (L.)

Osbeck (orange tree).
up with the ever-increasing demand, the industry had to go south into the tropics

where cheap land was available.

Citrus fruits are among the most enjoyable products directly consumable from

nature. Their original distribution was primarily the southeast Asian tropics, but

today they are grown throughout the tropical world and throughout the southern

tier states of the United States, with Florida and California being the major producer states. It is the number one tree fruit crop in the United States. There are a number of species that produce edible fruits, with four of them very common to Puerto

Rico. Citrus can be seen throughout the island, including the dry areas of the southwest and the wet areas of the Luquillo Mountains. There are no extensive groves as

you would see in Florida or California; instead they will more likely be 1 to 2 acres

and frequently associated with other agroforestry species. Most people with yards

are likely to have one or more of these species growing around their homes for 

personal use.

Citrus has become a huge commercial endeavor, and many U.S. fruit companies have established large holdings in Mexico, Brazil, and other tropical countries.

Today, orange juice (jugo de china, as it is called in Puerto Rico) is frequently a

mixture of juices originating in two or three countries.

The fruit of an orange tree is a modified berry called a hesperidium. The skin is

full of aromatic glands and oils, as are the leaves. The oils are also a major product

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Figure 45—Sweet orange tree in the mountains of Puerto Rico. 

G. Miller
General Technical Report IITF-35

used in the cosmetics and perfume industry. Most oranges produce viable seed and

are easily grown from seed. Navel oranges are seedless, and it is thought that the

southern California navel orange industry is based on two asexually propagated

trees introduced in the early 1870s. The fleshy part of the fruit is divided into a

series of sections filled with modified juice-bearing hairs, which we squeeze for

juice or eat directly. Sweet oranges contain about 10 percent sugar in their juice.

Pulp left over from processing can be used as an animal food, soil amendment, or

in a variety of industrial products such as beverage flavoring, cleaning products,

and medicinal additives. Orange juice is part of most American breakfasts, and

grapefruits are likely to be on the menu for most dieters. Citrus is an excellent

source of vitamin C and beta-carotene. Today, many commercial juices are also 

fortified with calcium and vitamins D, E, and C, as well as zinc.

Citrus was introduced into Puerto Rico in the early 1500s. Most of Puerto

Rico’s citrus is grown for local fresh consumption. In fact, most frozen orange

juice in food stores is imported from Florida. Fresh oranges (locally called chinas)

are available year round from roadside stands and street venders. For $3.00, you

can buy 10 to 15 oranges (depending upon size). These are tree-ripened fruits and

wonderful for sweet juice production. When buying fresh fruits, do not expect the

perfect orange color typical of the American supermarket. Oranges from large commercial groves in the United States may be color processed and gassed with ethylene, which causes chlorophyll breakdown. Locally grown oranges in Puerto Rico

are likely to be somewhat green. Some venders may not wash their fruits and they

may have blackened areas as a result of microepiphytes growing on the fruits.

These are easily washed off and do not present a health hazard.

Mangoes—

Scientific name—Mangifera indica L.

Common name—Mango

Family name—Anacardiaceae (Cashew family)

Growth form—Tree

Domesticated—Ancient period, southeast Asia

Historical significance—Mangoes were introduced to the West Indies from South 

America in the mid 1700s.

Growth cycle—Mango trees can grow to 23 meters (75 feet) tall; they have a broad

canopy, with large, evergreen, lance-shaped, simple leaves. The flowers are a terminal complex inflorescence called a panicle. Flowers vary in color from greenyellow to purple-pink. Although many individual flowers are produced, generally

154
only one yellow elliptic fruit develops from each panicle. It is a large aromatic fruit

called a drupe, with one seed (fig. 46). They are frequently planted as shade trees

around homes. The largest mango tree in Puerto Rico, located in Arecibo, is 36.9

meters (121 feet) tall, with a crown spread of 18.9 meters (62 feet) and a circumference of 6.4 meters (20.9 feet).

Mangoes are ancient fruits found originally in a broad area of Southeast Asia.

They belong to the same family as poison ivy and poison sumac, common plants 

in the Eastern United States that produce skin reactions in the form of dermatitis. 

In Puerto Rico, the two common poison plants of the genus Comocladia are also

members of the Anacardiaceae family. Some people are also allergic to mango pulp

and juice, especially if the fruit has not fully ripened. If you are allergic to poison

ivy, be careful to take in only small quantities of the mango fruit. Some individuals

will have gum, tongue, and throat reactions. Be sure to peel the fruit, as most allergic reactions are from contact with the latex in the skin.

Mangoes are very common trees throughout Puerto Rico, introduced via South

America around 1750. Today, mangoes are extremely common along virtually all

roads on the island because once the fruit is consumed, the large seed is generally

thrown out the window of the vehicle or near someone’s residence. In other cases,

they were vectored by animals that ate the fruit and deposited the seeds randomly.

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Figure 46—The leaf, flowers, and fruits of Mangifera indica L. (mango tree).
General Technical Report IITF-35

Mangoes typically flower in the “winter” in Puerto Rico, but flowering is variable from November to July, with fruits maturing May to September. Mangoes are

a favorite fruit of many residents of the tropics and most homes have one or more

trees in their yards. They are also grown commercially in small groves as a cash

crop, often in combination with other fruit trees or shrubs. The flesh of the fruit is

juicy and somewhat fibrous and is normally eaten fresh. It can be canned, pickled,

or juiced. In the tropics, mangoes are as popular a fruit as apples in the temperate

zone. Improved commercial varieties are sweeter, juicier, and less fibrous. Mangoes

have carotenoids and possible anticancer properties. Mangoes are now sold widely

in health food stores throughout the United States. They are heavily exported

worldwide today and often used as a loss leader in the produce section of many

U.S. supermarkets. Processed pulp residues can be used for animal feed, and 

seeds can be ground and used as flour. Mango fruits and leaves are important 

decorations in eastern cultures. The wood has a variety of uses from furniture, 

to box construction.

Many other tropical edible plants could have been selected for description, 

but these are species likely to be seen throughout Puerto Rico. Many more tropical

agricultural products can be found at regional produce markets (See app. 2).

For additional reading see Franco et al. 1997, Gómez 2001, Jansen 1973,

Leakey and Wills 1977, Levetin and McMahon 1999, Little and Wadsworth 1964,

Parrotta 1993, Royal Botanical Gardens Kew 1998, Schery 1975, Simpson and

Ogorzaly 1995, U.S. Department of Commerce 1972, and Wadsworth 1997.

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Continue
Chapter 4: Freshwater Wetlands and

Coastal Ecosystems

Wetland Ecosystems

Puerto Rico has a variety of freshwater and marine wetland ecosystems that range 

from the seagrass and mangrove ecosystems on the coast, to hundreds of wetlands

associated with freshwater rivers and lakes, and even the wetland cloud forests high

in the Luquillo Mountains.

What is a wetland? Wetlands are viewed as transitional areas between aquatic

and terrestrial systems. According to Mitch and Gosselink (1993), wetlands are

areas that exhibit certain distinguishing characteristics such as continuous or periodic presence of standing water, unique wetland soils, saturated soils, and vegetation adapted to or tolerant of saturated soils. Wetlands are not necessarily easily

defined because they have a considerable range of hydrologic conditions and

because they are found along a transitional gradient between upland (nonwetland)

systems or deep water systems such as lakes and the ocean. Swamps, marshes,

and bogs all fit the description of a wetland.

Wetlands in Puerto Rico are among this planet’s most biologically productive

ecosystems (fig. 47). Wetlands associated with montane rain forests in Puerto Rico

contain rare plant and animal species and are species-rich (Lugo and Brown 1988).

Runoff from these same mountains provides public water resources for human

communities downstream. Once that water reaches the coast, it helps form critically important riverine, coastal marine, and estuarine wetland ecosystems (mangrove swamps, seagrass beds, and coral reefs). These are essential breeding and

nursery habitats for many fish, crustaceans, and many other plants and animals in

the complex food webs to be described later. Thus, there is a wetlands continuum

that starts in the tops of the highest mountains and continues all the way through

the coastal zone. A variety of organisms are tied to this aquatic continuum. Some 

of the species in mountain streams migrate to the ocean for reproduction and then

migrate back upstream. They are called catadromous species. An example is the

freshwater decapod (shrimp) that lives as an adult in the mountain streams. Its 

larvae float downstream and develop in the estuaries and ocean of the coast. Small

shrimps then migrate in great numbers, usually at night, back up the mountain

stream for their adult phase. 

Figures 48 and 49 illustrate this wetland zonation continuum. Puerto Rican

coastal wetlands are highly valuable wildlife habitats, such as those found at Cabo

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Figure 47—Relative productivity of wetland ecosystems in relation to others. From Newton, 1981.
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Figure 48—

Generalized geohydrologic setting of wetlands in Puerto Rico. Wetland types from

Lugo and Brown, 1988.
General Technical Report IITF-35

160

Figure 49—Profile diagrams of representative wetland ecosystems in Caribbean islands.
Rojo National Wildlife Refuge, the Laguna Cartagena National Wildlife Refuge,

and the Laguna Tortuguero National Reserve (see app. 2 p. 376).

Throughout Puerto Rico’s agricultural expansion period, wetland ecosystems

were heavily degraded and destroyed as a result of dredging, filling, draining,

eutrophication, and use of agricultural fertilizers and pesticides. Unfortunately, no

one knows what the original freshwater wetlands coverage was in Puerto Rico at

the time of Columbus. There is no realistic set of statistics available to compare

current trends in wetland loss or growth in Puerto Rico. To give some perspective

to wetland loss, in the continental United States, less than 50 percent of the original

wetlands coverage remains today. In Puerto Rico, one low-elevation freshwater

coastal swamp forest type dominated by Pterocarpus officinalis Jacq.1 (swamp

bloodwood, box 19) is quite rare today (243 hectares or 600 acres). It probably

occupies no more than 5 percent of its original range making it deserving of special

protection status. As a result of being a coastal plain ecosystem, the pterocarpus

swamp has been reduced to only a few small remnant stands. The rest fell prey to

coastal development and agriculture. Mangrove forests and palustrine freshwater

wetlands continue to be at-risk wetland types throughout Puerto Rico.

With cessation of many agricultural activities throughout Puerto Rico, wetlands

are starting to redevelop. Part of this unexpected ecological response is related to

increases in the abundance of freshwater runoff to coastal areas as a result of reduced

usage of water by agriculture for irrigation, and abandonment of maintenance of

drainage canals. As a result, freshwater wetlands in the coastal zone are increasing

in area. Figure 50 represents the current distribution of wetlands in Puerto Rico.

Wetlands serve many functions in nature, and humans derive many benefits

from these special ecosystems. The following list identifies some of the values of

wetlands, all of which apply to Puerto Rico’s wetlands.

➢ Flood conveyance ➢ Water supply

➢ Barriers to waves and erosion ➢ Food production

➢ Floodwater storage ➢ Timber production

➢ Sediment control ➢ Education/research

➢ Fish and shellfish nursery ➢ Open space

➢ Habitat for waterfowl and wildlife ➢ Aesthetics

➢ Habitat for rare and endangered species ➢ Enhanced water quality

➢ Recreation

Wetlands are classified into the following types, according to their position on 

the landscape and their attributes. At times, wetlands are discrete ecological units

and yet, in many instances, they are highly interrelated (fig. 51):

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1 See appendix 1 for Common and Latin names.
General Technical Report IITF-35

Box 19. Pterocarpus officinalis Jacq. (swamp bloodwood)

This tree is an indicator species for 

a rare habitat in Puerto Rico, the 

freshwater swamp. A swamp is a 

wetland dominated by woody plants

(trees and shrubs). Swamps exhibit 

full or periodic wet soil conditions.

Pterocarpus officinalis can grow in

areas that are slightly brackish and

sometimes grows as a natural monoculture in habitats with sizeable yearly

water fluctuations. At one point, this

tree may have exhibited extensive 

coverage in wet areas of the coastal 

plain, but today its habitat and species 

coverage is greatly reduced, possibly to as little as 5 percent of its original

coverage. Its greatest loss is thought to have resulted from land clearing for

agriculture, especially for growing sugarcane, and more recently, resorts and

golf courses. Swamp bloodwood exhibits a disjunct distribution pattern

because there are small populations of this tree in stream borders in the mountains of the Caribbean National Forest. A more complete review of wetland

types, their values, and problems in their maintenance is presented in the 

section on wetlands.

This tree is a Neotropical species ranging from southern Mexico to northern South America, the Greater Antilles, and much of the Lesser Antilles in

coastal and interior swamp forests. As a result, it has many common names

throughout its large geographic area. It is an evergreen species with alternately

arranged, pinnately compound leaves. The oblong leaflets vary from five to

nine. A pair of stipules subtend the petioles. Its yellow flowers form a raceme

and are typical of the pea family in shape. Its pod-like legume fruits are round,

dark brown, winged at maturity and measure 3.75 to 5 centimeters (1.5 to 2

inches) in diameter. Flowers form February through September, and fruits

develop April to November. It can regenerate via root sprouting should it be

damaged by hurricanes or cutting. The fruits float when released, and water

and hurricanes may be the primary dispersal agents. Trunks are frequently buttressed and curved, almost snake-like, on the swamp floor. Its bark is smooth

to lightly fissured and light brown. The inner bark is blood red, thus the name

bloodwood.

162

The leaves, stems, flowers, and fruit of

Pterocarpus officinalis Jacq. (Swamp bloodwood)
Box 19. continued

Bloodwood 

sapwood is yellowwhite, lightweight,

and weak, thus it

has little commercial value except 

for items such as

fishnet floats. Its

resins are used for

medicinals such as

astringents. It can 

be used as a shade

ornamental, especially in moist areas. It can grow into a sizeable tree achieving heights of 40

meters (130 feet) and have diameters up to 90 centimeters (36 inches) above

its buttressed lower trunk. Some buttresses can rise 4.5 meters (15 feet) off the

swamp floor. It also produces pneumatophores at the ends of buttress development, which aid in gas exchange. 

The largest swamp bloodwood in Puerto Rico is located in Luquillo and is

8.6 meters (28.2 feet) in circumference, stands 20.5 meters (67 feet) tall, and

has a crown spread of 6.9 meters (22.6 feet). Most bloodwood species are

much smaller than this record individual. Because it produces lightweight

wood, it probably grows fast. Interestingly, this tree hosts lots of epiphytes,

one of which is particularly noteworthy: Psilotum nudum (L.) Beauv. (wiskfern). This is one of the most primitive and ancient of tracheophyte plants on

Earth as most of its closest relatives are known only from the fossil record.

In review, bloodwood exhibits a series of adaptations for survival under

wetland conditions, which include:

➢ Ability to grow under a variety of flood conditions

➢ Rapid growth rate

➢ Ability to sprout when damaged

➢ Production of pneumatophores for gas exchange

➢ Buttressed trunk growth for support

➢ Tolerance to brackish conditions

➢ Seeds that float

For more information on this species, see Álvarez López 1990, Little and 

Wadsworth 1964, and Weaver 1997.

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Bloodwood trees in Pterocarpus forest near Humacao, Puerto Rico. 

A.E. Lugo
General Technical Report IITF-35

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Figure 50—

Current wetlands distribution in Puerto Rico.
Palustrine—All nontidal and tidal freshwater wetlands dominated by trees, shrubs,

persistent emergents, and/or submerged aquatic plants—for example, marshes,

bogs, and swamps. These are shoreward of lakes, rivers, estuaries, or islands in

rivers and lakes and wet depressions (fig. 52).

Lacustrine—Permanently flooded lakes, ponds, and reservoirs greater than 8.1 

hectares (20 acres) and deeper than 2 meters (6.6 feet). Vegetation is largely emergent and/or submergent/floating plants.

Riverine—Channelized wetlands bounded by riverbanks or human-made levees, 

or where persistent emergents, and/or submergent plants are present.

Estuarine—Tidal habitats and adjacent areas such as bays, sounds, and lagoons 

where salinity of the water is >0.5 parts per thousand.

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Figure 51—Diagram showing major wetland habitat systems.
General Technical Report IITF-35

Marine—Extends from the outer edge of the island shelf to the high-tide mark on 

coastal beaches or where trees and shrubs extend to that part of the sea where the

water’s salinity is greater than 30 parts per thousand.

Plants typical of wetland habitats are generally adapted to the soil and moisture

conditions found there. The following types of plants are found in the wetlands of

Puerto Rico.

Submergent vegetation—Rooted or fixed plants, completely or largely submerged, 

such as:

➢ Potamogeton nodosus Poiret. (pondweeds)

➢ Hydrilla verticillata (L. f.) Royle (water hydrilla)

➢ Thalassia testudinum Konig (turtle grass)

➢ Najas marina L. (water naiad)

Free-floating vegetation—Unattached, floating, such as:

➢ Lemna perpusilla Torr. (duckweed)

➢ Azolla caroliniana Willd. (water fern)

➢ Eichhornia crassipes (Mart.) Solms (water hyacinth)

➢ Pistia stratiotes L. (water lettuce)

➢ Utricularia gibba L. (bladderworts)

Floating attached vegetation—Floating leaves, with attachments to bottom 

sediments, such as:

➢ Nymphaea odorata Ait. (white water lily)

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Figure 52—Typical cross section of a pond, lake, or marsh.
Emergent vegetation—Rooted plants with their principal photosynthetic surfaces

above the water, such as:

➢ Typha angustifolia L. (cattail)

➢ Phragmites australis (Cav.) Trin. ex Steud. (reed)

➢ Sagittaria lancifolia L. (arrowhead)

➢ Cladium jamaicense Crantz (sawgrass)

Woody plants—Trees and shrubs that can withstand water exposure to trunks 

and/or roots during periods of inundation, and soil conditions with reduced oxygen

availability include:

➢ Pterocarpus officinalis Jacq. (swamp bloodwood)

➢ Rhizophora mangle L. (red mangrove)

➢ Avicennia germinans L. (black mangrove)

➢ Laguncularia racemosa (L.) Gaertn. (white mangrove)

➢ Prestoea montana (Graham) Nichols. (sierra palm)

➢ Cyrilla racemiflora L. (palo colorado)

Some wetland plant species have very close relationships to soil and water 

conditions found in wetlands, so much so that they are not found elsewhere; whereas other plants are never found in wetlands. Following are indicator categories for

wetland plant species.

Obligate wetland—Species almost always found in a wetland under natural conditions (more than 99 percent probability), such as:

➢ Typha angustifolia L. (cattail)

➢ Eichhornia crassipes (Mart.) Solms (water hyacinth)

➢ Thalassia testudinum Konig (turtle grass)

➢ Rhizophora mangle L. (red mangrove)

Facultative wetland—Species that usually occur in a wetland, but are occasionally 

found in nonwetland habitat (67 to 99 percent probability), such as:

➢ Boehmeria cylindrica (L.) Swartz (false nettle)

➢ Bucida buceras L. (ucar)

➢ Cyrilla racemiflora L. (palo colorado)

➢ Prestoea montana (Graham) Nichols. (sierra palm)

Facultative—Species that are likely to occur in wetlands or nonwetlands habitat 

(34 to 66 percent probability), such as:

➢ Myrica cerifera L. (bayberry)

➢ Cakile lanceolata (Willd.) O.E. Schulz (sea rocket)

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Facultative upland—Species that usually occur in nonwetland habitat (67 to 99 

percent probability), such as:

➢ Casuarina equisetifolia L. (Australian pine)

➢ Cocos nucifera L. (coconut palm)

➢ Andropogon gerardii Vitman (broomstraw)

Obligate upland—Species that almost always occur in nonwetlands habitat (more 

than 99 percent probability), such as:

➢ Clusia rosea Jacq. (autograph tree)

➢ Colubrina arborescens (Mill.) Sarg. (coffee colubrina)

➢ Mangifera indica L. (mango)

Nonwetland—Species that never occur in wetlands, such as:

➢ Cephalocereus royenii (L.) Britton & Rose (pipe organ cactus)

To determine which category a species in Puerto Rico falls into, see the 

National Wetland Plant List (Reed 1988).

Most of Puerto Rico’s wetlands are estuarine and palustrine. The most common

wetlands on the island are described below.

Palustrine forested swamps—These are characterized by having more than 40 percent of the area in tree cover. They are situated in areas where they are occasionally

inundated by freshwater as exemplified by the Pterocarpus officinalis Jacq.

(swamp bloodwood) forests found at Dorado and Humacao and the high-elevation

palo colorado and palm forests where Cyrilla racemiflora L. (palo colorado) and

Prestoea montana (Graham) Nichols. (sierra palm) are the dominants.

Palustrine emergent marshes—These are dominated by herbaceous plants (25 percent or more cover) and woody plants (up to 40 percent cover). The freshwater

inundation in these areas varies from occasionally to regularly with typical species.

As exemplified by Cladium jamaicense Crantz (sawgrass) and Typha domingensis

Pers. (cattail) found in marshes at Tortuguero Lagoon. Palustrine marshes are common throughout Puerto Rico. More freshwater marshes are found on the north coast

of Puerto Rico owing to higher rainfall amounts and a more extensive river system.

Palustrine aquatic beds—These wetland areas are associated with freshwater 

rivers, lakes, and ponds. The aquatic beds will exhibit floating and/or submerged

attached vegetation in an inundated habitat such as at Tortuguero Lagoon and

Cartagena Lagoon. Plants such as Lemna perpusilla Torr. (duckweed), Nymphaea

odorata Ait. (white water lily), Eichhornia crassipes (Mart.) Solms (water

hyacinth), Pistia stratiotes L. (water lettuce), Potamogeton nodosus Poiret

(pondweed), and Utricularia gibba L. (bladderworts) can be present.

168
Estuarine forested/shrub swamps—These swamps are found along the coast 

where there are tides, currents, and storm surges that expose the habitats to salty

conditions as exemplified by the coastal forests dominated by Rhizophora mangle

L. (red mangrove) and Avicennia germinans L. (black mangrove). Saltwater

swamps can be seen in many areas of Puerto Rico, but particularly easy access is

available at Piñones, Boquerón, Guánica, and Aguirre. Commonwealth forest cover

can be up to 100 percent mangrove species. The lower reaches of Puerto Rico’s

rivers are estuaries where fresh and seawater mix. Saltwater can flow upstream in

these rivers as far as several kilometers. This explains why mangroves extend kilometers (miles) inland on the north coast of the island. They grow as far as the presence of saltwater occurs. Mangroves are the most extensive estuarine forested 

wetlands. The largest is just east of San Juan in the municipality of Carolina and

Loíza.

Estuarine emergent marshes—These coastal marsh wetlands are dominated by 

herbaceous plants (25 percent or more cover) and woody plants (up to 40 percent

cover). They are inundated at different frequencies and intensities by saltwater 

and will have species such as Acrostichum aureum L. (mangrove fern), Cladium

jamaicense Crantz (sawgrass), Typha domingensis Pers. (southern cattail), and

Laguncularia racemosa (L.) Gaertn. (white mangrove) present. These wetlands 

are located in areas to the rear of coastal mangrove swamps. Estuarine marshes are

uncommon in Puerto Rico because most of these habitats were destroyed by development and past agricultural activities or because mangrove forest species outcompete the salt marsh species in tropical coastlines.

Estuarine coastal flats—These salt flats or salinas are frequently positioned to the 

rear of coastal fringing mangrove swamps on the south coast of Puerto Rico in

areas that have access to sea water. The sea water then evaporates and produces

high salt concentrations in the water and soils. Species that can be present are

Avicennia germinans L. (black mangrove), Salicornia perennis Mill. and S. virginica L. (glassworts), Batis maritima L. (saltwort), and Sesuvium portulacastrum L.

(sea purselane). When flooded, these form hypersaline lagoons.

Estuarine aquatic beds—These wetlands are found in coastal waters and are sometimes referred to as underwater “marine prairies.” Most aquatic seagrass beds are

likely to have Thalassia testudinum Konig (turtle grass) present, but there are six

other seagrasses in Puerto Rico’s waters, including Syringodium filiforme Kutzing

(manatee grass), Halodule wrightii Ascherson (shoal grass), and Halophila spp.

(dwarf seagrass). These systems are frequently located in lagoons to the rear of

coral reefs and in open shallow waters in front of red mangrove swamps. Large

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estuarine beds are also found in the waters of La Parquera, Boquerón Bay, and the

bay at Isla Verde. A more detailed review of seagrasses follows.

Estuarine and marine open water reef wetlands—Where reefs are exposed or 

near the surface, are classed as a wetland. When they are permanently inundated

and in deeper water, they are considered deep water systems. A detailed description

of coral reefs follows.

Why have we lost so many wetlands in Puerto Rico, the United States, and the 

world? In most instances the cause was simple habitat alteration. The largest percentage of habitat loss has been associated with agricultural activities. The following list describes the ways wetland ecosystems have been destroyed or degraded in

the Puerto Rican landscape. These include both natural and human causes:

Natural causes:

➢ Sea-level rise

➢ Hurricanes and other storms

➢ Erosion

Human causes:

➢ Drainage for agriculture and mosquito control

➢ Dredging and stream channelization for navigation and flood control

➢ Filling for road construction and development of residential, commercial,

and industrial sites

➢ Construction of dikes, levees, dams, and seawalls for flood control, 

water supplies, irrigation, and from storm protection

➢ Effluent and runoff from agriculture, domestic sewerage, industrial and

commercial sites

➢ Mining of gravel, limestone, sand, and other materials

➢ Hydrological alterations resulting from road construction, drainage 

canals, dams, housing, industrial and port construction

➢ Cutting of mangroves for fuel sources for households and sugarcane 

mills

Wetlands Regulation

All of the above-mentioned activities were largely unregulated until the past couple

of decades. Today, wetlands are protected and require permits if they are to be

altered. There is no uniform national or commonwealth wetland legislation.

Instead, wetlands are regulated by a series of federal and commonwealth statutes

with regulations overseen by four U.S. agencies: the Environmental Protection

Agency (EPA), U.S. Fish and Wildlife Service, National Resources Conservation

170
Service and the U.S. Corps of Engineers (COE). The Puerto Rico Department of

Natural and Environmental Resources and the Planning Board of Puerto Rico are

the primary commonwealth agencies overseeing wetland protection. Each agency

has areas of vested interest and serves as the lead agency overseeing related wetland activities and oversight in these interest areas. Any operations related to

dredge and fill projects are generally controlled by the COE who has the regulatory

responsibility of issuing or denying construction permits in navigable waters of the

United States based on the 1899 Rivers and Harbors Act, Section 404 of the 1972

Clean Water Act, and other legislation (Adams and Hefner 1994). The 404 legislation is the most often used federal legislation protecting wetlands because it regulates discharge of dredged or fill materials into wetlands. Large projects require 

full permit applications, whereas small projects less than an acre with minimal 

wetland impact are typically covered on the basis of simple permits issued under

the Nationwide Permit System. These permits can be granted at the local field

office of the U.S. COE. The EPA has final review and veto power for all permit

applications. Full permit applications can be both time consuming and expensive as

they have to be reviewed by all concerned oversight agencies and the public. This

can lead to lawsuits that attempt to block the project and deny permit application.

Frequently, larger and more complex permit applications will require mitigations

as a part of the permitting process. In those instances, the permittee must minimize

wetland impacts and, in some cases, rehabilitate nearby degraded wetlands or construct new wetlands at a different site to meet “no net loss” mandates for our

national wetlands management program. Unfortunately, many wetlands have been

filled without authorization, but less than half of the illegal fills have been restored.

Many field offices of the U.S. COE have inadequate staff to handle the permit

applications and the heavy case load investigating illegal activities. This also 

makes it difficult to enforce compliance with permit conditions when mitigation is

required. The same is true with other responsible federal agencies in Puerto Rico.

As indicated previously, Puerto Rico’s wetlands are valuable for the benefits

derived by humans and for what they supply in terms of ecological services. They

are especially valuable as wildlife habitat. The salt flats and marshes of southwest

Puerto Rico are key to providing large numbers of migratory shore birds with resting and feeding areas as they migrate from North America and the Caribbean and

South America and back. Freshwater marshes throughout Puerto Rico provide 

habitat for nearly 100 species of migratory and resident birds. The mountain wetland forests in the Luquillo Mountains are the last habitats with wild populations 

of the endangered Puerto Rican parrot. Areas associated with the island’s wetlands

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provide feeding and nesting habitat for endangered sea turtles and manatees. The

majority of commercially important food fish and shellfish come directly from

coastal wetlands or wetlands serve as the nursery habitat for these species.

One of the most important freshwater wetlands now protected is the Tortuguero

Lagoon National Reserve. It is a spring- and seep-fed wetland with an open-water

lake on the north coast, Puerto Rico’s only natural lake (fig. 53). There are nearly

700 plants present, and it has a variety of palustrine wetlands, including a tropical

bog with insectivorous plants. The description of this flora by Roy Woodbury2

includes 217 marsh species, 78 grasses, 79 sedges, 17 orchids, and 38 ferns. There

were 69 rare and endangered species, 17 endemic to Puerto Rico, 7 endemic to

Tortuguero, and 26 species new to the flora of Puerto Rico (Lugo and Brown

1988). This is exceptional biodiversity for an area of 225 hectares (556 acres).

Wetlands are often referred to as the “landscape’s kidneys” because they perform valuable functions related to eliminating or storing potentially harmful material. They are also called “nature’s supermarkets” because of the extensive and

complex food webs present and the vast array of species associated with them.

Thankfully, wetlands appear to be on the rebound in Puerto Rico. It is hoped that

greater protection will be provided to existing remnants and newly developing 

wetlands. Wherever possible, reclamation and mitigation procedures should be

applied to permitted development sites, especially throughout the coastal areas.

This is especially so for the north coast where most palustrine freshwater wetlands

are located owing to the higher concentration and length of rivers there. The north

coast is undergoing rapid and intense urbanization, and, because of all of the vital

services supplied by the wetlands, it is essential that wetlands not be destroyed or

degraded in this area of rapid growth. They are essential to maintaining water 

quality in the rivers, bays, estuaries, and open sea associated with the entire Puerto

Rican coastal zone. Puerto Rico can ill afford to lose its wetlands. Wetlands in

Puerto Rico are especially vulnerable because they are fairly small, interrupted in

distribution, and often located in areas that people want to develop or alter in some

way. Historically, wetlands have been looked upon as wastelands. Puerto Rico’s

wetlands need better oversight and protection because they represent habitats of

concern and are not wastelands. Once gone, they will likely be gone forever, and

with their disappearance will follow the loss of all those free ecological services

and the many species they support.

172

2 Woodbury, Roy, unpublished material available through A.E. Lugo.
Many people, including professional scientists and elected officials, think that

our problem of wetlands loss is no longer much of an issue because it is now possible to rehabilitate degraded wetlands or make totally new artificial wetlands. A

report issued by the National Research Council (NRC 2001) indicated that current

approaches designed to guarantee “no net loss” of U.S. wetlands are basically a

failure. Artificial wetlands are a poor substitute for the real thing. Although 17 000

hectares (41,990 acres) of wetlands were created (on paper) between 1993 and

2000, many projects were never done, or only partially completed. Others had no

postconstruction monitoring to verify they were working as designed. Why? The

NRC says that the projects were not being adequately tracked. They also indicated

that the difficulty in designing projects that require intermittent waterflows results

in different mixes of plants and animals when the water regime is not correct. The

NRC further indicated that wetlands difficult to reproduce, such as bogs, should be

left alone. They also recommended:

➢ Permits be closely tracked

➢ Continuing research on design and reclamation be maintained in order 

to find out what types of wetland projects work

➢ Stricter enforcement standards be devised for all projects

➢ Improved long-term monitoring be implemented

➢ Permitting be at the watershed level, not on a simple project-by-project

basis

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Guide To The Ecological Systems Of Puerto Rico

Figure 53—View of Lake Tortuguero wetlands. 

L. Miranda Castro
General Technical Report IITF-35

Should these recommendations, especially the watershed approach, be implemented, it will require much better cooperation, coordination, and management by

all agencies involved in the wetlands management program.

For further reading see Álvarez-López 1990, Cowardin et al. 1979, Dahl 2000,

del Llano 1988, Frayer et al. 1983, Little and Wadsworth 1964, Lugo and Brown,

1988, Mitch and Gosselink 1993, Newton 1981, Reed 1988, Tiner 1984, U.S.

Corps of Engineers 1978, U.S. Department of the Interior 1990.

Coastal Ecosystems

Puerto Rico lies slightly south of the Tropic of Cancer and environments are tropical owing to proximity of constantly warm ocean water and air masses. The warm

waters make environmental conditions suitable for large numbers of tropical

marine organisms, many not found above the Greater Antilles.

The surrounding ocean water plays an important role in moderating the climate

of the island. Typical of a tropical climate, there are two seasons: a warm rainy 

season from May through September, with temperatures in the 30 oC range (mid to

high 80s oF) and a mild dry season, October through April, with temperatures averaging in the mid to high 20 oC (70s oF). Occasionally temperatures drop into the

low 20s oC (70s oF). Temperatures are rarely lower, except in the mountains.

During these periods, there is only a slight change in water temperature.

As is true of most inhabited tropical islands today, Puerto Rico has experienced

the pressures of agriculture, population growth, development, and construction in

the entire coastal plain area (fig. 54). As a result, many natural habitats typical of

the coastal fringe of the island and adjacent waters exist in a somewhat disturbed

condition, or are heavily modified to the point where they are no longer natural.

Coastal marine habitats constitute only 10 percent of the world’s ocean area, but

the coastal habitats contain an estimated 90 percent of all known marine species.

As with many ecological systems, beach systems are zoned. Figure 55 illustrates

the zones found in a typical beach front, and app. 3 recommends a location for

viewing coastal habitats.

Sandy Beach Habitats

Rachel Carson (1955) in The Edge of the Sea wrote:

The edge of the sea is a strange and beautiful place. All through the long 

history of Earth it has been an area of unrest where waves have broken 

heavily against the land, where the tides have pressed forward over the 

continents, receded, and then returned. For no two successive days is the 

shore line precisely the same. Not only do the tides advance and retreat in 

174
their eternal rhythms, but the level of the sea itself is never at rest. It rises 

or falls as the glaciers melt or grow, as the floor of the deep ocean basins 

shifts under its increasing load of sediments, or as the earth’s crust along 

the continental margins warps up or down in adjustment to strain and tension. Today a little more land may belong to the sea, tomorrow a little less.

Always the edge of the sea remains an elusive and indefinable boundary.

Coastlines throughout the world are being affected both from human assaults 

as our population expands, and as a result of sea level rise associated with global

climate change. Many areas are experiencing serious erosion problems as a result

of the rise, whereas others are seeing natural coastal ecosystems degrade or disappear as a result of development pressures. These problems are important issues that

need attention in Puerto Rico. Puerto Rico has major sand dune management problems because they are viewed as cheap, easy-to-access sources of sand for use in

construction.

Sandy beaches and dunes make up only a small percentage of Puerto Rico’s

518-kilometer (311-mile) coastline. Many tropical beaches are composed of carbonate sands produced from the disintegration of various shelled animals, hard

corals, and coralline algae. There is very little sand on Caribbean islands because

they have small insular shelves causing much of the sand to be lost to deeper areas

of the sea. Puerto Rico has few long, straight beaches. Luquillo is the largest, and

the reason it has sand is because it is locked in a bay. The same is true of Boquerón

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Figure 54—Intensive coastal zone development. 

J. Colón
General Technical Report IITF-35

176

Figure 55—

The anatomy of a typical beachfront.
Bay and its large sandy beach. Puerto Rico’s north coast has more sandy beaches

than does the south coast owing to its geographic configuration. Many of the shallow coastal sand deposits provide the necessary substrate for development of 

highly productive seagrass ecosystems.

Coastal sand systems appear to be all but lifeless, but, in fact, they are vital,

constantly changing, and quite interesting, ecologically. They are much more than

just a barrier to the sea. On open wet sandy shorelines, most of the inhabitants live

under the sandy surface in tubes and burrows or in spaces between sand grains.

They surface when waves pass over their habitats. This guide is not going to

review the variety of plants and animals likely to be encountered in wet and dry

portions of the sandy littoral (intertidal) zone, other than to indicate that there are 

a variety of worms, crabs, sand dollars, clams, amphipods, burrowing anemones,

protozoans, fungi, bacteria, and plankton (phytoplankton and zooplankton),

among others present. The main focus of this section will be to describe the higher

plant species and communities likely to be encountered in the supralittoral zone,

that is, from the high tide line into the adjacent sand dunes, and the outer true 

terrestrial zone, which may be forest covered.

The physical nature of a beach determines the type of vegetation present.

Beaches and dunes are rarely permanent natural structures, they are constantly

shifting and migrating based on wind, currents, tides, storms, and anthropogenic

activities. Beaches build up when the weather is calm and retreat when exposed to

large storm events. They are very dynamic habitats. Four factors affect beach stability: shape and orientation of the beach, sediment sources, wave energy, and sea

level rise. At any given time, a beach is in dynamic equilibrium. Beaches and dunes

are built by wind, waves, and currents, and then stabilized by specially adapted

vegetation. If vegetation is present, it responds as the sand system is altered. Beach

plants are adapted to colonize the shifting sands as long as the rate of sand migration is not too rapid. Many have spreading roots like Coccoloba uvifera L. (sea

grape). They also have large leaves, which can reduce windspeeds and cause sand

to drop at the base of the tree. Many grasses and herbs develop widespread rhizomes that promote extensive clonal populations and thus are referred to as dune

builders.

Key features to look for in sandy beach organisms are adaptations that protect

stems and leaves and help to reduce drying effects of wind, exposure to salt, and

physical abrasion by sand. They include:

➢ Asexual methods of reproduction via rhizomes, runners, and stem 

tipping

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➢ Protection from high heat (thick leaves, heavy cuticle, dense 

pubescence, rolled leaves, leaf position)

➢ Xerophytic water conservation adaptations (succulent stems, pubescence,

heavy cuticle, leathery leaves, waxy leaves, and small leaves)

➢ Sand collection mechanisms (large leaves, fibrous roots, and multiple

stems)

➢ Salt tolerance (sculptured growth form)

In general, beaches and dunes are zoned based on the degree that these environmental stress factors affect the plants present. The three general zones are open

beach, fore dune, and rear dune. Each of these has a group of plants that produce a

community typical of these zones (fig. 56).

The open beach supralittoral zone is a zone of extremes: cool/hot, salt/fresh,

wet/dry. As a result, it exhibits low productivity because few organisms are adapted

to the range of these variable conditions. This is the “dry” zone that most people

will likely put their beach towel on when they go to the beach for recreation. Most

of the organic matter present is deposited there by high tides or wind action. This

zone is physically unstable, thus difficult for most terrestrial plants to inhabit.

Fruits and seeds will be cast into the zone, and seedlings may become established

or they may be removed owing to shifting wind and waves (fig. 57).

If the beach accumulates sand deposits, one or more dunes will likely develop.

The first dune is called the fore dune. Fore dunes are also areas of extremes:

178

Figure 56—General view of a rocky beach front in the Piñones Vacia Talega area. 

G. Miller
cool/hot, salt/fresh, wet/dry conditions, but they are at least semistable; thus plants

can succeed in establishing permanent populations. Species diversity will be low

and most organisms will occupy specific zones based on environmental factors at

work on that habitat. Dunes typically have a couple of beach grasses and associated

forbs present adapted to salt spray exposure and sand blasting, and exhibiting rhizomatous growth. They are salt tolerant and unharmed by occasional submergence

or sea water overwash. Their seeds generally float. The species present can tolerate

strong winds either by producing flexuous stems or growing prostate on the sand’s

surface. Plants typical of this zone in Puerto Rico are:

➢ Sporobolus virginicus (L.) Kunth. (beach dropseed or salt grass)

➢ Paspalum vaginatum Swartz. (sea paspalum)

➢ Spartina patens (Ait.) Muhl. (sea grass)

➢ Cakile lanceolata (Willd.) O.E. Schulz (sea rocket)

➢ Canavalia maritima (Aubl.) Thouars (sea bean)

➢ Ipomoea pes-caprae (L.) R. Br. (beach morning glory)

➢ I. stolonifera (Cyrillo) Poiret (fiddle-leaf morning glory)

➢ Sesuvium portulacastrum L. (sea purselane)

➢ Cenchrus echinatus L. (sandspur)

All of these species are sand stabilizers and generally extend into the supralittoral open beach from the fore dune via rhizomes or runners. If the fore dune is

fairly stable, it may develop an evergreen hedge dominated by xerophytic woody

scrub species. The “hedge” is rarely over 0.5 meter (1.5 feet) high. Typical species

are:

➢ Borrichia arborescens (L.) DC. (sea ox-eye aster)

➢ Chrysobalanus icaco L. (coco plum)

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Figure 57—Generalized view of a sandy beach.
General Technical Report IITF-35

➢ Smilax coriacea Spreng. (cat briar)

➢ Coccoloba uvifera L. (sea grape)

At the top of dunes, other woody species may include:

➢ Plumeria alba L. (frangipani)

➢ Anthacanthus spinosus L. (beach spine)

To the rear of the dune, especially if high and stable for an extended period,

dry seasonal evergreen woodland may be present, including:

➢ Scleria microcarpa Nees (beach rush)

➢ Calophyllum brasiliense Camb. (Santa-María)

➢ Annona glabra L. (pond apple)

➢ Coccoloba uvifera L. (sea grapes)

In depression areas where salt content is high owing to evaporation, halophytic

(salt-tolerant) species will dominate, such as:

➢ Salicornia bigelovii Torrey. (glasswort)

➢ Batis maritima L. (saltwort)

Trees and shrubs may be present naturally in these zones, or planted to reduce 

beach erosion. Woody species typical of beaches throughout Puerto Rico are:

➢ Cocos nucifera L. (coconut palm)

➢ Suriana maritima L. (baycedar)

➢ Casuarina equisetifolia L. (Australian pine)

➢ Coccoloba uvifera L. (sea grapes)

➢ Conocarpus erectus L. (buttonwood mangrove)

➢ Bursera simaruba (L.) Sarg. (Gumbo limbo)

➢ Chrysobalanus icaco L. (coco plum)

➢ Dalbergia ecastaphyllum (L.) Taubert (chicken wood)

A profile of three trees typical of the beach community follows, including

Cocos nucifera L. (box 20), Coccoloba uvifera L. (box 21), and Casuarina equisetifolia L. (box 22).

All of these species can colonize and maintain themselves on sandy shorelines.

As indicated, they are salt tolerant and may exhibit salt and/or wind shearing or

training. In other words, due to salt effects (chlorosis) on plant tissue, or sand/wind

blasting causing death of windward buds and tissues, the plant exhibits a growth

form that appears sheared or wind trained. The parts of the plant on the windward

side grow little, whereas those on the leeward (protected) side grow more. This

growth form is typical of beaches and mountains. Generally, salt spray is the most

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Continue on page 186
Box 20. Cocos nucifera L. (coconut palm)

When you hear the words “tropical 

island,” 8 out of 10 times what comes to

mind are white sandy beaches studded

with palm trees. The coconut palm 

(Cocos nucifera) belongs to the 

Palmaceae family and is distributed

throughout the coastal areas of the 

tropics and semitropics. Coconut palms 

are not native to Puerto Rico. They are

thought to have been introduced to the

Caribbean islands in the early colonial

period. Their origin is thought to be 

Indo-Malayan. Coconuts are not only 

tall beautiful trees, but they are also very

economically important. They are an allpurpose tree in that all parts have value.

Often called “trees of life” on tropical

islands, they rank as one of the world’s 

top 10 most useful trees. Simpson and Ogorzaly (1995) quoted a southseas

proverb, “He who plants a coconut tree, plants food and drink, vessels and

clothing, a habitation for himself, and a heritage for his children.” Their trunks

can be sawed into termite-resistant boards for construction. Whole trunks are

used for marine posts and can be lashed together to make rafts. Their giant

leaves make excellent thatch and fencing, and their fruits provide both solid

and liquid foods and oil. One of the most popular drinks in the tropics is cold

coconut milk and sold as “cocos fríos” (liquid endosperm) along roads. Once

solidified, the endosperm becomes the white coconut meat used for confections. The shell of the nut (coir) is often made into rope, floor mats, industrial

filler, and road and riparian zone riverbank stabilizers. The hard seed coat is

crushed and used for charcoal filters. Their immature flowers can be baked

and eaten by humans or used for animal food. Many people plant them as

ornamentals around their homes. This tree supplies jobs to many people in the

tropics, especially in countries like the Philippines, Indonesia, and Mexico. 

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Guide To The Ecological Systems Of Puerto Rico

View of fronds, trunk, flowers, and fruit of

Cocos nucifera L. (coconut palm)
General Technical Report IITF-35

182

Box 20. continued

Coconuts can be

seen throughout most 

of Puerto Rico’s sandy

beach zone, throughout much of the coastal

plain, near roads,

homes, and parks.

Large commercial 

plantations have 

all but disappeared in

Puerto Rico. Coconuts

are regularly harvested

by local drink stand

operators and confection makers. Before 

leaving Puerto Rico, try a local ice cream favorite—helado de coco—sold on

street corners from push carts.

Coconuts require a warm, wet climate with little diurnal or yearly temperature swings. In dryer areas, general size and fruit production decline. They

grow best in deep, well-drained, sandy loam soils and can tolerate some exposure to saltwater, such as storm surges along coastal beaches. Coconuts will be

seen well into the mountains of Puerto Rico and are common up through 800-

meter (2,624-foot) elevations, especially along roads with nearby houses where

they are planted for their fruit production and beauty.

Coconuts are majestic trees with some of the largest leaves (fronds) known

to the plant world (up to 6 meters or 20 feet long). They have a unique growth

form with 24 to 36 fronds growing out of the tall branchless trunk. The fronds

are compound with many pairs of leaflets. About a dozen new fronds are produced yearly. When a frond dies and falls, it produces a scar on the tree’s

trunk. To age palms, count leaf scars and divide by 12. Trees in the tropics

cannot be aged by counting annual growth rings in the secondary xylem

(wood). Palms are unusual in that they are monocots. Most monocots are herbs

with a different growth strategy than trees from dicot families. A coconut tree

trunk is actually composed of overlapping sheathing bases of the fronds. If the

An “helado de coco” vendor in the Plaza at Guayama.

G. Miller
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Guide To The Ecological Systems Of Puerto Rico

Box 20. continued

growing tip is damaged or eaten, the tree will die. Coconut trees may live for

decades.

Coconuts begin flowering around 6 years of age, and at maturity may 

produce 40 to 100 nuts per year. The fruits grow for about 6 months and then

take another 6 months to ripen, at which time they change from green to yellow, and when they fall they may be brown. If the nuts fall into the sea, they

will float for months and sea currents are one of their primary vectoring

agents. They may travel thousands of miles before being lodged on a foreign

beach. They are easily germinated and may geminate while still on the tree.

The young are frequently observed developing on the beaches of the island.

Growth is related to nutrient and water relations in the soil. Under good conditions they may grow to a height of 30 meters (100 feet). They grow best in

open habitats but can be used as a canopy species in a multicrop agroecosystem. Puerto Rico’s largest coconut palm is located in Carolina. Its height is 

28 meters (92 feet), it has a crown spread of 5.3 meters (17.4 feet), and its 

circumference is 121 centimeters (48.5 inches).

Root development is from the large swollen trunk base. Because they typically grow in wet places, deep taproots do not form; instead they are supported

by a vast network of adventitious fibrous roots. They radiate for several meters

from the base and do an excellent job in supporting the tree, even in hurricane

winds. 

A number of insects attack coconuts, such as scarab beetles, scale insects,

and moths. The worst infection is a condition called lethal yellowing, which is

caused by a mycoplasma-like organism. Many plantations have been destroyed

in the Caribbean in the last few decades. The crown of the tree drops off and

the dead trunk remains, producing an appearance of a tree killing zone. Once

infected, the tree dies within 5 months. Many resorts that featured beautiful

palm-lined beaches have had major infections including Miami Beach, Key

West, Palm Beach in the United States, and on beaches in Cuba, Jamaica, the

Cayman Islands, and Mexico. Fortunately, there are resistant varieties being

used to replant the devastated populations. Puerto Rico has had lethal yellowing infections, and the dead trunks can still be observed standing at Caña

Gorda on the south coast in the Guánica Forest. Puerto Rico has 13 native or

naturalized species of palms, two of which are endemic.

For more information on this species, see McCoy 1988, Moore 1948,

Parrotta 1993, and Royal Botanic Gardens at Kew 1998.
General Technical Report IITF-35

184

Box 21. Coccoloba uvifera L. (sea grape)

As you walk along most beaches in 

Puerto Rico you are likely to encounter 

trees that appear to have large clusters

of green or purple grapes hanging from

their branches. This tree is sea grape. 

It is a Neotropical species that occurs

throughout coastal Bahamas, southern

Florida, the West Indies, Central

America, and both coasts of tropical

South America. It has been introduced

to various beach habitats in the Pacific

region. It most often grows on sandy

shorelines and dunes, but it can also 

be found on rocky shorelines such as

the limestone outcrops in the Guánica

Forest. Heavy winds may cause the tree to grow prostrate to the ground 

surface or as a bush. Often, it will have partially brown leaves, the result of

exposure to salt spray.

It is easily recognized by the edible grape clusters and large, thick, alternate, orbicular leaves. Its trunk is rarely straight because its habitat is windswept. It is an early colonizer of shorelines and has high tolerance to salt spray

exposure. It rarely grows away from the coast, although today it is being

grown as a horticultural species around homes, businesses, public parks, and

highway medians. It grows best in full sunlight. 

Sea grapes have separately sexed trees (dioecious) and begin to flower at

about age six. The fragrant flowers and fruits develop as terminal racemes, and

their flowers are green-white. Fertile flowers mature into a fleshy edible fruit.

They flower and fruit throughout the year. The fruits and seeds are dispersed

by frugivorous birds and bats. Germination and new seedling growth can occur

throughout the year.

Growth is strongly influenced by exposure to wind and salt spray, and

many individuals may be misshapen and show wind shearing. Sea grapes

rarely exceed 18 meters (60 feet), most are less than 7.6 meters (25 feet). The

largest sea grape in Puerto Rico is in Guánica. It is 9 meters (29.5 feet) tall,

The leaves, flowers, and fruit of Coccoloba

uvifera L. (seagrapes).
Box 22. Casuarina equisetifolia L. (Australian pine)

Another introduced coastal tree very

likely to be encountered on the 

beaches of Puerto Rico is Casuarina

equisetifolia L., commonly called 

Australian pine. Its common name 

relates to the fact that this tree grows 

in Australia, but it is not a pine. It is 

not even a gymnosperm. Casuarina 

is a fast-growing dicotyledonous 

evergreen tree requiring full sunlight 

that achieves heights of 45 meters

(148 feet). Trees in Puerto Rico 

rarely exceed 30 meters (100 feet), 

although the tallest tree reported in 

Puerto Rico is a 43-meter (141-foot)

Australian pine. Now distributed throughout much of the tropical world’s

sandy coasts, it is extensively used for reforestation on degraded lands and as

a plantation monoculture from China to Africa and the Caribbean. It is widely

planted throughout Puerto Rico’s lower elevations, especially along the coast.

They are often used to create windbreaks. 

Australian pine does not develop a wide full crown; rather it is slender and

open, with drooping branches. One of its most distinguishing characteristics is

185

Guide To The Ecological Systems Of Puerto Rico

The stems and fruit of Casaurina equisetifolia

L. (Australian pine)

Box 21. continued

has a crown spread of 8.5 meters (28 feet), and has a circumference of 124

centimeters (49.5 inches).

The fruits of sea grapes are edible as a raw fruit, and are used for jellies,

wine, honey, and native medicines. Tannins can be extracted from the bark,

and the wood can be used for firewood, charcoal, and posts. Its primary value

is ecological for beach stabilization along sandy coastlines. Coccoloba uvifera

is native to Puerto Rico, and there are 13 other species in the genus; four are

endemic to Puerto Rico.

For more information about this species, see Craig 1984, Little and

Wadsworth 1964, and Parrotta 1994.
General Technical Report IITF-35

Box 22. continued

that the stem looks remarkably similar to that of the ancient genus Equisetum

(horsetails). The stems are segmented and form a twig that appears to be 

needle-shaped, much like a true pine needle. Actual leaves are very small,

scale-like, whorled at nodes, and less than 2 millimeters (1/32 inch) long. The

main photosynthetic surface is actually the tree’s twigs, which remain evergreen and are 22 to 45 centimeters (9 to 18 inches) long. Flowering and fruiting

goes on throughout the year. Separate male and female flowers protrude from

the scales on the same plant (monoecious). The pointy fruit is a multiple that

produces a cone-like structure of achenes; which releases one-winged seeds at

maturity. The tree and fruits are sometimes used for Christmas decoration.

The tree’s main value is for beach stabilization, windbreaks, poles, posts,

charcoal, and fuel wood. It produces a hard wood that cracks and splits easily.

Its bark produces tannins, dyes, and home medicines. Because of its pine-like

features, it is often planted as a horticultural species around homes and in

parks. Australian pines in Puerto Rico have recently been attacked by a blight.

Like leguminous species, Casuarina has nodules with nitrogen-fixers, which

allows it to grow in degraded soils; thus it can be used in soil reclamation

projects. Young trees are very resistant to wind damage and can survive hurricane force winds.

For more information on this species, see Little and Wadsworth 1964,

Midgley et al. 1983, National Research Council 1984, and Parrotta 1993.

186

critical environmental factor limiting adaptability of plants in coastal communities

both as related to salt buildup in the soil and tissue chlorosis in the aerial organs.

In Puerto Rico, the only significant sand dunes are on the northern coast

because it is a high-energy coastline. Coastal dunes range from small sand mounds

to dunes 15 meters (50 feet) tall, such as those at Isabela. Unvegetated dunes can be

destroyed by wind or waves, the same forces that produced them. Coastal dunes

build when sand is blown or washed into areas with vegetation. As long as the rate

of sand deposition does not exceed that of the plant’s ability to grow, the dune will

be stabilized. Dunes are critically important because they act like bulwarks against

surging sea waves and as a source of sand to replenish natural beach erosion.

Unfortunately, many dunes have disappeared in Puerto Rico owing to illegal poaching of sand for commercial activities, as well as permitted overextraction activities
187

Guide To The Ecological Systems Of Puerto Rico

(fig. 58). For a review of coastal zone and dune management issues, see Bush et al.

(1995), Living With the Puerto Rico Shore. This is one in a series of books done in

cooperation with Orrin Pilkey of Duke University, considered by many the United

States’ authority on human impact on the coast.

Dunes and beaches are important during hurricanes because they serve to

dampen large waves and tidal surges when they interact with sand and wash it into

the sea. To gain the benefits of dunes, they must be protected. Activities that

degrade sand beaches and dunes include:

➢ Sand removal for construction and fill

➢ Flattening of dunes for building construction: homes, condominiums, 

and hotels

➢ Constant foot traffic in vulnerable areas that kills vegetation or breaks 

the dune line

➢ Hard stabilization projects such as jetties, sea walls, and groins

➢ Development of harbors, marinas, and docking facilities

➢ Dredging of channels that can affect long shore littoral drift of sand

➢ Oil spills

All these activities result in removal of the plants/communities and, in many 

cases, the sand itself, causing the loss of filtering, stabilization, protection, and productivity provided by the beach ecosystem. Puerto Rico’s coastline is experiencing

shoreline retreat (beach erosion). In some places it is negligible, such as on rocky

Figure 58—The giant sand dunes of Isabela showing the effects of illegal removal of sand.

G. Miller
General Technical Report IITF-35

shorelines. On the other hand, on some of the best tourist sandy beaches, such as

those at Boquerón or the Condado, retreat can be measured in meters after major

storms.

Rocky Shoreline Habitat3

Rocky shorelines are found in many areas of Puerto Rico. Although the mean tidal 

fluctuation is only 0.5 meter (1.5 feet), exposed rocky shoreline areas of the

Pleistocene reef formation can produce an intertidal platform up to 50 meters (165

feet) wide. This area of the coast exhibits unique zonation patterns and morphological, physiological, and behavioral adaptations by organisms present in this stressed

environment. The upper zones and organisms are subjected to the greatest stress.

Rocky shores are in direct contrast to sandy shores by the almost total lack of sand.

As is the case with sandy shores, pristine unspoiled rocky shores are rare today. A

rocky shore may exhibit rock that clearly shows its origin as coral with the elongated grooves representing each coral cup through time. The horizontal lines are

basal plates, or the bases of the cups, as the polyps extended the cups by building

new floors, constantly enlarging the size of the colony. Other rocky shores are

beach rock formations resulting from cementing of sand, shell fragments, and precipitation of calcium carbonate coming into the sea from drainage out of the karst

region.

There may be a number of Chitons and snails on the coral chunks. At the upper

margins of this beach, in the detritus, many small hermit crabs in snail shells will

likely be found. These are juvenile Coenobita clypeatus (purple-clawed land crabs).

They are still located near the sea, but when they reach maturity, about 2 centimeters (three quarters of an inch) and larger, they will move inland, to return to the

sea only to spawn. They are able to retain water inside their adopted shells to keep

their gills moist. This lung-like apparatus allows them to carry on terrestrial respiration. These are the crabs sold in the United States in pet shops. Typical rocky

zones and their species are described in this section. Their position is based on

daily tidal fluctuation, which in Puerto Rico is only 0.5 meter (1.6 feet). Rocky

shorelines provide one of the best natural stages for observers to see species zonation based on a series of physical and biological limiting factors at work on this

ecosystem that is transitional between land and sea. Many of the organisms will

exhibit special adaptations for maintaining themselves on this high-stress environment such as holdfasts, suckers, and glue.

188

3 See appendix 2 for dangers to be aware of on rocky beaches.
189

Guide To The Ecological Systems Of Puerto Rico

Rocky beach conditions that will be present are:

➢ Hard stable substrate ➢ Temperature-hot/cool

➢ Water-wet/dry ➢ Human activities

➢ Salinity-salty/fresh ➢ Oil spills

➢ Oxygen-air/water ➢ Industrial effluents-air and water

➢ Wave energy-calm vs. storms ➢ Collecting

➢ Predation-aquatic/terrestrial ➢ Construction

➢ Interspecific competition- ➢ Wind-vegetation response

Balanus and Chthamalus

On the open rocky shore, zonation is clearly depicted in the color of the rock. 

The white zone is revealed as a white patina on the very tips of the rocks. This

region is inundated only by spring storm tides, so it is dry much of the time. Along

the landward margin of the beach there may be gnarled, almost prostrate bushes of

Sesuvium portulacastrum L. (sea purselane), Batis maritima L. (saltwort) and

Conocarpus erectus L. (buttonwood mangrove), and other shrubs or trees. These

are typical inhabitants of the white zone. They have been shaped by the strong

wind and salty atmosphere of their environment. The rock may be covered by

lichens or blue-green algae, which exude slime coatings to prevent desiccation. A

snail that is an indicator organism of the white zone is the white or grayish white,

globose, Tectarius muricatus (beaded periwinkle). This snail feeds at the waterline

at night, but during the daytime it moves up into the white zone and beyond, sometimes 10 meters (33 feet) or more above the waterline (table 18).

Most of the beach is in the gray zone, indicated by pitted gray rocks, dissolved

by extensive exposure to saltwater and rain. Limestone, formerly the calcium 

carbonate skeletons of corals, the calcareous alga (Halimeda), and other calcareous

species, the shells and spines of sea urchins, and others, is quite soluble in water. It

dissolves at a variable rate, resulting in the highly dissected appearance of the gray

zone. Three snails are indicators of this zone: Littorina zigzag (zebra periwinkle),

Nodilittorina tuberculata (common prickly winkle), and the large Nerita peloronta

(bleeding tooth nerite). Nodilittorina is a small gray snail with pointed, randomly

distributed tubercles. Littornia zigzag is usually less than 1 centimeter (less then

or equal to one-half inch) long with a distinctive gray herringbone pattern on a

cream background. 

The Neritas are the best indicators of levels of the gray zone. Nerita peloronta

(bleeding tooth nerite) is found high up in the gray zone. A smaller nerite with pink

and black flecks and deep cords running the length of the shell is Nerita versicolor

(four-toothed nerite). It is found lower down in the gray zone, sometimes in the
General Technical Report IITF-35

190Table 18—Indicator organisms of each tidal zone on a rocky shore White zone Gray zone Black zone Yellow zone Pink zone

Beach Supralittoral Periodic inundation Intertidal Sublittoral

(Snails) Upper (snails) In tide pools (Snails) Upper (Snails)Tectarius muricatus Nerita peloronta Puperita pupa (Chitons) Cittarium pica

Nodilittorina tuberculata Planaxis nucleus Acanthopleura granulata

(Land plants) Littorina zigzag Batillaria minima (Inside B (Sea urchins)Sesuvium portulacastrum minima shells are the tiny (Limpets) Echinometra lucunter

Ipomoea pes-caprae Middle and lower hermit crabs, Clibanarius Fissurella barbadensis

Batis maritima Nerita versicolor tricolor) F. nodosa (Algae)

Nerita tessellata Diodora listeri Caulerpa species

(Others) On rocksInsects (Crabs) The snail, Nerita tesselata, (Barnacles) Corals

Spiders Grapsus grapsus becomes more common here Chthamalus stellatus Millepora spp.

Acropora palmata

(Algae) (Algae) Lower Siderastrea radians

Bostrychia Bostrychia common, giving (Chitons)

zone its typical black color Chiton tuberculatus

C. marmoratusC. squamosus(Barnacles)Tetraclita squamosa

stalactofera

(Snails)Purpura patulaThais haemastomaT. rusticaTurbinaria turbinata(Algae of upper and lowerYellow zones)Sargassum sp.Padina sanctae-crucisValonia ocellataDictyosphaeria sp.

Short, fuzzy algae such as:

Cladophoropsis sp.Heterosiphonia sp.Champia sp.
black zone. Nerita tessellata (checkered nerite) is smaller than the other nerites and

has a black and white checkered appearance. It moves up and down with the tide

and will be found in the yellow zone or intertidal sometimes, but most of the time

is an inhabitant of the lowest parts of the gray zone. The gray zone is submerged

for only a few days a month during spring tides.

The black zone is a narrow band (often not visible on the island) inundated

more often—more than half the days of every month. It is black because of the 

predominance of Bostrychia spp. (red alga).

The yellow zone is inundated daily. It corresponds to the term littoral or intertidal, more commonly used in northern waters where rocks do not exhibit such

clear-cut color variations according to their degree of inundation.

In the lower black and upper yellow zones, the first of three common species

of chitons can be found. Acanthopleura granulata (fuzzy chiton) is so called

because its girdle is fuzzy, lacking the typical snakeskin appearance of other common chitons. The other two species of chiton are found in the lower yellow zone

and rarely exposed. Chiton tuberculatus (West Indian chiton) has chevrons or diamonds of tubercles on its plates, one large chevron per plate. The C. marmoratus

(marbled chiton) has a brown and tan marbelized pattern on its shiny plates. These

water-covered zones may exhibit algae such as Sargassum spp. (sargassum),

Valonia ventricosa J. Agardh (sea pearls), Dictyosphaeria cavernosa (Forsskal)

Boergesen (green bubble alga), and Caulerpa spp. (feather algae).

At low tide, note the pink zone, another narrow band, this time covered with

Goniolithon strictum (Foslie) Setchell & Mason (pink calcareous alga), and other

coralline algal species can be observed. This zone is located at the base of the 

yellow zone. It is submerged except for a few days a month when low spring tides

expose it. It may have hard corals such as Acropora palmata (elkhorn) and

Siderastrea radians (shallow starlet) present.

Tide pools—

Tide pools are sometimes referred to as microecosystems of the sea. Tide pool

water levels vary from ankle to knee-deep, and the pool may contain a number of

Diadema antillarum (long-spined black sea urchins), thus one should be careful 

not to step on them. The pools may have wide swings in factors such as temperature, carbon dioxide/oxygen levels, pH, salinity, and water volume. Stoichactis

helianthus (sun anemones), resembling greenish rugs, may be dominant organisms

in the pool. There is usually a mat of Padina sanctae-crucis Boergesen (tan petticoat algae). It has thin calcareous bands running across a flat, encrusting, tan 

thallus.

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Guide To The Ecological Systems Of Puerto Rico
General Technical Report IITF-35

Tide pools may contain a number of species of fishes. Most are damselfishes 

of one sort or another. Most common are beaugregories and sergeant majors

(Abudefduf saxatilis). There are many types of gobies and blennies, usually well

camouflaged and visible only when they characteristically dart from one rock to

another. Sometimes you will see one sticking to the vertical wall of a tide pool 

by its ventral sucking disk. Some pools, usually those with little access to the sea

and no tidal current, are covered by colonies of the famous Acetabularia crenulata

Lamouroux (mermaid’s wineglass), which looks like dusty green miniature umbrellas about 2 centimeters (1 inch) high.

Some tidepools and adjacent flats have crevices often containing the

Echinometra lucunter (red rock urchin). These have medium-sized spines, usually

blackish, contrasting with a bright red to reddish-black test. Do not make the 

mistake of trying to pick up a Diadema, thinking that it is just a particularly dark

specimen of Echinometra. Diadema’s spines are like hypodermic needles with

backward pointing barbs at their ends.

Coastal scrub—

Some rocky shores have elevated cliff exposures that may have a dry coastal scrub

community present. Some of these exhibit extreme wind/salt shear and may only be

a few centimeters (inches) tall. There are three species likely to occupy the leading

edge of this community: Strumpfia maritima Jacq. (bonzai plant), Coccoloba

uvifera L. (sea grapes), and Conocarpus erectus L. (buttonwood mangrove). The

stunting and salt/wind shear will be exaggerated to the point that the species will

create a “carpet effect” over the rocky surface. Vertical growth is almost impossible

owing to the stressors at work on the lead vertical meristems of the branches; thus

virtually all growth is horizontal. In some cases, the vertical extension of the tree

will be measured in centimeters (inches), whereas the horizontal growth will be in

meters (feet). The low prostrate growth form exhibited by these trees is due to loss

of their lead apical meristems causing a branched response similar to that achieved

when a woody plant is pruned. Farther away from the cliff’s edge and as the plants

provide protection to each other, greater vertical extension is observed. Eventually,

more normal vertical growth is achieved. Excellent coastal scrub can be observed

in the Guánica forest along the coastal road.

Other plants typical of this community are:

➢ Batis maritima L. (saltwort)

➢ Borrichia arborescens (L.) DC. (sea ox-eye aster)

➢ Melocactus intortus (Miller) Urban (turk’s cap cactus)

192
➢ Opuntia rubescens Salm-Dyck (tree cactus)

➢ Opuntia dillenii (Ker-Gawl.) Haw. (prickly pear cactus)

➢ Plumeria alba L. (frangipani)

➢ Bursera simaruba (L.) Sarg. (Gumbo limbo)

➢ Comocladia dodonaea (L.) Urban (poison plant)

➢ Furcraea tuberosa (Mill.) Ait. (Puerto Rican century plant)

➢ Suriana maritima L. (baycedar)

The exact species present will differ from habitat to habitat.

At the outer limits of this community, the plants will appear to be growing on

exposed rock, which they are. However, their stem and root systems penetrate a

dissolation depression in the limestone substrate where there are small accumulations of soil and moisture. Growth is extremely slow in this habitat, and it is likely

these sea cliffs are just as they appeared at the time of European discovery. They

are probably one of Puerto Rico’s only examples of an old-growth community.

For further reading see Kaplan 1982, 1988 and Stephenson and Stephenson

1972.

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Chapter 5: Estuarine Ecosystems

Mangrove Forests

Some of the most intriguing forests found in the tropics are mangrove forests. 

They are unlike any other forest type in the world, as mangroves grow in sea water.

These forests are often referred to as tidal fringing forests because they live in or

create an ecotonal fringe along protected tropical coasts, lagoons, bays, and offshore islands. They also create a riverine fringe in deltas and farther inland along

riverine flood plains. They cover nearly 10 million hectares (25 million acres)

worldwide.

The term mangrove does not directly refer to a specific family, genus, or

species as when you say beech, spruce, or red oak. In the latter instances, members

of a particular family, genus or, in some cases, species actually define the forest

type. Mangrove is a general term that can refer to numerous families, genera, and

species of totally different taxons. What they have in common is tolerance to salt,

that is, they are halophytes. The term mangrove can refer to up to 19 plant families,

26 genera, and close to 80 species worldwide. Old World tropics have many more

of each taxon in comparison to the Neotropics. There are four common mangroves

typical to Puerto Rico and the Caribbean: Rhizophora mangle L.1 (red, box 23),

Avicennia germinans L. (black, box 24), Laguncularia racemosa (L.) Gaertn.

(white) and Conocarpus erectus L. (buttonwood). Table 19 compares the taxonomic, morphological, reproductive, and habitat attributes of these species. All

species are intolerant of frost.

The buttonwood mangrove is probably the least common of the four. The red,

white, and black mangroves owe their worldwide dispersal to their “sea-going”

seeds. Red mangroves are unique because their seeds germinate while still on the

parent tree. The flowers of red mangroves bloom for a few weeks on the tree while

pollination and fertilization take place. The fruits then form consisting of a single

seed. A shoot and root then sprout from the seed and grow until so heavy it drops

off the parent tree. This condition is called vivipary. When it falls, it can either

take root immediately or will float away with the tide. This seedling may float

around for almost a year until it lands in a location suitable for anchoring. In time,

the root tip becomes water-logged, turning the plant vertical. The suitable site is

sometimes a sandbar, but it will as likely be a shallow coral reef. The seedling then

anchors itself by sending out prop roots and grows rapidly, sometimes as much 

Guide To The Ecological Systems Of Puerto Rico

195

1 See appendix 1 for Common and Latin names. Continued on page 200.
General Technical Report IITF-35

196

Box 23. Rhizophora mangle L. (red mangrove) 

Most tropical forests have high 

species diversity. A distinct exception to this are coastal fringing 

forests composed of red mangroves 

and sierra palm forests in the high

mountains of Puerto Rico. These are

examples of natural monocultures.

Monocultures are generally associated with intensive agriculture or 

silviculture such as tobacco or 

various species of pine trees.

Rhizophora mangle L. (red 

mangrove) is found throughout the

tropical world from the Pacific 

islands to West Africa, the south 

coast of Florida, the Caribbean, and Central and South America. This distribution roughly approximates 30° N and S of the equator. It is a frost-sensitive

species. It grows in diverse climatic areas, from very dry to wet forest life

zones, with best growth occurring in wet areas. It prefers salty soils, with salty

or brackish water present. It develops best in areas protected from high wave

energy such as lagoons, or coastal river flood plains with tidal fluctuations,

often referred to as “fringing wetlands.”

Red mangrove is a very interesting tree, botanically and ecologically,

because it exhibits a series of rare traits, such as:

➢ Tolerance to high salt concentrations

➢ Natural monoculture

➢ Vivipary

➢ Stilt (prop) roots

➢ Detritally enriched nursery habitat for many other species of plants 

and animals

➢ Seedlings spread by ocean currents

➢ Salt exclusion ability

Rhizophora mangle L. (red mangrove) leaves,

flowers, and viviparous seeds.
Guide To The Ecological Systems Of Puerto Rico

197

Box 23. continued

The red mangrove gets its name from its reddish bark. Certainly the most

obvious feature of red mangroves is their characteristic highly branched stilt or

prop roots. These are not true roots. They are adventitious, that is, their origin

is in stem tissue. The stilts appear to be “tree legs,” thus they are sometimes

called a walking forest. Very often these forests are at the water’s edge, growing in very silty and anaerobic conditions. These trees can exchange oxygen

via large and numerous lenticels on the stilt roots. They can exclude salt by

concentrating cell sap and preventing salt uptake with water uptake from soil. 

High leaf fall rates add high quantities of biomass to the forest floor. The

leaves and other organic matter from the forest are the basis for a detritally

enriched food chain that ultimately yields some of the highest secondary

productivity known. Up to 80 percent of all harvested fish and associated

shellfish species in tropical coastal waters spend all or part of their life cycle

associated with mangrove swamps. They are the ecological equivalent of salt

marshes in the temperate zone and are truly nursery areas for a vast assemblage of animal species.

Red mangroves produce yellow star-shaped flowers and shiny leathery

evergreen leaves. When mature and reproducing, their seeds germinate while

still attached to the adult parent tree. This condition is called vivipary and is

quite rare in the plant world. When mature, the young seedling drops and is

most often spread by ocean currents. Some of the bayonet-shaped seedlings

may stick in the mud if the tide is out. The seedlings may be more than 1 foot

in length, with the first root (radicle) the bulk of its growth.

Red mangrove trunks are frequently used for posts or charcoal production.

The bark is a commercial source of tannin for leather tanning. Fringing forests

on windswept coasts may only be 10 meters (33 feet) tall, whereas in optimally protected areas they may grow to 50 meters (164 feet). They rarely exceed

20 meters (66 feet) in Puerto Rico.

For more information on this species, see Hogarth 1999, Jiménez and

Lugo 1985, Little and Wadsworth 1964, and Tomlinson 1986.
General Technical Report IITF-35

198

Box 24. Avicennia germinans L. (black mangrove) 

Another mangrove important to the 

Neotropics is Avicennia germinans L.

(black mangrove). It is not as easily 

distinguished as Rhizophora mangle

L. (red mangrove), because it does not

exhibit the easily recognized adventitious stilt (prop) roots or its red bark.

This species does have an easily recognized morphological feature, that is, its

pneumatophores (see below). They are

vertical upward root growths that aid in

gas exchange. This species is also ecologically very important. Black mangroves appear in coastal swamp forests

throughout the New World tropics from

the Gulf coast of the United States and

Mexico, throughout the West Indies and is present on both the Pacific and

Atlantic coasts of Central and South America (northern Perú and southern

Brazil). Its leaves are oppositely arranged, elliptic, leathery, and yellow-green

(see above). The leaves are salty to the taste. Its bark is dark, thus its common

name, and fissured when old.

It grows in brackish to hypersaline waters and can grow in soils where

salinities range from 0 to 100‰. In hypersaline conditions, individual trees

may be stunted. In all saline habitat conditions, the plant is adapted to excrete

salt through specialized glands on its leaves. Depauperate forms are best

observed in depression areas away from the coast where high tide or storm

water can be trapped producing hypersaline conditions. It also grows well in

dry habitats. It grows best in wet riverine habitats and may achieve heights of

30 meters (98 feet) in Central America, whereas in Puerto Rico maximum

heights rarely exceed 15 meters (49 feet). Throughout most of its range it will

be found growing in a mixed mangrove forest. It, too, adds greatly to the detritally enriched food chain that enhances the complex food web associated with

mangrove ecosystems. This results in the production of many commercially

important species of mollusks, crustaceans, and numerous fish. Just as in red

mangrove, natural monoculture black mangrove forests also occur. It is limited

The leaves, stems, flowers, and fruit of

Avicennia germinalis L. (Black mangrove)
Guide To The Ecological Systems Of Puerto Rico

199

Box 24. continued

in its distribution by frost. It grows

best in full sunlight and will have

reduced stature in a mixed mangrove forest.

Black mangrove is also viviparous in that its seeds germinate

while still in the fruit (capsule) 

and attached to the parent plant. 

The tree’s flowers are small spikes

with individual white-yellow 

flowers. Flower-ing can take place

throughout the year. Initially four

eggs are formed, but three abort

early and only one fully develops

into a one-seeded fruit. Trees will

produce hundreds of fruits per year.

As in the case with red mangroves, black mangrove seedlings drop and are

vectored by tidal change and currents. The seedlings need to locate above the

low tide mark in the littoral zone. Sexual maturity is reached when the tree

grows to about 3 meters (10 feet).

One of the most interesting morphological features exhibited by black

mangroves is their root development. They produce a shallow sinker root system typical of most plants that grow in wet areas. Avicennia germinans may

also produce slender adventitious roots from their trunks up to 25 centimeters

(1 foot) long. Pneumatophores are also produced growing vertically up from

horizontal lateral roots in the substrate. Pneumatophores are small, pencil-like,

vertical, upward extensions that serve in gas exchange. There may be hundreds

of them under one tree and their height differs with that habitat’s water depth.

Up to 65 percent of a tree’s total biomass may be in roots. Because of their

extensive root systems, they are considered soil stabilizers along coasts and

rivers. 

Black mangrove is easily damaged by exposure to auxin-based pesticides,

strong winds (especially hurricane strength), and alteration of its hydrological

conditions. In September 1998, Hurricane Georges produced winds of 145 to

160 kilometers per hour (90 to 100 miles per hour), with gusts nearing 242

kilometers per hour (150 miles per hour). Most of the black mangroves in the

The pneumatophores of Avicennia germinans L.

(black mangrove) growing on the south coast of

Puerto Rico 

G. Miller
General Technical Report IITF-35

200

as 0.6 meter (2 feet) in its first year. Mangroves sometimes root in mud lacking

oxygen, so they send out aerial prop roots that allow for the exchange of gases

required for respiration. Gradually this tree can form its own colony of mangroves.

The term mangrove can also refer to an ecological community type such as

mangrove swamp, which may include trees, shrubs, herbs, ferns, and epiphytes in 

a complex mangal ecosystem. Mangrove communities are notable for their species

diversity, salt tolerance, ability to colonize coastlines, and very high biological 

productivity. Life in a mangrove ecosystem is in a constant state of flux owing to

changes produced by natural processes and increasing human interactions. Some

human activities such as shrimp pond construction have resulted in vast areas of

mangroves being destroyed, which is ecologically catastrophic.

Mangroves exhibit a series of adaptations that allow them to hold their positions in the coastal fringe. They include:

➢ Tolerance to high amounts of salt

➢ Specialized roots that allow them to establish in soft muds or saturated

conditions

➢ Seeds that can germinate on the tree (viviparous) and when they fall, the 

seedlings can float

➢ Special structures that permit gas exchange in low oxygen environments,

such as lenticels, aerenchyma tissue, and pneumatophores

Ecological Functions of Mangroves

Only recently have we been able to understand the complex mangrove ecosystem. 

We know that red mangroves provide a safe wildlife habitat both on land and

around their prop roots in the water. They also dampen the power of storm waves.

Box 24. continued

Boquerón Wildlife Refuge were blown over because they produce a ball root

system, whereas the red mangroves, with their prop roots, were only minimally damaged. Black mangrove wood is used for charcoal production and firewood in developing countries. It also has a variety of other uses such as posts,

power poles, framing, railroad ties, pulp, and fiberboard. Its bark yields tannins and medicinals. Cooked seedlings can be eaten, and its leaves can be used

as a source of salt.

For more information on this species, see Jiménez and Lugo 1985, Little

and Wadsworth 1964, and Lugo and Snedaker 1974.
Ta

ble 19

—

Ta

x

o

n

o

mic, m

orp

h

olo

gic

al, re

pro

d

u

ctiv

e, a

n

d

h

a

bitat c

o

m

p

aris

o

n

s

of th

e fo

ur s

p

e

cie

s

of m

a

n

gro

v

e in

P

u

erto

Ric

o

Scientific name Morp

hological an

d

an

d family

Com

mon

names reprod

uctive features Habitats

Rhizophora mangle L. Red

man

grove Viviparous Soft to firm organic m

u

d

Rhizop

horaceae mangle rojo Aerial stilt roots from

branches an

d tru

n

k

Occupies outer tidal frin

ge, b

ut can ap

pear in

(man

grove family) Leathery leaves op

posite, elliptical, an

d transitional areas an

d ex

hibit d

warfin

g

Pantropical family an

d

glabrous Grows best in areas of daily tidal chan

ge or

gen

us Stip

ules present in riverine habitats

Black

dots on

bottom surface H

urricane resistant owin

g to stilt roots

Yellow flowers in foursFruits olive greenLarge lenticels present on stilt roots

Trees up to 30 meters (98 feet) tallRed roots an

d stems

Avicennia germinans L. Black

man

grove Viviparous (not ob

vious) Occupies diverse habitats from frontal

Avicen

niaceae (black

mangle negro Aerial root p

neu

matop

hores frin

ge to back frin

ge an

d

h

y

persaline

man

grove family) Leaves op

posite an

d ovate to elliptic elevated

basins

Monogeneric family

Bottom of leaves hairy an

d

gray

May

be heavily

damaged

durin

g

h

urricanes

Pantropical family an

d Salt-excretin

g

glan

ds on leaves because top

heav

y (balloon

gen

us Bark

gray-black effect); they

produce a root ball;

Petiole without glan

ds At Boq

uerón

Refu

ge, the black

man

groves

May

grow as tree or shru

b

were top

pled in

H

urricane Georges in 1998.

Trees rarely taller than 20 meters (66 feet) Flowers produce ab

u

n

dant nectar used

b

y

W

hite flowers in terminal spikes bees for honey

production

Fruit sin

gle-seed capsule

Laguncularia racemosa W

hite man

grove Viviparous (not ob

vious) Fou

n

d in the lan

d

ward side of the frin

ge,

Gaerth. mangle blanco Facultative p

neu

matop

hores althou

g

h

may form

p

ure stan

ds in

Com

bretaceae Leaves op

posite an

d somew

hat flesh

y

disturbed sites

(Com

bretu

m family) Bottom of leaf without hairs, with

pits at Sites are usually elevated

with lower tidal

minor veins freq

uency (in riverine systems)

Petioles red

with a pair of glan

ds near base Grow in low

depressions; may

grow in

peat

of leaf an

d soft m

u

d

Leaf elliptic shape with apex in

dented,

glan

dular at the base

Bark fissured an

d

gray

Inflorescence panicle of racemes with

bellshaped

w

hite flowers

Gray-green fruit, sin

gle-seed

n

utlet

U

p to 13 meters (40 ft) tall

Guide To The Ecological Systems Of Puerto Rico

201
General Technical Report IITF-35

202

Ta

ble 19

—

Ta

x

o

n

o

mic, m

orp

h

olo

gic

al, re

pro

d

u

ctiv

e, a

n

d

h

a

bitat c

o

m

p

aris

o

n

s

of th

e fo

ur s

p

e

cie

s

of m

a

n

gro

v

e in

P

u

erto

Ric

o

c

o

ntin

u

e

d

Scientific name Morp

hological an

d

an

d family

Com

mon

names reprod

uctive features Habitats

Conocarpus erectus L. B

utton

wood

Leaves alternate Brackish to fresh

water com

m

u

nities inlan

d,

Com

bretaceae man

grove Pits alon

g

main

vein on

bottom surface of althou

g

h

present on

dry ex

posed

(Com

bretu

m family) mangle botón leaf limestone cliffs in

G

uánica Forest w

here it

May

have hairy leaves forms a hig

hly sheared old-growth forest

Petiole with

pair of glan

ds at base of blade rarely over 0.5 meter (2 feet) tall an

d

Often

grow as shru

bs growth is prostrate over the surface

Bark rou

g

h

Tolerant of hig

h salinity

Some call this a man

grove associate May

grow on san

d

y

berms as a beach shru

b

because it lacks vivipary an

d aerial roots, or small tree

Flowers terminal, globose headsFruit an ag

gregate of n

utlets, rou

n

d an

d

p

urplish-brow

n

U

p to 6.5 meters (20 ft) tall
Their prop roots stabilize land that would normally be eroded into the sea. William

Odum (1969) demonstrated that the mangrove is actually the basis of an elegant

detritus-based food chain supporting numerous tropical animals.

Mangroves produce a tremendous amount of leaf biomass each year, which

they shed. The red mangrove in particular, has been shown to produce almost 3

tons (2.72 metric tons) of leaves per 0.4 hectare (1 acre) per year. This rate of biomass formation is equal to that of intensively cultivated agricultural lands and only

slightly lower than that produced by coral reefs, marine seagrass beds, and tropical

rain forests. This leaf biomass is the origin of the mangroves’ unique and vital

detritus-based food chain.

Bacteria and fungi begin to colonize the leaves while they are still on the tree.

Within about 24 hours after the leaf falls, marine microbes invade the waxy cuticle

of the leaf. These microbes stay on the leaf 2 or 3 weeks, or until the particular 

cellular nutrients they thrive on are exhausted. They coexist with, and are at times

succeeded by protozoans, bacteria, and various fungi. In looking at the leaf with 

the naked eye, these bacteria and fungi look like a brown slime. It is this slime that

attracts other marine animals, mostly marine worms and microscopic crustaceans

called copepods. Small crabs and amphipods are soon drawn to the leaf by these

worms and copepods. The worms, crabs, and amphipods also break down and 

consume the leaves.

The broken down leaf particles are called “detritus.” This detritus can be eaten

and excreted and eaten again by many different animals; mainly small mollusks,

crustaceans, shrimp, sea worms, and crabs. Those animals then become prey for

small fish, which are then eaten by larger fish. Many of those larger fish are commercially important for human food (protein). One commercially important fish,

the striped mullet, feeds directly on mangrove detritus.

It is estimated that 75 percent of game fish and 90 percent of commercial

species in Florida’s waters depend in part on the mangrove ecosystem. There are no

printed figures on the importance of mangroves to commercial game fish in Puerto

Rico, but it is likely that they are at least as high as in Florida. Mumby et al. (2004)

indicated that mangroves in the Caribbean strongly influence the community 

structure of fish on neighboring coral reefs. In addition, biomass of commercially

important species is more than doubled when adult habitat is connected to mangroves.

Habitat zonation for plants and animals living in the mangrove is very striking. 

There are three distinct zones:

➢ Branches of the trees

Guide To The Ecological Systems Of Puerto Rico

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➢ Terrestrial roots

➢ Submerged roots

The branches above the water line provide an excellent rookery for birds. Two 

birds, the golden warbler and the mangrove clapper rail, are true mangrove species

(endemics). Other birds such as the cattle egret normally only roost in mangroves.

Their flocks can be observed migrating daily to and from inland agricultural lands

at dusk and dawn. The branches of the tree are structured as if the tree were an

apartment building; with the larger birds like the egrets, herons, pelicans, cormorants, and frigate birds using the top of the canopy, and smaller birds using the area

inside. The advantage of these island rookeries is that they offer protection from

egg-robbing rodents and humans.

The terrestrial roots are dominated by mobile animals such as crabs and mollusks. A few examples of these are the Littorina angulifera (red snail), Grapsus

grapsus, Aratus pisonii, Goniopsis cruentata (crabs), and Cardisoma guanhumi

(the edible land crab). Throughout a mangrove swamp, large brown termite nests in

the aerial branches can be seen. These are the nests of Nasutitermes costalis, which

harvest the dead wood in the swamp. Other groups present are ants, spiders, moths,

roaches, and mosquitoes. Lizards will likely be present feeding on these invertebrates.

The most densely populated and species-rich area in the red mangrove swamp

is the habitat created by prop roots that penetrate the water of the subtidal zone

(fig. 59). A wide variety of plants and animals form biological coatings that cover

these roots and serve as food and refuge to many animals. The presence of these

organisms may provide some protection from predatory root-boring animals.

Rützler and Feller (1996) indicated a number of new species recently described

from these fouling communities. They estimated that perhaps as many as 20 to 30

percent of the microbes, algae, sponges, and worms living on their research mangroves may be as yet undiscovered species in Twin Cays off the coast of Belize.

Underwater mangroves offer a veritable cornucopia of organisms to observe. In

the narrow channels between the roots, are found green algae, jelly fish, the spotted

cucumber, and the young of many fish. The submerged roots represent the least

understood, but probably the most interesting zone (fig. 60). It is here that competition for living space is the greatest. Most of the sedentary animals are filter feeders.

Algae are also present, but only to depths where light penetrates. Among those

algae found on submerged roots are Caulerpa mexicana Kuetzing (green feather

alga), C. racemosa (Forsskal) J. Agardh (grape alga), and Acetabularia crenulata

Lamouroux (mermaid’s wine glass). Other benthic algae present in the lighted
channels are Penicillus capitatus Lamarck (shaving brush alga), Halimeda opuntia

(L.) Lamouroux (coralline watercress alga), Valonia ventricosa J. Agardh (sea

pearl), Udotea flabellum (Ellis & Solander) Lamouroux (hard fan alga), and

Avrainvillea nigricans Decaisne (soft fan alga).

For additional details see the description of the littoral fauna, by Matthews

(1967).

Zonation of Mangrove Communities

Mangroves have been estimated to dominate about 75 percent of the world’s coastlines between 25° N and 25° S latitude. Mangroves are classified structurally many

different ways. Lugo and Snedaker (1974) classified mangroves into five categories

according to the geomorphology of their basins:

➢ Riverine mangroves grow on river flood plains and are involved with the 

lateral flow of water of low salt concentrations.

Guide To The Ecological Systems Of Puerto Rico

205

Figure 59—The prop roots of Rhizophora mangle L.

(red mangrove) on south coast of Puerto Rico. 

A.E. Lugo
General Technical Report IITF-35

206

➢ Basin mangroves grow in depressions where waterflows are sluggish 

and the vertical flow of water prevails over its lateral flow.

➢ Fringe mangroves grow at the edge of the sea or other water bodies 

and are exposed to vertical water fluctuations or to broad wave fronts.

➢ Mangrove islands occur out at sea as overwash islands where tides 

flow over the islands or may develop inland as mangrove “hammocks”

where water flows around the island.

➢ Dwarf red mangroves occur in humid areas over peats. The trees are

dwarfed but have leaves of normal size. Mature trees of dwarf mangroves are not to be confused with scrub mangroves, which have 

reduced size as a result of harsh growing conditions such as 

hypersalinity.

Each of these different types of mangrove demonstrates a different set of environmental conditions that shape the landscape, and what types of flora and fauna

will be present and what types of environmental stressors will have an impact.

Stressors will be mentioned later.

Lugo and Cintrón (1975), classified Puerto Rican mangrove communities into

two general categories: south coast and north coast types. The determinant factors

in this classification were the intensity of wave action, rainfall, and freshwater

runoff.

The environment of the south coast type mangrove forest is characterized by

low rainfall, very little freshwater runoff, and a low wave energy regime. The 

predominant type of forest is the fringe mangrove forest. In general, south coast

Figure 60—Vertical zonation of organisms along the underwater prop roots of Rhizophora 

mangle L. (red mangrove).
fringing mangroves grow at the edge of the sea, have low structural complexity,

low leaf fall, and low rates of tree growth. These forests are dominated by the

Rhizophora mangle L. (red mangrove). The salt content of the south coast waterways (i.e., ocean, lagoons, and others) varies little throughout the year. North coast

type mangroves on the other hand, show higher structural complexity and higher

rates of leaf fall and tree growth. The salt content also fluctuates more in the waterways on the north coast than on the south owing to seasonal terrestrial freshwater

runoff.

Lugo (1978) came to the conclusion that the smaller the mangrove, the higher

the salinity of the environment. He found a rapid increase in mangrove tree mortality beyond a soil salinity threshold of about 65 ‰ (parts per thousand). Through

this conclusion, Lugo has come up with another way of classifying mangroves, that

is, through their succession rates. According to Lugo, in the American tropics the

mangrove swamp forest consists of a series of zones each dominated by one

species of mangrove. From open ocean and extending through to the area covered

by maximum high tides, the red mangrove is dominant. Except for the red mangrove’s prop roots and its seedlings, this forest floor is devoid of higher plant life.

Vigorous growth of more red mangroves at the edge of the forest results in restriction of water circulation to the inner parts of the swamp. These areas can then be

invaded by the more salt-tolerant black mangrove. Eventually, extensive areas of

the inner swamp die, and a salt flat is formed. Lugo is quick to point out that

severe storm or wave fronts could delay this succession indefinitely.

Although there is some animal life in the above-water parts of all mangrove

forests, it is not abundant. Where the roots are submerged, massive epifauna

populations are numerous.

Extent of Puerto Rico’s Mangroves

Puerto Rico may have had 12 146 hectares (30,000 acres) of mangroves at the time 

of European discovery. By 1975, half had been destroyed. Much of the loss was

associated with agriculture and a variety of human developments along the coastal

fringe. By the mid 1980s, up to 75 percent of Puerto Rico’s mangroves had been

destroyed or highly altered. Naturally, most of the loss since 1975 was associated

with continued development of the coast. Figure 61 shows the distribution of mangroves in Puerto Rico (see app. 2).

Mangroves are recovering in some places in Puerto Rico as a result of their

protected status. In the last few years there has been a net gain in mangrove coverage. The Department of Natural and Environmental Resources of Puerto Rico 

Guide To The Ecological Systems Of Puerto Rico

207
General Technical Report IITF-35

208

Figure 61—Distribution of mangroves in Puerto Rico. Modified from an unpublished map by the Puerto Rico Department of Natural and Environmental Resources.
currently estimates mangrove coverage at 9020 hectares (22,300 acres), distributed

in 119 habitats. Twelve of these habitats are considered critical because of collateral construction, recreation or tourist activities, and urbanization. Their total coverage is 2196 hectares (5,425 acres). One of these is the mangrove complex surrounding the Phosphorescent Bay at La Parguera (see app. 2 p. 377). Mangroves

compose a significant portion of Puerto Rico’s public forests (see section on Puerto

Rico’s Commonwealth Forests). These forests have exceptional educational, recreational, and food value. Mangroves constitute both a wetland species and a wetland

habitat. Today, permits are required to alter them in either case. They are covered

by a variety of federal and Puerto Rican regulations that generally require permits

to be issued prior to activities such as dredge and fill in mangrove habitat (see section on wetlands). Having said this, mangroves are still being damaged and

removed largely because of ignorance of their ecological importance and of the

law. Law enforcement is also limited.

Stressors

Lugo et al. (1981) described a stressor as any factor or situation that forces a

system to mobilize its resources and spend more energy to maintain homeostasis.

Lugo later said that “when all conditions are equal in the environment, ecosystem

response to a stressor depends on the point of attack of the stressor on the system

. . . and that if the stressor had interfered with the primary energy source of the

mangrove system, recovery would be slow.”

Factors that can produce stress in mangroves include:

➢ Low temperature ➢ Runoff

➢ Low nutrients ➢ Allochthonous inputs of pollutants

➢ Low O2 concentrations ➢ Changes in salinity

➢ High wind ➢ Changing depth

➢ Drought ➢ Water temperature

➢ Storms ➢ Pesticides

➢ A rise in sea level ➢ Oil spills

➢ Predators ➢ Human stressors

Lugo has classified stressors into five types:

➢ Those that alter the nature of the main energy source

➢ Those diverting part of the main energy source before it can be 

incorporated into the system

➢ Those that remove potential energy before it is stored, but after it 

is transformed by plant photosynthesis

Guide To The Ecological Systems Of Puerto Rico

209
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➢ Those that remove storages, either in photosynthesis or in the 

ecosystem itself

➢ Those that increase the rate of respiration

One stress that the mangrove swamp has to endure is abnormal runoff. When 

a portion of land is developed bordering the mangrove swamp, increased rainwater

runoff causes problems. What was once water-thirsty soil is now water-repellent

pavement. The runoff washes more nutrients, pollutants, and sediment into the

water. The extra nutrients result in increased algal growth that can directly clog the

mangroves’ “gas exchange” lenticels. Increased sediment may build up until it

eventually forms a smothering black blanket that kills the trees.

Another stressor is the wood-boring isopod, Sphaeroma terebrans, which

destroys the prop roots of mangroves, especially those of the red mangrove.

Sphaeroma enters the prop roots of the mangrove. Reproduction then occurs inside

the roots, with the young passing through all developmental states within the root.

These young isopods then join the adults in wood boring. In time, in highly infested areas, all prop roots of the outer fringe of the mangrove colony are destroyed.

This is as far as the isopod goes in destroying the tree, waves then take over, causing the tree to topple over.

Herbicides and insecticides are also stressors on mangroves. The amount of

herbicides required to kill mangroves appears to be smaller than that required to

kill other species of tropical trees. With application of as little as 1 percent of a herbicide, a 90-percent defoliation occurred in the mangroves after 1 month. Walsh et

al. (1973) demonstrated the effects of herbicides and concluded that the mangrove

was affected so extremely because, although the herbicides were applied to the

bark of the tree, tides and storm waves washed them down near the prop roots,

where the herbicides did their greatest damage.

Oil is another stressor. On March 17, 1973, the Greek tanker, the Zoe

Colocotroni, spilled about 5,000 tons (4535.92 metric tons) of oil in the southwestern tip of Puerto Rico on Margarita Reef near Bahía Sucia. Wind and water

currents pushed oil into the fringing mangrove forest of the bay, covering significant areas of mangrove forest. Mangroves are very sensitive to oil spills because 

of the dependency on their prop and aerial roots for respiration. The response of 

the mangrove to oil is a very rapid shedding of leaves, which then leads to the 

new leaves being susceptible to deformation and insect attacks.

A significant legal outcome was associated with this oil spill. In 1980, a U.S.

Court of Appeals found that states and Puerto Rico had the right to sue and recover

damages to their natural resources even though there was no apparent market value
(to the mangrove swamps). In addition, it was ruled that the $2.1 million awarded

in 1978 to Puerto Rico had to be used for land acquisition of comparable ecological

value for establishment of a public park. This was the beginning of the establishment of the Cabo Rojo National Wildlife Refuge that rings Bahía Sucia today.

Mangrove stressors produced by humans can be grouped based on severity of

impact and likelihood of reclamation. Figure 62 expresses these on a sliding continuum with the top line being most severe and least reclaimable because they alter

the habitat’s soils and hydrology. Those on the bottom line are generally less severe

and through natural regrowth or succession, are able to recover on their own.

Mangrove swamps and associated marshes in the San Juan area are newly

incorporated into the U.S. Environmental Protection Agency’s (EPA) San Juan 

Bay National Estuary Program. This is the only tropical ecosystem in the U.S. 

EPA Estuary program and the only one outside the continental United States. This

complex estuary is a mosaic of marine and coastal ecosystems located in the San

Juan metropolitan area. Many of its components have been destroyed or severely

degraded. This new program, completed in October 2000, is designed to restore

and conserve its present components. At its center is the Comprehensive Conservation and Management Plan, which involves local, state, and federal agencies, 

Guide To The Ecological Systems Of Puerto Rico

211

Figure 62—Effect of human stressors on mangroves.
General Technical Report IITF-35

212

as well as citizens, educators, and private groups. The plan has 49 action plans that

address four priority areas:

➢ Water and sediment

➢ Habitat, fish, and wildlife

➢ Aquatic debris

➢ Public education and involvement (EPA 2000)

Values of Mangroves

Until the latter half of the 20th century, most people looked on mangroves as 

“junk” trees as they seemed to have little value except for charcoal production, as

building or wharf posts, and as a source of tannins. Today we know that they are

very valuable. Tables 20 and 21 list some of the many benefits derived from 

mangroves.

Tropical societies have been using wetlands for millennia, both directly and

indirectly. Mangroves have been economically important throughout history, but

unfortunately the values of mangroves have not been accounted for monetarily

until recently. We now know they are worth millions of dollars per year. More and

more of the human population (65 percent) live in the world’s coastal zones, and

that number is expected to grow significantly in the next 50 years. In the

Caribbean, it is estimated that 85 percent of the population lives in the coastal

zone. Coastal zones have not been well managed up to this point. It is incumbent

upon us to recognize what is at risk when this exceptional ecosystem is being

degraded.

Destruction of vast areas of mangrove ecosystems, with from 50 to 60 percent

of all mangroves destroyed, is occurring in the tropical world. Currently, mangrove

destruction is estimated to be 5 percent annually worldwide. Much of the recent

destruction has been for the construction of industrial shrimp farms. Over 202 425

hectares (500,000 acres) were destroyed in Ecuador for this purpose. Once

destroyed, all of these direct and indirect values that societies derive from mangroves are lost, maybe forever. In addition, locals do not benefit from mangrove

conversion because most of the high-quality shrimp protein is largely exported to

the United States or other industrialized countries. Developed nations are unwittingly putting great pressure on many natural ecosystems as the demand for highgrade products at low cost increases. Awareness is needed at both ends of this supply/demand system so the remaining 50 percent of this extremely beneficial and

productive ecosystem is not destroyed.
Table 20—Economic values of mangroves

Activity Use

Agriculture Direct grazing or biomass gathered for fodder

Construction Scaffolding, posts, pilings, railroad ties, and tool handles

Ecotourism/ Growing interest in using mangroves for water-related field trips, 

education recreation, and education

Fishing Net floats, poles, and fish harvest

Food Honey, alcohol, bark condiments, consumption of fruits and secondary 

animal products (birds and eggs)

Fuel Firewood and charcoal

Household Water pipes, furniture, and dyes

Medicine Bark, leaf, fruit decoctions, and incense

Guide To The Ecological Systems Of Puerto Rico

213

Table 21—Ecosystem values of mangroves

Activity Value

Detrital-based food chains Low direct use results in high secondary productivity 

through detrital enrichment

Ecosystem linkage Proximal to other high-productivity ecosystems (coral 

reefs and seagrass beds)

Education/research Exceptional habitat to explore productivity, symbiosis, 

food chains, competition dynamics

Nursery habitat 80 percent of commercially harvestable fish and shellfish 

spend part of life cycle here

Nutrient filter Controls eutrophication

Sediment filter Keeps water column clean

Storm buffer Reduces impact on inland natural and human systems

Waste treatment Effective in filtering and using human wastes

Wildlife habitat High value as rookery for various shore and marine 

birds, small fish, and other marine organisms

Riverine Estuaries

Mangrove swamps, the lowland reaches of rivers, coastal lagoons, and bays 

are examples of Puerto Rico’s estuaries. In all these places, upland freshwater

runoff reaches the coastal lowlands where it mixes with seawater. An estuary is

the zone where seawater and freshwater mix; the salinity area is lower than in

the ocean, but higher than in freshwater. Estuaries are dynamic systems, and the

location of the mixing zone changes year round owing to changing conditions

of freshwater runoff and tidal energy. If rainfall is abundant, the salinity of the

estuary decreases. Salinity increases if there is a drought or during periods of

ocean storms and high waves and tides.

We already discussed mangrove forests as examples of estuaries. In this

section, our focus is on riverine estuaries. Riverine estuaries are the zones
General Technical Report IITF-35

214

where freshwater and saltwater mix within the river channel. However, riverine estuaries include the mangrove flood-plain forests (riverine mangroves), 

which occur on both sides of the channel of rivers. In these flood-plain forests

Pterocarpus officinalis Jacq. (swamp bloodwood) and other tree and fern species

can also be found among the mangrove trees. They all become part of the riverine

estuary.

During intense rainfall, rivers and aquifers overflow, and their discharge overwhelms saltwater intrusion such that most coastal systems have a freshwater layer.

At this time, it is common to see freshwater plants floating in the ocean. However,

sediments of rivers, swamps, or lagoons will contain saltwater buried by the weight

of the freshwater column. In contrast, during the dry season, both river and aquifer

discharges into the coast reach minimum values. Without a freshwater discharge to

impede movement of sea water powered by tides, saltwater wedges push upstream

and into bays, swamps, and lagoons and become saltwater systems. Saltwater

wedges penetrate several kilometers inland through river channels. The limit of

penetration is determined by the topography of the channel relative to the push of

the tide. At peak dry season, a sandbar closes the mouth of many rivers (fig. 63).

River discharge becomes a trickle, and the river estuary appears to be a lake in the

flood plain. Heavy river discharges remove the sandbar following the onset of

heavy rains during the wet season. At this time, the cycle of salinity change of the

estuary starts again.

The changes in salinity and water movement through these estuaries—rivers,

swamps, bays, and lagoons—drive the biota and ecological processes of estuaries.

Species that live in estuaries have to survive wide fluctuations in salinity, water

current, water depth, or combinations of all three. Many only visit the estuary when

conditions are favorable for them. For example, marine organisms enter the river

when salinities are high. Freshwater organisms visit the estuary when salinity is

low. Others migrate in and out of the estuary according to their tolerance. Mangrove

trees can survive the wide fluctuations of water and salinity in the swamp, but

when conditions exceed their adaptations, they die massively.

This in- and outmigration of so many species makes estuaries very dynamic 

systems. Estuaries are known for high primary productivity, abundance of food for

animals, and as a place where many types of organisms find optimal conditions for

reproduction and development. In Puerto Rico, about 11 species of freshwater crustaceans, mollusks, and fish migrate from high-elevation streams to estuaries where

they develop. These organisms require saltwater conditions to complete their life
cycles. Similarly, open ocean fish enter estuaries to reproduce and complete the

early stages of their life cycles. The estuary provides protection and abundant food.

An example of a marine organism that reproduces and feeds in the estuary is

the tarpon (Megalops atlanticus). This is a commercially important fish, favored by

sports fishermen. Freshwater shrimp (fig. 64) are examples of montane organisms

that float eggs and larvae to the estuary where they develop and then migrate

upstream to montane habitats in stream pools. The upstream migrations are massive

and subject to heavy predation by fish, birds, and people. Caribbean freshwater fish

dominate the lower inner systems. Some of the same species will also be found in

high-elevation freshwater streams.

Through research, fascinating facts about the ecology of the movement of these

species are emerging, and these findings help us manage aquatic systems and water

extraction from rivers. Below is a summary of the findings:

➢ Most aquatic organisms, particularly shrimp, are many times more 

abundant (even orders of magnitude more) at night than during the day.

➢ Even the drift of larvae and eggs to the estuary and the postlarval 

migration upstream follow a diurnal rhythm with greater numbers 

moving at night. At 1:00 p.m., the average downstream flow of larvae

peaks.

Guide To The Ecological Systems Of Puerto Rico

215

Figure 63—Typical mouth of an island river during the dry season. Notice the sand bar that forms

and prevents freshwater discharge to the ocean. The river mouth is an estuary with a saltwater

wedge that moves inland several kilometers depending on topography and tidal conditions. 

A.E. Lugo
General Technical Report IITF-35

216

➢ Forty-two percent of shrimp larvae floating downstream are lost to 

intake pipes. Adjusting water intake to the schedule of larval and 

shrimp migrations, can greatly reduce loss of shrimp larvae and 

juveniles.

➢ River dams, even small ones, impact migrations and species 

composition upstream from the structures.

➢ Dead leaves from the forest (detritus) are an important food source for

aquatic organisms in the river and estuary.

➢ Stream discharge, particularly large discharges, trigger migrations.

Droughts affect the food webs in the river, particularly in pools.

➢ Conditions in pools influence the degree of reproduction of riverine 

fauna.

➢ Shrimp activity controls algae growth in the river and keeps rocks free 

of algal growth, which in turn increases safety to people using rocks to 

step across the river, as rocks are less slippery without algae. In fact, in 

the absence of shrimp, the species of algae change, as does the benthic

community and its functioning.

The importance of healthy streams to a modern society transcends the water 

supply and sewage dilution services. Many values are derived from these systems

including recreation, as well as aesthetic values. The population of Puerto Rico

understands the value of natural systems. A study by González Cabán and Loomis

(1999) found that Puerto Ricans were willing to pay up to $21 per year for maintaining the river-estuarine complex in the northeastern section of the island in

Figure 64—Freshwater shrimp (Xiphocaris elongata). 

J.G. Marsh
healthy condition. This translated to a $110 million value to the economy of Puerto

Rico.

Posters that illustrate the complexity and biodiversity of the riverine estuary are

available through the library of the International Institute of Tropical Forestry of

the USDA Forest Service in Río Piedras.

For further reading, see Benstead 2000, Benstead et. al 1999, Benstead et. al

N.d., Johnson and Covich 2000, March et. al 2001, March et. al 2002, Pringle

2001, and Scatena and Johnson 2001.

Guide To The Ecological Systems Of Puerto Rico

217
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Chapter 6: Marine Ecosystems

Submerged Seagrasses

In the shallow coastal sublittoral zone of Puerto Rico’s bays, coral reef lagoons, 

and mangrove channels, soft marine sediments are frequently covered with a lush

growth of submerged aquatic vascular vegetation (SAV). These perennial herbaceous plants are all adapted to exposure to a variety of saline and substrate conditions. There are 5 families, 12 genera, and 58 SAV species distributed throughout

the world’s tropical and temperate waters. All are higher flowering monocot plants

(angiospermae). The majority of the tropical genera and species are found in

Caribbean and Indo-Malaysian waters but occur in all coastal areas of the world,

except Antarctica. Their distribution is affected by a variety of factors including

depth, salinity, water turbulence, temperature, and turbidity.

The habitat these organisms form is classified as a marine aquatic bed wetland

according to the Cowardin et al. (1979) Classification of Wetlands and Deepwater

Habitats of the United States. Often intermingled in the seagrass beds will be macrobenthic algae, a few coral, and a wide variety of animals, many of which will be

epiphytic. Ecologically, this community of plants and animals constitutes one of the

most productive ecosystems on Earth (table 22). It forms a rich food web with hundreds of species of organisms that use seagrasses as physical substrate and food

and serves as part of the complex coastal nursery for many fish and invertebrates

that breed and develop in these waters. The values of these seagrass ecosystems

include:

➢ Direct grazing by herbivorous predators

➢ Detrital enrichment of the food chain

➢ Nesting habitat for a variety of animals

➢ General habitat for an array of animals and other marine plants

➢ Predator escape for young, especially fish

➢ Stabilization of the substrate via large masses of interlocking 

rhizomes and roots

➢ Ability to dampen the intensity of storm waves

➢ Absorbtion of nitrogen and phosphorous

➢ Importance to the global carbon cycle

➢ Structural habitat for numerous epibionts

➢ Filtration of sediment from the water column

➢ Export of organic matter to other coastal ecosystems

➢ Source of human food

Guide To The Ecological Systems Of Puerto Rico

219
General Technical Report IITF-35

Table 22—Ratios of gross primary productivity (P) to aboveground standing crop (B) 

for mangrove forests, and for other systems that may succeed them

Aboveground Gross primary

Ecosystem biomass productivity P/B

g/m2 g/m2year

Riverine mangrove forest in Panama 27,921a 10,147b 0.36

Riverine mangrove forest in Florida 11,943b 8,760b 0.73

Fringe mangrove forest in Florida 7,933b 5,292b 0.67

Scrub mangrove forest in Florida 786b 1,022b 1.30

Subtropical moist forest in Puerto Rico 19,947c 11,972c 0.60

Tropical moist forests in Panama 36,320a 11,972c 0.45

36,800a 11,972c 0.32

Saltwater marsh in Georgia 3,321d 3,285d 1.56

Freshwater marsh in south Florida 2,100e 4,745f 1.47

Thalassia beds 600–5,660g 1,825–13,410g 0.32–22.0

Coral reefs 846h 3,285–13,870h 3.8–16.0

a Golley et al. 1975.

b Lugo and Snedaker 1974.

c Odum 1970.

d Crip 1975.

e Steward and Ornes 1975.

f

Bayley and Odum 1975.

g Odum 1971.

h Odum and Odum 1955.

220

Aquatic bed seagrasses develop best in shallow, low-energy, submerged sand flats

and bays. Most seagrass beds are found in depths less than 10 meters (33 feet).

They complete their entire sexual life cycle in seawater, and most are very adept 

at vegetative reproduction. Most species are well adapted to deal with wave action

and shifting sediments in that they produce grass-like linear leaves and an extensive system of rhizomes. The creeping rhizomes produce erect shoots with leaves

and roots at each node. The roots are adventitious. All species are clonal and rely

heavily on asexual reproduction. In addition, they have thin leaves with a high 

surface-to-volume ratio, and aerenchyma tissue with extensive lacunae (air space)

in their vegetative structures permitting rapid diffusion of gases. The high surfaceto-volume ratios provide for maximum diffusion of nutrients between leaf blades

and seawater, and maximum photosynthetic surface. The horizontal rhizomatous

stems anchor and absorb nutrients. Flowers of seagrasses are incomplete, that is,

separate male and female flowers, which causes cross pollination. Some species are

monoecious, whereas others are dioecious. Submerged aquatic vegetation differs

from algae in that it produces true flowers, fruits, and seeds; develops vascular

tissues, and has true roots. (For information on access to seagrass beds in Puerto

Rico, see app. 2.)
The predominant Caribbean seagrass is Thalassia testudinum Koenig1 (turtle

grass, box 25). Other important Caribbean seagrasses include Syringodium filiforme

Kuetzing (manatee grass, box 26), Halophila decipiens Ostenfield (sea vine), H.

engelmannii Ascherson (six-leaved seagrass), and Halodule beaudettei (den

Hartog) den Hartog (shoal grass). None of the “seagrasses” actually belong to the

true grass family Poaceae. They are grass-like in their external morphology, thus

the common name. They often form dense blankets, much like a grass lawn, as a

single species or in a mixed community. Most seagrass meadows are monospecific,

that is, greater than 60 percent of the meadows have only one species present

(Hemminga and Duarte 2000). They frequently are referred to as underwater meadows and, in fact, are grazed by a number of animals including sea turtles and manatees. The expanded surface area provided by the seagrass leaves, especially turtle

grass, provides substrate for attachment of macro- and microepiphytic algae, as

well as protistans, bacteria, and a variety of epifauna, that is, animals living on 

the leaf. These organisms are grazed by progressively larger free-swimming and

surface-dwelling meio- and macrofauna. In many instances, this epibiotic community is so abundant that its biomass exceeds that of the seagrass leaf and, in fact, it

may be difficult to see the leaf’s surface. Ballantine (1971) identified 65 epiphytic

algae on seagrass leaves in Florida. Although seagrass ecosystems are highly productive, as little as 5 percent of the accumulated biomass is eaten directly by herbivores. The remaining 95 percent eventually enters the detritus food chain. As seagrass leaves age, initial organic releases are most likely taken up by epibionts, and

later, when the leaf detaches and floats free, it will gradually break down into

smaller pieces and sink into sediments where bacterial breakdown is initiated. This

degraded leaf substrate with its microflora will then be used by a variety of benthic

detritus feeders. Some seagrass leaves float long distances and can even enter deep

water food chains. Blades of seagrasses have shown up on pictures from the Puerto

Rico Trench at a depth of 7860 meters (25,780 feet).

Of the 12 recognized genera of seagrasses in the world, 5 are present in waters

around Puerto Rico, with 7 species present from 4 families (table 23). Two of the

species, Halophila decipiens Ostenfeld (sea vine) and Ruppia maritima L. (widgeon grass), can grow in habitats that are brackish, and Ruppia can grow in freshwater. Thalassia and Syringodium are the most abundant and widely dispersed seagrasses in the sublittoral zone of Puerto Rico in the southwest, south, and east

coasts, where the shelf is broader and more protected. The largest and most dense

meadows are in shallow waters of 2 meters (6 feet) or less. Halophila decipiens

Guide To The Ecological Systems Of Puerto Rico

221

Continued on page 226.

1 See appendix 1 for Common and Latin names.
General Technical Report IITF-35

222

Box 25. Thalassia testudinum Konig (turtle grass) 

By far the most 

abundant seagrass

species in Puerto Rico

and the Caribbean is

Thalassia testudinum

Konig (turtle grass). 

This species gets its

common name from 

the fact that it is 

eaten by green sea 

turtles. The family

Hydrocharitaceae is a

family of 16 genera and 120 species of submergent and emergent fresh and

saltwater aquatic herbs. Only two of the genera are marine and both are found

in Puerto Rico. Members of the family produce separately sexed male and

female flowers. Flowering occurs in April and May. The leaves are produced

in clusters or whorls at numerous points along the stems, which are horizontal

and root-like rhizomes. The rhizomes act like roots to anchor the plant into the

soft sandy bottom, and they periodically break, thus serving as a way to asexually propagate the species. Vast clonal populations of turtle grass are found

throughout its range. Habitat coverage can be less than a meter square or up to

hundreds of square kilometers (square miles). Thalassia grows in mud, sand,

and broken shell accumulations. Storms may cause detachment of old leaves,

and large windrows of the leaves are often found cast upon beaches. The

leaves can be collected and used for mulch and fertilizer. General growth and

accumulation of turtle grass biomass is controlled by available light, water

quality, available nutrients, substrate composition, and wave action. In the

Caribbean, biomass accumulation in the water near La Parguera in southwestern Puerto Rico ranges from 532 to 1,986 grams per square cubic meter per

day, according to González Liboy (1979). This indicates very high productivity comparable to intensive high-yield agriculture. This is why this ecosystem

is so vital to the complex grazing and detrital-based food webs found there and

in all seagrass ecosystems. For a review of grazing relationships in Thalassia

beds, see García Rios (1990).

Views of Thalassia testudum Konig (turtle grass) in a shallow

water habitat.

G. Miller
Guide To The Ecological Systems Of Puerto Rico

223

Box 25. continued

The large, flat, strap-shaped leaves of turtle grass provide important vertical structural habitat for many small epiphytic plants and animals. Turtle grass

and other seagrasses, with their associated flora and fauna, create a complex

epibenthic community distinct from other marine habitats in the sublittoral

zone.

Thalassia anatomically lacks well-developed support tissue, so can bend

with the currents and wave action. The large leaves create drag on the water,

reducing its velocity, reducing erosion, and allowing for organic particulates 

to settle in place, important to the detrital-based component of the food chain.

Growth is optimal in gentle, clear lagoons in depths from 0.5 up to 30 meters

(2 to 90 feet). Turtle grass can tolerate salinities ranging from 10 to 48‰, with

normal sea water as the optimal (33‰) salinity. Leaves grow in clusters from

nodes and are sheathed at the base. When excavated, the rhizome is hairy, and

fibrous adventious roots are evident. The rhizomes are creeping and generally

located 5 to 10 centimeters (2 to 4 inches) into the substrate.

They are easily removed by hand and require a gentle wash in order to see

the various rhizome and root structures. If you slit the rhizome, it is possible to

observe the aerenchyma tissue with the large lacunae. This porous tissue, with

its large air spaces, promotes the movement of oxygen into the rhizome and

fine roots. Frequently, the rhizome and roots grow in substrates with little to

no oxygen available.

What conditions in the environment produce changes in turtle grass?

Nutrient enrichment via human sources or seabird excrement can cause a shift

to Halodule wrightii Ascherson (shoal grass). It is thought that shoal grass has

an advantage in that it can grow vertically more rapidly. Infections can reduce

or eliminate turtle grass. Higher water temperatures, altered salinity, and

increased sedimentation can cause a decline in turtle grass. Algae blooms can

block light and increase turbidity. As turtle grass dies out, bottom sediments

are more easily disturbed by wave action, boats, and so forth, thus expanding

the decline of turtle grass. In general, areas with frequent disturbance are likely to have a multispecies community. When the benthic environment is stable,

usually a monospecific community such as turtle grass will be found.

For more information on this species, see den Hartog 1970, Hemminga

and Duarte 2000, Howard 1979, and Littler et al. 1989.
General Technical Report IITF-35

224

Box 26. Syringodium filiforme Kuetzing (manatee grass)

All genera of seagrasses have fairly 

thin, blade-like, flat leaves, except

Syringodium filiforme Kutzing (manatee grass). It has cylindrical leaves. It 

is frequently found growing mixed with

turtle grass, but it can grow in a monospecific population. Manatee grass 

occurs in tropical waters of the western

Atlantic Ocean, Gulf of Mexico, and 

the Caribbean Sea. It typically grows in 

water 10 meters or less (33 feet), but in

extremely clear water it has been found 

at depths of 20 meters (66 feet). The

cylindrical, stiff, light green leaf blades

differ in length from 2 to 30 centimeters

(1 to 12 inches) and in width from 1 to 2

millimeters (less than z inch). The rhizome of manatee grass is 2 to 4 millimeters (around z inch) in diameter and it serves as the primary food storage

organ. It produces two to four roots with root hairs, scale leaves, and short

shoots at each node. The small shoots then give off two or three thread-like

(filiform) leaves, which are terete (round).

The plants are dioecious. Flowering is controlled by water temperature,

with 25 °C (77 °F) being the critical temperature in the waters of Puerto Rico

and the Virgin Islands. Flowers form on inconspicuous raceme inflorescences.

Fruits are small, ovoid, beaked, and about 6 millimeters (4-inchs) long.

Manatee grass is thought to be intermediate in the succession sequence in

seagrass communities in the Caribbean. Nutrient supply may be critical, with

macrobenthic algae initially occupying open sediments, such as blowouts or

areas opened by hurricane scouring. Manatee grass then invades, followed by

turtle grass. Turtle grass, through interference competition for light and nutrients, replaces manatee grass. Turtle grass populations will then control that site

until the next physical disturbance or pollution event creates a gap that manatee grass can invade.

For more information on this species, see Dawes 1998, Howard 1979, and

Kaplan 1988.

Syringodium filiforme Kutzing (manatee

grass) growth form.

G. Miller
Guide To The Ecological Systems Of Puerto Rico

225

Ta

ble

2

3

—

N

a

m

e

s

a

n

d

c

h

ara

cteristic

s

of th

e

s

e

a

gra

s

s

e

s

of P

u

erto

Ric

o

Com

mon

S

pecies name Family

Habitat Distinguishing features

Thalassia testudinum

Turtle H

y

drocharitaceae 0.5 to 20 meters (2 to 65 feet) Lon

g, flat, strap-shaped leaves up to

Konig

grass deep, mostly in

depths < 10 1 meter (3 feet) lon

g

with 9 to 15

meters (33 feet); san

d

y

bottoms; parallel veins, rou

n

ded apex; older

low

disturbance climax species; leaves usually covered in epip

h

ytes;

east an

d south

west coast; creates an ap

pearance of a vast

com

mon

green

meadow

Halophila decipiens Sea vine or H

y

drocharitaceae 0.5 to 30 meters (2 to 100 feet) Slen

der vine-like stems; leaves

Ostenfeld

d

warf deep; q

uiet lagoons an

d

brackish op

posite at the nodes, leaves oval an

d

seagrass pon

ds; can tolerate turbid

min

utely toothed; one prominent

polluted

water; soft bottoms; mid

vein

per leaf; grows as small

com

mon

patches up to 3 feet (1 meter) across

Halophila baillonis Midrib

H

y

drocharitaceae Shallow

water; 1 to 3 meters (3 Delicate, with thin rhizomes, leaves

Ascherson seagrass to 10 feet) deep; san

d

y or m

u

d

d

y in two or four pairs at shoot apex

bottoms; small distrib

ution in formin

g a pseu

do w

horl, blades

P

uerto Rico oblon

g to elliptic, apex obtuse, blade

margin

with fine hairs

Halophila engelmannii Six-leaved

H

y

drocharitaceae Shallow

water; 1 to 3 meters (3 Resem

bles the alga Caulerpa

Ascherson seagrass to 10 feet) deep; q

uiet lagoons, paspaloides; leaves smooth, flat with

pon

ds or boat harbors; soft distinctive midrib an

d

veins; stalks

bottoms of san

d or m

u

d; erect in

water; leaves in

w

horls of six

restricted

distrib

ution to eig

ht at top, up to 20 centimeters

(8 inches) lon

g; margins fine toothed

Syringodium

filiforme Manatee C

y

modoceaceae Shallow clear water; 1 to 20 Leaves cylin

drical (terete); forms

Kutzin

g

grass meters (3 to 65 feet) deep; fine dense mats; leaves up to 45

m

u

ds or san

d

y

bottoms; east an

d centimeters (18 inches) lon

g; may

south

west coast; com

mon

grow

with turtle grass

Halodule wrightii Shoal grass Zosteraceae Shallow

waters; 1 to 10 meters Leaves very

narrow

with flat blades,

Ascherson (3 to 33 feet) deep; fine m

u

ds to 4 to 10 centimeters (1.5 to 4 inches)

san

d

y

bottoms; colonizer after lon

g; leaf blade apex is top

ped

b

y

disturbance like h

urricanes; three teeth, with the mid tooth lon

ger;

com

mon forms extensive meadows

Ruppia maritima L. Wid

geon

Rup

piaceae Shallow

water of estuaries, Leaves narrow an

d lanceolate shaped,

grass lagoons, rivers, an

d fresh

water alternate arran

gement, apex

pointed,

lakes an

d

pon

ds, wide salt fine structure throu

g

hout bod

y

tolerance; mostly

brackish in

P

uerto Rico
General Technical Report IITF-35

226

Ostenfeld and Halodule wrightii Ascherson (shoal grass) are also very common on

the Atlantic and Caribbean shelves of Puerto Rico. Figure 65 illustrates the morphology of five of the species found in Puerto Rican waters.

Seagrasses and their associated macrobenthic algae are the basis for an

extremely productive ecosystem. It provides animals with a wide variety of plants

(macrobenthic and microepiphytic) to feed upon and space in which to live, hide,

and reproduce. There are five groups of organisms associated with seagrass communities of Puerto Rico (modified from García Ríos 1990). These include:

➢ Sessile algae and animals such as diatoms and a variety of invertebrates

➢ Microfauna such as protozoans, flagellates, and various small 

invertebrates

➢ Animals that travel or crawl on the bottom of seagrass beds such as 

snails, small crustaceans, and echinoderms

Figure 65—Morphology of five of the seagrass species found in Puerto Rican waters.
Guide To The Ecological Systems Of Puerto Rico

227

➢ Animals that swim and settle on leaf blades such as shrimp, copepods, 

and small jellyfish

➢ Animals that swim among leaf blades such as a variety of fish species,

especially larval and juvenile stages

Many animals present in these waters are valuable commercial species, such as

fish, conch, and shellfish. Seagrass beds are also in proximity to two other ecologically critical and commercially valuable ecosystems: mangrove swamps and coral

reefs (fig. 66). These also exhibit some of the same attributes of food chain and

space values as cited for seagrass beds. Together these three proximal key coastal

marine habitats are the heart and soul of the tropical nursery and feeding grounds

for most of Puerto Rico’s insular shelf. This is especially true of about 80 percent

of the fish of commercial value that are fished from these waters. These unique

underwater meadows are also critically important to endangered animals such as

Chelonia mydas (green sea turtle) and Trichechus manatus (West Indian manatee).

Both are known to graze these habitats heavily.

Most seagrass populations are well adapted for cloning, and by excavating their

underground parts, this strategy can be effectively observed. See fig. 67 for the

general morphology of seagrass. Some of these clonal populations are thought to be

thousands of years old. Could they be considered a form of old growth?

Remember that all marine SAV’s are adapted to the following conditions:

➢ They are able to grow submerged.

➢ They are totally tolerant to saltwater.

➢ They show a well-developed anchorage system to cope with waves 

or tides.

➢ They can successfully reproduce underwater—both sexually and 

asexually.

➢ They are tolerant to cropping by herbivores.

➢ They compete in a stressful environment.

➢ They can absorb essential carbon dioxide, phosphates, and NO4 via 

the leaf epidermis without the presence of stomata or through roots.

An interesting field exercise is to conduct a survey of macrobenthic algae 

encountered in SAV communities and how the algae differ from the flowering

plants. In addition, seagrass beds have many animals associated with them. These,

too, can be surveyed and discussed in terms of their life cycle stages, numbers, and

position in the ecosystem, and so forth. The following list includes some of the
General Technical Report IITF-35

228

Figure 66—Typical partitioning of subsystems in a tropical coastal area. The mangroves and seagrasses retain the flows of nutrients from the land, ensuring clear water

for the corals, which in turn constitutes a means of protection to counter erosion of the coast.
many macrobenthic marine algae and animals likely to be encountered in seagrass

beds of Puerto Rico.

Macrobenthic Algae Animals

Green Fish (short list)

➢ Acetabularia crenulata ➢ Sparisoma radians

Lamouroux (white mermaid’s (parrot fish)

wineglass) ➢ Acanthurus chirurgus (surgeon fish)

➢ Avrainvillea longicaulis ➢ Sphyraena barracuda (barracuda)

(Kuetzing) Murray & Boodle ➢ Megalops atlanticus (tarpin)

(paddle-blade alga) ➢ Ablennes hians (needle fish)

➢ Avrainvillea nigricans Decaisne ➢ Silversides, herring, anchovies 

(soft fan alga) (small silver-colored fish that 

➢ Bryopsis pennata (Harvey) form massive schools in calm

Collins & Hervey (sea fern) waters of seagrass beds and 

➢ Caulerpa mexicana Kuetzing mangrove channels)

(yellow leaf alga)

Guide To The Ecological Systems Of Puerto Rico

229

Figure 67—General features of the morphology of a seagrass.
General Technical Report IITF-35

230

➢ Caulerpa racemosa (Forsskal) ➢ Sphaeroides spengleri (banded 

J. Agardh (grape alga) puffer)

➢ Caulerpa sertularioides Boergesen (green feather alga)

➢ Cladophoropsis spp. (turf alga) ➢ Holocentrus rufus (squirrel fish)

➢ Codium decorticatum ➢ Thalassoma bifasciatum (bluehead 

(Woodward) Howe (dead wrasse)

man’s fingers) ➢ Hemiramphus brasiliensis (bally-

➢ Dictyosphaeria cavernosa hoo)

(Forsskal) Boer. (green ➢ Hippocampus reidi (seahorse)

bubble alga) ➢ Aetobatus narinari (spotted eagle 

➢ Enteromorpha spp. (green ray)

tube alga) ➢ Synodus spp. (lizard fish)

➢ Halimeda incrassata (Ellis) ➢ Epinephelus guttatus (red hind 

Lamouroux (three finger seabass)

leaf alga) ➢ Dasyatis americana (southern 

➢ Halimeda opuntia (L.) stingray).

Lamouroux (coralline Reptiles

watercress alga) ➢ Chelonia mydas (green sea turtle)

➢ Halimeda tuna (Ellis & Mammals

Solander) Lamouroux ➢ Trichechus manatus (West Indian 

(stalked lettuce alga) manatee)

➢ Penicillus capitatus Lamarck) Invertebrates

(shaving brush alga) (Herbivorous predators)

➢ Udotea conglutinata ➢ Diadema antillarum (long-spined 

Lamouroux (mermaid’s fan) sea urchin)

➢ Udotea flabellum (Ellis & ➢ Lytechinus variegatus (green sea 

Solander) Lamouroux (hard urchin)

fan alga) ➢ Tripneustes ventricosus (West 

➢ Valonia ventricosa J. Agardh Indian sea egg)

(sea pearls) ➢ Echinometra lucunter (red rock 

➢ Vaucheria sp. (vaucheria) urchin)

Brown (Nonherbivorous)

➢ Dictyopteris spp. (brown strap ➢Bartholomea sp. (sea anemone)

alga) ➢ Aplysia dactylomela (sea hare)

➢ Dictyota divaricata Lamouroux ➢ Amphipods

(strap alga)
➢ Padina sanctae-crucis ➢ Cassiopeia frondosa (upside-down

Boergesen (tan petticoat alga) jellyfish)

➢ Sargassum natans (L.) Gaillon ➢ Gastropod snails

(sargassum seaweed) ➢ Strombus gigas (green conch)

Red ➢ Strombus pugilis (fighting conch)

➢ Acanthophora spicifera (Vahl) ➢ Cassis tuberosa (helmet conch)

Boergesen (red brittle alga) ➢ Isopods

➢ Ceramium sp. (red banded ➢ Ludwigothuria mexicana 

alga) (sea cucumber)

➢ Chondria sp. (red tuft alga) ➢ Nudibranchs

➢ Dictyurus occidentalis ➢ Octopus briareus (reef octopus)

J. Agardh (red lace alga) ➢ Oreaster reticulatus (West Indian

➢ Gracilaria spp. (red branched starfish) 

alga) ➢ Sabellastarte magnifica (magnifi-

➢ Polysiphonia sp. (polysiphonia) cent feather duster worm)

➢ Spyridia filamentosa (Wulfen) ➢ Shrimp (eight species are common)

Harvey ➢ Sepioteuthis sepioidea (reef squid)

Coral ➢ Various crabs

➢ Acropora cervicornis ➢ Stoichactis helianthus (Sun 

(staghorn coral) anemones)

➢ Millepora complanata ➢ Panulirus argus (spiny lobster)

(flat-topped fire coral) ➢ Ophiocoma echinata (spiny brittle 

➢ Porites spp. (finger corals) star)

➢ Siderastrea radians (shallow- ➢ Pinna carnea (amber pen shell)

water starlet coral) ➢ Modulus modulus (Atlantic 

➢ Manicina areolata (rose coral) modulus)

➢ Oculina diffusa (ivory bush ➢ Codakia orbicularis (tiger lucine 

coral) clam)

➢ Agaricia agaricites (lettuce- ➢ Hermodice carunculata (fire worm)

leaf coral) ➢ Haliclona rubens (breadcrumb 

sponge)

As is the case for so many important natural ecosystems, seagrass beds are in a 

state of decline or disappearing in many areas of the world where an estimated 100

000 hectares (247,000 acres) have been lost. The rate of loss is poorly documented.

However, in one of the most carefully documented cases—the Chesapeake Bay 

of the Eastern United States—less than 10 percent of the original seagrass beds

remain. A similar dieoff of turtle grass occurred in Florida Bay in the 1980s. Puerto

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Rico is no exception. To maintain the vital functions of these communities, it is

essential that they be understood, appreciated, and protected. The coastal zones

throughout the globe are undergoing the greatest increases in human population,

and this is where seagrasses occur. Many anthropogenic activities will continue to

degrade and accelerate the loss of seagrass beds. Following is a list of some of the

important stressors that can cause the decline or extirpation of seagrass beds.

Stressors are known to both reduce species diversity and cause species shifts

(Hemminga and Duarte 2000). All of these are ongoing in the Caribbean, and most

are affecting Puerto Rico’s seagrass populations.

Anthropogenic stressors:

➢ Dredge/fill operations

➢ Industrial effluent (organic and inorganic)

➢ Municipal effluent

➢ Oil spills

➢ Agricultural nutrient enrichment (especially nitrates and phosphates)

➢ Sedimentation from construction and agriculture

➢ Motor boat props and wave scouring

➢ Harbor and marine development

➢ Commercial fishing techniques that disrupt the benthic zone

➢ Treasure hunting (use of sucker dredges and drag lines)

➢ Extirpation of large vertebrate grazers, such as sea turtles and manatees

➢ Power plants (temperature change)

➢ Effects associated with El Niño and global climate change

➢ Commercial cropping of seagrasses for aquaculture

➢ Recreation trampling and anchor scarring

➢ Introduced alien species

Natural stressors:

➢ Storm scouring (especially hurricanes)

➢ Excessive grazing by herbivorous predators

➢ Algae blooms

➢ Seasonal temperature changes

➢ Salinity change associated with storms

➢ Diseases, such as the slime-mold-induced wasting disease

➢ Excessive sedimentation from terrestrial erosion

The seagrass ecosystem constitutes a vital wetland in the marine waters of the 

United States, and more can be done to protect it. 
For further reading see Austin 1971, Ballantine 1971 and 1977, Cowardin et al.

1979, Dawes 1998, Delgado González 1978, den Hartog 1970, González Liboy

1979, Harlin 1975, Jackson et al. 2001, Kikuchi and Peres 1977, Kjerfve 1998,

Littler et al. 1989, McRoy and Helfferich 1977, Ogden 1980, Phillips and McRoy

1980, Scientific Committee on Problems of the Environment 1997, Thayer et al.

1975 and 1984, Vicente 1992, and Zieman 1976.

Coral Reefs

For many people, the term “coral reef” immediately conjures up images of crystal 

clear water filled with vast schools of beautifully colored fish, swimming over and

within an underwater seascape filled with an array of colorful corals. This perception is only partially accurate. In fact, the coral reef and its inhabitants form a complex ecosystem filled with aggressive behavior, heavy predation, complex symbiotic relationships, and very specific species zonations. In addition, many organisms

are nocturnal feeders and may rarely be seen. Coral reefs are frequently characterized as the species habitat equivalent of tropical rain forests, that is, the sea’s most

structurally complex and taxonomically diverse ecosystem. Estimates of coral reef

species range from 600,000 to more than 9 million species worldwide (Knowlton

2001). Coral reef development is generally limited by water quality and temperature (fig. 68).

So, what is coral? Coral is the common name for a variety of invertebrate

marine organisms that belong to the phylum Cnidaria (coelenterata). There are an

estimated 9,000 species of cnidarians in three classes.

➢ Hydrozoa–hydras, Portuguese man-of-war, fire corals (3,000 species)

➢ Scyphozoa–jellyfish (200 species)

➢ Anthozoa–hard corals, sea anemones, sea whips, sea fans, sea pens 

(6,000 species)

The following list will help you understand the features of this animal group.

➢ They have external or internal skeletons.

➢ They exhibit stony, horny, or leathery consistency.

➢ The term coral is particularly applied to the stone-like hard corals, such 

as Acropora (order Scleractinia), of which there are over 1,400 species, 

and the horny corals such as Gorgonia, of which there are an estimated

1,200 species.

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Figure 68—Global distribution of coral reefs (dark hatching), along with the major patterns of surface currents. Reef growth is generally limited by water temperature down to 18o or 20o C (the light shaded area is the 20o C isotherm band). Reefs are predominantly distributed on the eastern margins of continents where favorable currents (emphasized by thicker arrows), of clean low nutrient water are present.
Guide To The Ecological Systems Of Puerto Rico

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➢ Most corals are named for their individual appearances:

➢ Elkhorn ➢ Star ➢ Fan

➢ Staghorn ➢ Mushroom ➢ Whip

➢ Brain ➢ Finger ➢ Rod

➢ All cnidarians produce cnidocytes (stinging cells).

➢ Food capture is by the use of stinging cells for predation of zooplankton.

➢ They have primitive body organization surrounding a large hollow, 

central gut (coelenteron).

➢ Most corals are tropical and found in shallow marine waters.

➢ Reef-building corals are restricted to clear, warm water, generally less 

than 90 meters (295 feet) deep.

➢ They have a polymorphic life cycle (more than one phase).

➢ There are two body types:

➢ Medussae–free swimming.

➢ Polyps–sedentary with tentacles (fig. 69).

➢ Life expectancy varies from one season (hydra), to 90 years (sea

anemones).

➢ Most have the ability to regenerate new body parts from damaged 

individuals.

➢ Many possess single-celled endosymbiotic algae in their tissues 

(section on symbiosis follows).

➢ Body plan is simple consisting of three layers:

➢ Ectoderm–protection

➢ Endoderm–digestive layer

➢ Central mouth surrounded by tentacles for food capture

➢ No brains or heads

➢ No organs formed, complexity is not beyond tissue level (fig. 70).

Corals are tiny animals that form vast colonies that attach to firm surfaces on 

the ocean bottom. The living reef is built upon vast layers of old calcium carbonate

laid down by innumerable earlier generations. The living part of the reef is its outer

layer. The individual animals are referred to as polyps. The polyps are able to 

generate calcium carbonate, which they use to build protective skeletal structures 

in many sizes and shapes. Some corals (hermatypic reef building) build complex

skeletal structures that form the massive limestone deposits we call the coral reef.

A large reef is actually composed of countless numbers of coral animals and literally tens of thousands of invertebrates and fishes. Also mixed into the reef are a

vast number and coverage of algae. Not all cnidarians are reef builders. Many, in
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fact, live singly and remain unattached, such as jellyfish and the Portuguese manof-war. Many organisms on a reef are potentially hazardous to unprotected skin,

especially these latter groups (Halstead 1967, Halstead et al. 1990). Many species

can sting, bite, shock, puncture, and cause abrasions.

Various factors affect the growth and development of reef building (hermatypic) corals. The following list describes the narrow range of conditions that must

be met in order for these corals to exist.

➢ Shallow water with waves and currents

➢ Firm substrates for polyp attachment

➢ Undiluted sea water (33 to 35‰ sodium chloride)

➢ High amounts of light

➢ Zooxanthellic symbiotic algae 

➢ Water temperatures of 18 to 25 oC (64 to 78 oF)

➢ Low-turbidity, high-clarity water

➢ Waters with good circulation to provide high oxygen levels, remove

wastes, and bring in food organisms

Oceanic reefs are autotrophic units operating at a high level of productivity, 

with fast turnover rates, short life cycles, and high efficiency in using and recycling

Figure 69—Cross section through a hard coral polyp.
nutrients. Vast amounts of endosymbiotic algae are present within the coral polyps.

In addition, large quantities of other phytoplankton, macrobenthic attached algae,

and submerged seagrasses may be present. All give off metabolites into the water

column. As a result, the water circulating within the reef system has much higher

amounts of organic detritus, dissolved nutrients, and concentrations of zooplankton

than does the surrounding open ocean. Thus, the water surrounding the corals is

nutrient enriched. These nutrients can be picked up by the microvilli covering the

polyp’s epithelium. As a result of these factors, coral reefs exhibit high productivity

ranking them one of the Earth’s highest producing ecosystems (fig. 71). Although

coral reefs cover less than 0.1 percent of the area of the world’s seas, they are

home to nearly one third of all marine fishes.

Coral reefs are a seeming paradox in that they are highly productive ecosystems, or islands of productivity, frequently surrounded by large areas of inherently

low natural productivity. This was brought to light recently in the case of Puerto

Rico in a satellite view of the equatorial and north Atlantic Ocean on the cover of

Science (2001). It showed that the islands of the West Indies are in large part surrounded by very low productivity ocean water. To the east of Puerto Rico, for over

1667 kilometers (1,000 miles), lie the least productive waters in the north Atlantic

Ocean (fig. 72). In spite of this seeming biological desert to the east, Puerto Rico’s

shelf waters are quite productive thanks in large part to coral reefs, seagrass beds,

Guide To The Ecological Systems Of Puerto Rico

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Figure 70—Body forms of Cnidaria.
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Figure 71—

Comparative productivity of ecosystems.
Guide To The Ecological Systems Of Puerto Rico

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and mangrove swamps (fig. 73). Therefore, from an ecological standpoint, the primary resource values of a reef are its high productivity, variable habitat, and high

species diversity. Up to 180 species of edible fish are found on the reefs of Puerto

Rico. The reefs contain an enormous amount of marine protein in a relatively localized area thanks to concentrations of nutrients and microhabitats for growth, and

reproduction by a large variety of noncoralline animals.

When scuba diving, snorkeling, or looking through glass-bottomed boats, 

people are immediately struck by the zonation they view within the reefs. One of

the first researchers to describe this phenomenon was Charles Darwin. In fact, the

terms coined by Darwin in 1842 to describe the types of reefs are still used today.

The main types of reefs are:

➢ Barrier reefs occur along continents such as Australia’s Great Barrier 

Reef, which is 1935 kilometers (1,200 miles) long. This massive reef 

is separated from the mainland by large lagoons and channels (fig. 74).

➢ Fringing reefs occur around islands and are adjacent to continents. In 

some cases they are shoreline projections.

➢ Atolls are horseshoe-shaped ridges of reefs and islands, with a lagoon 

in the center and often are old sunken volcanic cones. They are typical 

of the Pacific and Indian Oceans, and generally not associated with 

continents.

Figure 72—Puerto Rico and adjacent waters. 

G. Miller
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Figure 73—A diagrammatic representation of the different types of new coral reefs built on top of old previous reefs, over the underlying base rock,

including volcanic rock and sediments. The major influences are marked as arrows indicating the direction of that influence.
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Figure 74—Schematic representation of interaction between the principal coastal marine ecosystems of the Caribbean.
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➢ Bank reefs are open sea reefs without a central lagoon and generally 

surrounded by deep water, for example, the Great Bahama Bank.

➢ Patch reefs are generally small irregular-shaped reefs or accumulations 

of coral separated by a sandy bottom. They are frequently located to 

the rear of fringing reefs and may appear as coral mounds in seagrass 

beds.

Barrier reefs and atolls are not found in the waters of Puerto Rico, but are 

found off the coast of Belize in the western Caribbean. No matter what type of reef

is being visited or studied, the organisms found will exhibit specific zonation patterns, that is, each species tends to show up in a particular area on a reef based on

its needs and tolerances for the conditions controlling growth and development in

these zones, such as wave action, light, salinity, depth, and sediment (fig. 75). The

zones typically found on a reef are:

➢ Lagoon. A shallow, protected, calm, clear water area behind a barrier

or fringing reef. It generally has large sand flats, seagrass beds, and 

dispersed coral groups.

➢ Rear zone. An area behind a fringing reef, usually protected where the

water is calm. It may contain patch reefs, various shallow water corals, 

and seagrass beds.

➢ Reef flat (crest). The top of the reef. It can be subject to exposure. 

Many dead and fragmented hard corals are present.

➢ Breaker zone (fore reef). An area on the seaward side projecting toward

deeper water, likely to have elkhorn corals.

➢ Buttress zone. A mixed coral zone in deeper water.

➢ Terrace. An area of mixed staghorn, star coral, and other large mound

corals.

➢ Slope zone. An area of increasing water depth on the seaward side, 

gradual depletion of some coral owing to reduced light.

➢ Deep forereef (reef wall). Underwater cliffs that may drop at angles 

nearing 90o. This may signify the edge of an island’s or continent’s 

underwater shelf.

According to Jackson (1991), the total number of coral species recorded from 

different reefs decreases with depth, the number of species is greatest at intermediate depths and highest cover, and lowest diversity occurs at the shallowest depths

where disturbance is greatest.

The upper limit of most reef crests is set by the level of low tides because dry

polyps will die in a short period. Often this area contains macrobenthic algae, as
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Figure 75—

Generalized zonation of Caribbean reefs.
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they are more tolerant to desiccation along the ridges and crest of this shallow area.

Algae can cover more than 50 percent of the total area of many reefs. The algae

form the bottom of the food chain for grazers, including many fish. There are certain groups of red and green algae particularly important to reef formation. Red

coralline algae, like Lithothamnion, can be found encrusting on reef tops and wave

breaking ridges. They grow rapidly and trap loose sand and shell fragments,

cementing them to the solid reef underneath. The common green alga genus,

Halimeda, which looks somewhat like an underwater cactus, is also calcified and

has a segmented branching pattern. Halimeda spp. are some of the most common

organisms on the reef. They are found in deep waters of reef slopes, reef passages,

on coral in upper zones, and occur in carpets on the bottom of lagoons. Halimeda

contributes both calcium carbonate and biomass to the reef. They are the source of

much food for herbivores and the white coralline sediments that are produced when

they die and degrade. Up to 25 percent of the limestone on a reef may be the product of Halimeda growth.

There are considerable differences in the coral fauna and general animal

species composition found in reefs of the Caribbean compared to the Pacific Ocean

region. There are few species of corals, mollusks, echinoderms, and fish common

to both regions. Coral reefs of the western Pacific and Indian Oceans are comparatively richer in coral than those of the Caribbean. The Pacific has 100 genera compared to 26 in the Caribbean (75 percent more) and 700 species of coral compared

to 90 in the Caribbean (85 percent more). Almy and Carrión (1963) found 38

species of shallow water stony corals in Puerto Rico’s waters. On the other hand,

when you look at the presence of the soft coral group (class Anthozoa, subclass

Alcyonaria), the Caribbean Sea shows the highest abundance and diversity of

Gorgonians (sea fans, sea whips) in tropical waters.

Coral reefs, with their diverse plant and animal species, are beneficial to natural processes and human society. The following list identifies some of these benefits and ecological services.

➢ Food for both reef and open water food chains, as well as the human 

food chain

➢ Living space for vast numbers of aquatic plants and animals, and on 

large coral islands for large numbers of tropical terrestrial plants and 

animals, and humans

➢ Coastal protection during storms

➢ Help to control sediments in coastal waters, and reduce coastal erosion
➢ Source of beach sands

➢ Importance for coastal nutrient cycles

➢ Marine carbon budget (atmospheric carbon dioxide extraction)

➢ Importance for local folk medicines and pharmaceutical research in 

anticoagulants, antimicrobials, anticancer properties, and mechanisms 

of drug action

➢ Construction materials for roads, walls, buildings, ports, and airport 

runways

➢ Recreation

➢ Ecotourism

➢ Ecological research

➢ Aesthetics (fantastic array of colors and forms)

Coral reefs provide an estimated $400 billion to fishing and tourism industries 

around the world (Normile 2000a, 2000b, 2000c). Unfortunately, today coral reefs

and their many species are experiencing rapid changes in various aspects of water

quality and species composition, which can only be viewed as negative. The health

of most reefs is largely dependent upon what goes on in nearby adjacent continental or insular land masses. In addition, there are numerous diseases currently affecting many corals, and an increasing number of reefs and species are experiencing

severe episodes of dieback (see coral dieback section that follows). It is estimated

that as much as 90 percent of all coral reefs examined are negatively impacted, and

ironically, up to 90 percent of the species on the coral reefs of the world remain

poorly or largely undescribed. In addition, there are many potential and real threats

to the very existence of reefs. Most of the reefs experiencing severe degradation are

located in areas near human population centers or terrestrial areas being degraded

by anthropogenic activities, such as large-scale agriculture. Nearly 27 percent of

the world’s coral reefs are considered at high risk, and up to 10 percent of the reefs

have been declared dead. Southeast Asia’s coral reefs contain the largest number of

species and yet are the most threatened of any region (Raven and Berg 2001).

Coral reefs cannot be viewed as isolated ecosystems. They are part of an interactive

complex of ecosystems that can involve massive land and sea areas. They are

linked to seagrass beds and mangrove swamps on the coastal fringe. In addition,

alterations in terrestrial landscapes hundreds to thousands of miles away may

threaten their productivity and general health. For a detailed review of the state of

coral reefs in the Caribbean, see Goenaga (1989). The following list identifies

some of the common threats to reefs. The majority affect coral reefs in the

Caribbean and Puerto Rico.

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➢ Vessel groundings and sinkings

➢ Anchor damage

➢ Oil spills

➢ Hazardous wastes

➢ Solid wastes

➢ Sewage wastes

➢ Siltation from deforestation (inland removal of upland forests and 

coastal mangroves)

➢ Beach nourishment activities for recreation beaches

➢ Dredging and filling

➢ Fishing-lines, traps, nets; overfishing

➢ Use of chemicals and explosives in fishing

➢ Tropical fish collections for aquarium trade

➢ Invertebrate collections for study and display

➢ Diving and snorkeling damage

➢ Tropical storms, especially hurricanes/typhoons

➢ Oxygen depletion

➢ Loss of predatory algae grazers

➢ Temperature changes (powerplant and industrial thermal effluents, 

and global warming)

➢ Ozone loss–increased ultraviolet radiation exposure

➢ Disease outbreaks (Diadema virus/bacterium and coral bleaching)

➢ Nutrient eutrophication

➢ Mass collections for sale as tourism trinkets and jewelry (U.S. 

imports 730 tons per year, world’s largest importer) (fig. 76)

➢ Eruption of alien species (“crown of thorns”)

➢ Offshore drilling and release of muds

➢ Harbor construction

➢ Tourist facilities development

➢ Pesticides

➢ Coral mining for construction materials

➢ Upland mine discharges (sediment and chemicals)

➢ Military activities (explosions, shock waves, sedimentation, and 

weakening of corals that will be easily damaged by subsequent 

storms)

➢ Shell collecting 
There are roughly 453 000 square kilometers (177,000 square miles) of coral 

reef scattered throughout the world’s tropical and subtropical seas (United Nations

Environmental Programme 2001). Today, reef conservation is a high-profile international topic. About 50 percent of the countries with coral reefs have reserves in

place to safeguard some of them. In most cases they are underfunded and understaffed. As of March 2000, 20 percent of all U.S. reefs were proposed off-limits

and designated no-take zones by the U.S. Coral Reef Task Force. As a result,

President Clinton, just prior to leaving office in December 2000, announced the

creation of the Northwestern Hawaiian Islands Coral Reef Ecosystem Preserve

extending 1935 kilometers (1,200 miles) long and 161 kilometers (100 miles) wide.

This 35-million hectare (86.5-million-acre) preserve is the largest conservation area

created in U.S. history and the second largest marine-protected zone on earth, second only to the Great Barrier Reef in Australia. This new area protects 70 percent

of all U.S. coral reefs and an estimated 7,000 species of plants and animals. It will

prohibit most consumptive uses of the ecosystem in 5 percent of the reserve, which

will be set aside in 15 preservation areas. Other countries are also considering

adding more preserves to curtail the rapid depletion of fish stocks and many other

marine species associated with reefs. Without special protection, many of these

areas are facing extinction. Less than 1 percent of the world’s waters are protected

in marine preserves. For those areas that have received special protection, recovery

has shown to be quite rapid and biodiversity is conserved. In June 1998, President

Clinton also issued Executive Order 13089, which directed all U.S. federal 

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Figure 76—Shell shop showing the effects of mass collection of shelled animals for

sale to tourists. 

G. Miller
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agencies whose actions can affect U.S. coral reef ecosystems, to seek implementation of measures to reduce and mitigate degradation, and to restore damaged coral

reef ecosystems.

Keeping Your Keel off Coral

More than 1 million snorkelers and scuba divers visit coral reefs yearly, and this 

number is growing as popularity of the sport and interest in ecotourism increases.

Reefs are degraded by many people collecting specimens, anchoring boats, and

standing on corals or algae. The following is a description of coral reef restrictions

in place for protected waters in the U.S. Virgin Islands National Park. “No person

shall cut, carve, injure, mutilate, remove, displace, or break off any underwater

growth or coral formation. No digging in the bottom is permitted, and no rope,

wire, or other contrivance should be attached to any coral, rock, or other underwater formation. No watercraft shall be operated in a manner, nor shall anchors or

other mooring devices be cast or dragged so as to cause damage to any underwater

features of the reef” (Allen 1992). These are all destructive activities to be avoided

or minimized whenever possible.

For more information on reducing recreation impacts on coral reefs, contact

Friends of the Sanctuaries, Center for Environmental Education, 624 9th Street,

NW, Washington, DC (202) 737-3600 and see app. 4.

Puerto Rico’s coral reefs are found in many areas of the insular shelf but are

most concentrated in two areas: the southwest in the Cabo Rojo/La Parguera area

and the northeast from Fajardo to Culebra, Vieques, and the many small islets

going east toward the U.S. Virgin Islands (see app. 2). The two largest areas of the

insular shelf are west of Boquerón, where it extends for 22 kilometers (13 miles),

and east of Fajardo, where it extends all the way to St. Thomas, in the U.S. Virgin

Islands. The reef at the mouth of Boquerón Bay is not well developed. There are

numerous well-developed reefs in the eastern area around Vieques Sound. On the

northeast coast, the best reef development occurs on the string of fringing reefs that

run along a narrow 30-kilometer (18-mile) submarine ridge, which runs from the

northeastern tip of Puerto Rico to Culebra in an east-southeast direction. Corals 

are present in most of Puerto Rico’s marine waters, but these are the areas where

they are extensive and relatively easy to access. In many areas on the west and

north coasts, reefs have been killed or are absent owing to the higher number of

rivers that discharge large quantities of freshwater, sediments, and pollutants into

these marine waters. The north coast rivers carry greater loads of pollutants from

construction, various industries, sewerage plants, and urban runoff. Fortunately for

the north coast, there are still reefs present protecting the calm-water sandy beaches
found along Isla Verde, Piñones, and Luquillo. These extensive sandy beaches are

protected from higher energy waves of the Atlantic by near-shore fringing reefs.

Most reefs are degraded by sediments and runoff being released by the continued

urban development going on in the north coast area. Corals are very sensitive to

these materials as they increase turbidity or cover the corals, thus reducing their

access to light and reducing their productivity. If the hard, exposed substrate is 

sedimented over, coral larvae cannot establish themselves, and sediments or other

effluents may consume oxygen, causing a drop in the aerobic conditions needed for

their survival. 

We will now turn to the description of coral reefs found in the La Parguera

area. La Parguera is in the municipality of Lajas on the southwest coast. The 

insular shelf is fairly extensive there and exhibits a complex array of mangrove

swamps, seagrass beds, and coral reefs. This area of coastal Puerto Rico is dry and

warm throughout the year, and exhibits relatively low urban development. The

waters exhibit high clarity, have low wave energy, and in this area are relatively

low in nutrients (oligotrophic). All are necessary conditions for coral reef development. The positioning of the three important and productive coastal ecosystems,

that is, seagrass, mangrove, and coral ecosystems, made these waters quite productive historically. Unfortunately, many of the near-shore reefs today do not exhibit

the once abundant fish populations seen prior to the 1970s. Some of this can be

attributed to overfishing. Spiny lobsters are also rare except for juveniles, whereas

they used to be quite common. The same is true for octopus and large conchs (various species). The reefs are still present, but their health has declined because of

bleaching events that occurred in 1987 and 1990. García et al. (1998) indicated that

more than 60 species of corals have been affected in the La Parguera area. In addition, hurricanes and other tropical storms have produced considerable physical

damage to the reefs as a result of waves and currents associated with them.

Because of reduced yields, fishing pressure on these reefs has greatly declined in

recent years. Many fishermen are now employed in the tourist industry. Today, La

Parguera’s reefs are being used extensively for recreation. Many more Puerto

Ricans have motor and sailboats and use the waters off La Parguera for a variety of

water sports. The coral reefs, mangrove swamps, and seagrass communities are

also used for field trip sites by educational institutions and ecotourism companies.

Many of the activities just mentioned can have serious effects on these ecosystems

caused by boat propellers, walking, sitting/standing on corals, collecting samples,

spear fishing, pollution produced by gas-powered engines, improper solid waste

disposal, and sediment disturbance.

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The La Parguera area has the highest number of shallow-water stony coral

species of any reef complex in Puerto Rico. The 38 shallow-water stony coral

species identified for Puerto Rico by Almy and Carrión Torres (1963) are present

on the reefs at La Parguera. Most species are located on the east ends of the reefs

in open back reef waters. These areas are somewhat protected and yet turbulent

enough to provide water with adequate oxygen and salinity content to promote

growth of a variety of corals. Another 30 species of shallow-water Gorgonian 

octocorals have been reported by Yoshioka snd Yoshioka (1989). The insular shelf

in the La Parguera area is 8 to 13 kilometers (5 to 8 miles) wide. At the edge of the

shelf, water depth is around 21 meters (70 feet) deep. It then drops rapidly to 37

meters (120 feet) along the shelf wall and, at its outer edge, will be nearly 549

meters (1,800 feet) deep before dropping to the Caribbean abyss.

The shallow-water reefs at La Parguera are located in two arcs along the insular shelf and are frequently referred to as the “outer” and “inner” reefs. The outer

reef arc is about 3.3 kilometers (2 miles) from shore; the inner reefs are approximately 1.6 kilometers (1 mile) from shore. The reefs are elongated east to west,

which allows them to interface with waves coming from the southeast into the bay

in front of La Parguera. The reefs are generally small, with the largest being

Margarita, about 3.3 kilometers (2 miles) in length (fig. 77). Water depth between

the two reef arcs varies from 12 to 21 meters (40 to 70 feet) in depth. The lagoons

immediately to the rear of the reefs vary from 0.5 to 7.5 meters (1.6 to 25 feet)

deep.

The two reefs easiest to access are Enrique and Caracoles (not labeled on the

figure). They are about 1.6 kilometers (1 mile) directly out from the boat rental

docks at La Parguera. 

Organisms likely to be observed on coral reefs in the La Parguera area include

the following:

Shallow-water stony corals

Porites porites (finger coral, box 27)

Millepora complanata (stinging fire coral)

Millepora alcicornis (branching fire coral)

Acropora palmata (elkhorn coral, box 28)

Acropora prolifera (fused staghorn coral)

Acropora cervicornis (staghorn coral)

Isophyllia sinuosa (cactus coral)

Montastrea annularis (common star 

coral)
Siderastrea radians (round starlet coral)

Siderastrea siderea (starlet coral)

Diploria strigosa (brain coral, box 29)

Diploria labyrinthiformis (depressed 

brain coral)

Favia fragum (star coral)

Agaricia agarites (foliose coral)

Manicina areolata (common rose coral)

Soft corals

Gorgonia flabellum (Venus sea fan)

Gorgonia ventalina (common sea fan, 

box 30)

Plexaurella grisea (split pore sea whip)

Pseudoplexaura sp. (sea rods)

Pseudopterogorgia americana (ostrich 

plume)

Eunicea spp. (knobby candelabra coral)

Other common invertebrates

Condylactis gigantea (purple anemone)

Stoichactis helianthus (sun anemone)

Zoanthus sociatus (green colonial 

anemone)

Zoanthus ocellaris (eyeball anemone)

Panulirus argus (spiny Caribbean lobster)

Echinometra lucunter (common urchin)

Diadema antillarum (black spiny urchin)

Lytechinus variegatus (green sea urchin)

Tripneustes esculentus (white urchin)

Haliclona rubens (red sponge)

Chondrilla nucula (brown sponge)

Hermodice carunculata (fire worm)

Ophiothrix angulata (brittle star)

Eucidaris tribuloides (pencil urchin)

Clypeaster rosaceus (heart urchin)

Meoma ventricosa (large heart urchin)

Guide To The Ecological Systems Of Puerto Rico

251

Mellita lata (sand dollar)

Chiton tuberculatus (West Indian 

chiton)

Atrina seminuda (spiny pen shell)

Pinna carnea (amber pen shell)

Cyphoma gibbosum (flamingo-tongue 

snail)

Ophiocoma echinata (large hairy 

brittle star)

Sabellastarte magnifica (magnificent 

feather duster fan banded worm)

Sabella melanostigma (feather duster 

worm)

Mithrax sculptus (small green crab)

Microthele parvula (small sea 

cucumber)

Holothuria mexicana (donkey dung 

sea cucumber)

Octopus briareus (reef octopus)

Crangon formosus (snapping shrimp)

Stenopus hispidus (barber shrimp)

Gonodactylus oerstedii (green mantis 

shrimp)

Aplysia protea (sea hare)

åAurelia aurita (moon jelly)

Oreaster reticulatus (West India sea 

star)

Strombus gigas (queen conch)

Macrobenthic algae

Greens:

Halimeda opuntia (L.) Lamouroux 

(coralline watercress alga)

Halimeda incrassata (Ellis) Lamouroux 

(three finger leaf alga)

Caulerpa racemosa (Forsskal) J. Agardh 

(green grape alga)
General Technical Report IITF-35

252

Common fish

Acanthurus bahianus (surgeon fish)

Holocentrus spp. (squirrel fish)

Scarus vetula (queen parrot fish)

Scarus guacamaia (rainbow parrot fish)

Gobiosoma spp. (gobies)

Thalassoma bifasciatum (bluehead 

wrasse)

Haemulon flavolineatum (french grunt)

Haemulon sciurus (blue striped grunt)

Pomacanthus arcuatus (gray angelfish)

Holocanthus ciliaris (queen angelfish)

Balistes vetula (queen trigger fish)

Chaetodon straitus (banded butterfly 

fish)

Chaetodon capistratus (four-eyed 

butterfly fish)

Anisotremus virginicus (pork fish)

Acanthurus coeruleus (blue tang)

Sphyraena barracuda (barracuda)

Stegastes spp. (damsel fish)

Abudefduf saxatilis (sergeant major)

Gramma loreto (fairy basslet)

Synodus saurus (lizard fish)

Aulostomus maculatus (trumpet fish)

Diodon hystrix (porcupine fish)

Gymothorax funebris (green moray eel)

Diodon holocanthus (puffer fish)

Hypoplectrus spp. (hamlets)

Chaetodipterus faber (spade fish)

Blennies (various genera and species)

Caulerpa sertularioides (S.G. Gmelin) 

Howe (green feather alga)

Udotea flabellum (Ellis & Solander) 

Lamouroux (fan alga)

Dictyota divaricata Lamouroux 

(Y-branched alga)

Dictyosphaeria cavernosa (Forsskal) 

Boergesen (green bubble alga)

Penicillus capitatus Lamarck (shaving 

brush alga)

Ulva lactuca L. (lettuce leaf alga)

Valonia ventricosa J. Agardh (sea pearls 

alga)

Reds:

Wrangelia argus (Montagne) Montagne 

(pink bush alga)

Spyridia filamentosa (Wulfen) Harvey 

(red bush alga)

Acanthophora spicifera (Vahl) 

Boergesen (brittle-branch alga)

Ceramium nitens (C. Agardh) 

J. Agardh (rose tuft alga)

Amphiroa fragilissima (L.) Lamouroux

(fragile-branched coralline alga)

Lithothamnion sp. (coralline shelf alga)

Macrobenthic sea grasses

Thalassia testudinum Konig (turtle 

grass)

Syringodium filiforme Kuetzing 

(manatee grass)

Halodule beaudettei (den Hartog) 

den Hartog (shoal grass)
General Technical Report IITF-35

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Figure 77—Location map of La Parguera, Puerto Rico and its marine ecosystems.
Guide To The Ecological Systems Of Puerto Rico

254

Box 27. Porites spp. (finger corals) 

There are a variety of 

stony corals, members of 

the class Anthozoa, in the

shallow coastal waters of

Puerto Rico associated with

coral reefs. The species

which will be profiled in 

this section all belong to 

the order Scleractinia. The

Scleractinia corals are the

master builders of the coral

reef because they secrete a hard calcareous skeleton.

Porites and Acropora are the two most important genera of hard coral in

the world. Porites has an estimated 30 species in the Pacific region and three

in the Atlantic/Caribbean. Acropora has 150 species in the Pacific and three in

the Atlantic/Caribbean.

When visiting a reef in Puerto Rico, the most common species of coral

likely to be encountered are the finger corals, members of the genus Porites.

Finger corals are probably the most common species present in the shallow

zones of most reefs, lagoons, and nearby seagrass beds. They get their common name because their growth form resembles the fingers of the human

hand. Not all Porites species are finger-like, as in the case of P. astreoides,

which is a gibbose (swollen) mass.

Porites porites (thick finger coral)

This is the most common finger coral. This coral forms finger-like clumps of

hard coral that may be thick or open, and irregularly shaped. At times, their

growth is straight and thick, forming a pavement-like formation that can support the weight of a small adult. It grows in variable water depths from 1 to 

49 meters (3 to 160 feet). Branches may be up to 2.5 centimeters (1 inch) in

diameter and can approach 25 centimeters (10 inches) in length. Its branches

are larger than the other finger corals and tend to have swollen ends. You will

often see its gray clear polyps extended during the day giving it a fuzzy look.

Porites furcata (thin finger coral)

This finger coral typically forms dense vertical branching colonies. Branches

may be to 1 centimeter (one half inch) in diameter. The tips of the forked 

Porites spp. growing in a shallow water habitat. Notice sea

urchins.

G. Miller
Guide To The Ecological Systems Of Puerto Rico

255

Box 27. continued

branches are not swollen. Some populations of this species can be bright 

purple. This species frequently produces large areas of coverage in shallow 

flat areas between reef islands or the rear zones of a reef. Coverage can be

hectares (acres) in size, forming a pavement-like appearance. It is associated

with all reefs at La Parguera and can grow in nearby seagrass beds. Their

dense colonies form habitats for numerous invertebrates such as sea urchins

and brittlestars.

Porites astreoides (yellow porous coral)

This species of Porites is not finger-like in appearance. This hard coral grows

as an expanded mass or as an encrusting mass. It can achieve diameters of 60

centimeters (2 feet) and is common on most back-reef areas of fringing reefs

and on patch reefs. It also may be present in seagrass beds and sandy lagoons.

It gets its name because its color is sulfur-yellow.

When visiting a reef, hard corals can be a problem for swimmers and

snorkelers if they do not have protection for the exposed parts of their body.

Many corals have sharp surfaces and will cause skin abrasions. The members

of the genus Porites are of little threat because their branches are rounded and

general surface textures are not very abrasive. They can be handled easily,

although it is recommended that no corals be touched if possible.

For more information on these and other coral species, see Almy, Jr. and

Carrión Torres 1963, Humann 1996, and Kaplan 1982.

Box 28. Acropora spp. (horned corals) 

Two species of the genus Acropora are very common on the reefs of Puerto 

Rico. They are normally found on the front side of reefs, although they can

appear in lagoons. Their common name is due to the fact that their branched

growth forms resemble the horny racks of elk and deer.

Acropora palmata (elkhorn coral) 

This large branched coral is the most common coral on the windward side of

can also occur in back reef areas and lagoons. This species’ growth form exhibits a main stem or trunk, with outward extending flattened colonial branches.

The branches actually resemble the horny antlers of a moose rather than an

elk. The branches will be rough to the touch owing to protruding cups. When

alive it is rusty-brown. Many reefs in Puerto Rico have suffered significant 
General Technical Report IITF-35

256

Box 28. continued

decreases in this species’

populations as a result of

whiting disease and severe

hurricane damage. Some

reefs have been turned into

virtual coral graveyards as 

a result of storm damage.

This species is known to

recover rapidly if storm

damage or disease episodes

are not frequent. Regeneration occurs via renewed

growth of damaged colonies, dislocated fragments, or through new colonies

formed from larval sets. Recovery from natural disturbances may take

decades. Some human disturbances may prevent recovery owing to the continuation of the disturbance in excess of the coral’s tolerance for the stressor,

such as chemical pollution or heavy sedimentation.

Under optimal conditions, this species can grow 13 to 15 centimeters (5 to

6 inches) per year. It is one of the main corals in Puerto Rico’s fringing reefs

and can cover hectares (acres) of surface area. Some colonies may grow to 3.7

meters (12 feet) in length in optimal habitats.

Acropora cervicornis

(staghorn coral)

This species has a more branched growth form and the individual bran-ches 

do resemble the antlers of a stag deer. Its branches are very rough as a result

of the large number of protruding tubular cups, which point toward the branch

tip. The individual branches 

are brown to yellow-brown,

cylindrical, and can grow 

to 2.5 centimeters (1 inch)

in diameter. Branched

clumps can grow to 2.4

meters (8 feet) in diameter.

Under optimum conditions,

it can grow 13 to 15 

centimeters (5 to 6 inches)

Acrophora palmate (elkhorn coral) growing in the fore reef

zone.

G. Miller

Acrophora cervicornis (staghorn coral) growing in a lagoon.

G. Miller
Guide To The Ecological Systems Of Puerto Rico

257

Box 28. continued

per year. The branches remain distinct and do not fuse. It is not as common on

the windward side of the reef as is elkhorn, and it tends to grow in depths of 3

meters (10 feet) or more. It has been found in depths to 49 meters (160 feet)

and is frequently observed in back-reef and lagoon sections of the reef. Lugo

et al. (2000) indicate that the zonation and overall morphology of coral reefs

are strongly influenced by their exposure to waves and hurricanes. Moderate

wave energy favors vertical and rapid growth, while high energy waves favor

slow and compact growth. Acropora palmata (elkhorn coral) and Acropora

cervicornis (staghorn coral) are susceptible to breakage and overturn during

major storms owing to their branching morphology.

For more information on this species, see Almy, Jr. and Carrión Torres

1963, Humman 1996, and Kaplan 1982.

Box 29. Diploria spp. (brain corals)

Some of the most striking corals on the reef 

are those that strongly

resemble the outer surface of the human brain.

Colonies form contoured hemispherical

domes. Some individuals get to be quite 

large and can weigh 

half a ton or more.

Diploria labyrinthiformis (depressed or grooved brain coral) 

This coral can grow quite large, is hemispherically shaped, and is yellowbrown in color. From a distance this hard coral looks like a large round boulder. When examined closely, it exhibits a hill and valley structure to the alignment of the coral polyps. The outer hills may be up to 2 centimeters (one

fourth inch) wide with the valley’s depression narrower. This coral is common

in rear and side areas, which are protected and may be more than 1 meter 

(3 feet) in diameter. They are mostly in depths of 4.6 to 15 meters (15 to 50

Diploria labyrinthiformis (depressed brain coral) growing in

the fore reef zone

G. Miller
For more information on the animals found in the reefs at La Parguera, see

Matthews (1967) and Glynn (1964).

La Parguera is also a major scuba diving port. One of the diving hot spots in

the Caribbean is the “wall,” which is the transition shelf edge zone to the deeper

areas of the insular shelf. The wall is only 10 kilometers (6 miles) from the waterfront. To dive the insular wall requires access to a larger boat with the necessary

support facilities, and there are more than 20 dive services operating throughout.

The wall runs for approximately 22 miles east toward Ponce and rivals any wall

diving in the Caribbean for ease of access and viewing of species diversity. Clarity

can be in excess of 30 meters (100 feet). The wall has lots of rowpore sponges, star

coral, pillar coral, black coral, yellow crinoids, anemones, and deep water

Gorgonians. Water depth ranges from 18 meters (60 feet) to 37 meters (120 feet).

The popularity of the La Parguera area has produced a construction boom in

second vacation homes, small hotels, and restaurants in the last decade. This has

caused serious deforestation in the area around the village. La Parguera is not only

an active tourist destination for its daytime water recreation, but also for its night

life. The waterfront from dusk to 1:00 a.m. is heavily plied by tourists seeking boat

trips to the nearby phosphorescent bay, as well as the restaurants, bars, and small

specialty shops selling handicrafts to visitors. There is little left of the very small,

quaint, small-scale local fishing village that La Parguera was through the mid

1970s. Today, well over 100,000 visitors take advantage of La Parguera’s tourist

and recreation opportunities.

General Technical Report IITF-35

258

Box 29. continued

feet) and can be found to 41 meters (135 feet). It can take 20 years for a brain

coral to grow to the size of a human head.

Diploria strigosa (common brain coral) 

This is a medium-sized, hemispherically shaped, boulder-like coral, greenbrown in color. Its ridges and valleys are about the same width (4.5 to 10 millimeters), but are smaller than those of depressed brain coral. This species is

common to most reefs and can be found on the lagoon side, as well as in turtle

grass beds. They mostly inhabit water 6 to 12 meters (20 to 40 feet) deep, but

can be found to depths of 40 meters (130 feet).

For more information on these corals, see Almy Jr. and Carrión Torres

1963, Humman 1996, and Kaplan 1982.
Guide To The Ecological Systems Of Puerto Rico

259

Box 30. Gorgonians (sea fans)

Most corals are hard, wave-resistant, and nonflexible. Gorgonians or soft 

corals are just the opposite. They are soft, resilient, and bend or flex when

water moves over them. They do not produce the large extensive calcium carbonate structure typical of the hard corals. Gorgonians are more abundant in

the Caribbean than any other tropical water body. Some Gorgonians are typical of deep water, whereas others will be found in shallow waters, such as

lagoons, attached to soft sandy bottoms and in other protected back reef zones.

Many appear plant-like and have names like fans, plumes, pens, bushy, and

candelabra applied to their growth forms. Many are brilliantly colored purple,

rust, or yellow. The variable coloration in Gorgonians is produced by one or

more of the following: pigments in the polyps’ tissues, intracellular zooxanthelleae algae in the polyps’ tissues, or coloring minerals in the calcareous

spicules present in the colony.

They, like their hard coral counterparts, feed on plankton. They are different in that most will extend their tentacles during the day as opposed to the

hard corals, which are nocturnal feeders. They are often attacked by the colorful flamingo tongue snails. Gorgonians are not considered to be reef builders

as hard corals are, but they do add significant amounts of sand in the form of

shed calcium carbonate spicules. They are important as resting and feeding

sites for many reef animals, and they add textural and spatial richness to the

complex reef ecosystem.

Gorgonia flabellum (Venus sea fan)

This is a shallow water species with variable color ranging from yellow to purple or gray. Its common name suggests its fan-like shape. It produces an extensive group of flat interconnected branchlets. They grow to heights and widths

in excess of 1 meter (3 feet). Gorgonia flabellum prefers clear water and may

grow on shallow reef slopes, mostly in water less than 10.7 meters (35 feet)

deep. On occasion they will be found to depths of 30 meters (100 feet). They

are anchored to substrates by a trunk-like organ. When attached to rocky substrates they are virtually impossible to remove without a large knife or saw.

These are the most beautiful of the Gorgonians and are normally seen waving

gently back and forth as the water moves over and through the large fanshaped colony.

For more information on these corals, see Humman 1996 and Kaplan

1982.
General Technical Report IITF-35

260

Of concern to the environmental community in Puerto Rico is the rate of

population growth in the area and the extensive use of the marine resources at 

La Parguera. As a result, La Parguera has been designated a nature reserve by 

the Department of Natural and Environmental Resources. The Planning Board of

Puerto Rico has also designated the village a “zone of special planning” in further

recognition of its special marine resource value. However, a special marine fishery

reserve status has been locally rejected. This is unfortunate because zones of special planning do not appear to protect natural resources in Puerto Rico, and scientific evidence shows that marine reserves conserve biodiversity and replenish fish

stocks. According to Lubchenco (2001), population densities average 91 percent

higher and species diversity is 23 percent higher in reserves. The reserves work 

and they work fast. The no-take zones established in the Florida Keys in 1997 are

already showing measureable gains in the size of harvestable spiny lobsters and

grouper. For a review of the value of marine protected areas see Houde et al. 2001

and Roberts et al. 2001. Historical overfishing and the recent collapse of coastal

ecosystems are well documented for the Caribbean (Jackson et al. 2001). Virtually

all species of grouper and snapper are commercially extinct in the Caribbean, and

26 grouper species worldwide are being considered for listing as vulnerable to

extinction by the International Union for the Conservation of Nature and Natural

Resources. Local fishermen now have to take triggerfish and parrotfish, algae grazers that inhibit overgrowth of algae on reefs. Wire mesh fish traps generate less

than 10 percent of what they did in the mid to late 1900s (personal comments, La

Parguera fishermen 2000).

Puerto Rico’s coral reefs represent a valuable source of income and other

resources associated with tourism, marine fisheries, shoreline protection, and recreation. A significant number of islanders depend on coral reefs for part of, or their

primary source of income. An estimated $140 billion is generated by all Caribbean

reef uses (Jameson et al. 1995). Tourism is the fastest growing economic use of

coral reefs and is now a significant income producer in Puerto Rico. An estimated

100 million people visit the Caribbean yearly, many of whom engage in scuba 

diving, which is expected to generate in excess of $1.2 billion by 2005 (HoeghGuldberg 1999). Puerto Rico fishermen supply millions of dollars in fish-related

income to themselves, food stores, and restaurants throughout the island. These

fished species also serve as a healthy source of protein for the local diet. Nearly 

33 percent of the world’s fish species live in coral reefs. Reefs are no-cost, 

self-perpetuating natural fish farms, which produce vast quantities of high- quality

protein from sea water. Additionally, coral reefs serve as major buffers for storm-
generated waves and flooding. This protection minimizes storm damage to humanmade structures throughout the outer coastal fringe. They also help to protect the

other two vital marine ecosystems: mangrove swamps and seagrass beds that serve

as nursery grounds for the rich assemblage of species that inhabit the shallow

waters of the littoral zone. The costs associated with the loss of these essential

ecosystems and the services they provide would be enormous. These areas need to

be protected more than ever to maintain the present quality of the habitat and promote passive and active restoration in the near future. It is likely that conditions

will generally worsen in the future as the human population grows. If maximum

protection is not afforded soon, the losses will be even worse and could lead to

local and regional species extinctions. In general, the Caribbean is a low-species

region, and as Bellwood and Hughes (2001) have indicated, low-diversity regions

may be especially vulnerable to damage and destruction because they lack entire

families of coral species that might help the reef ecosystem to recover. They 

also reported that such a scenario, with resultant ecosystem disruption, recently

occurred in the Caribbean, where the decline of a guild of herbivorous fish (scarid

and acanthurid fishes) owing to overfishing, and a decline in the keystone grazer,

the black-spined sea urchins (Diadema antillarum) owing to disease, led to widespread algal blooms. Without adequate populations of algal grazers, reefs are likely

to be overgrown by algae, such as the genus Halimeda. These population shifts

produced a phase shift in ecosystem structure (fig. 78). For an excellent review of

the influences of overfishing and its effect on coastal ecosystems, see Jackson et al.

(2001). 

Recent research in reef larval connectivity and management strategies indicates

that management partnerships could be beneficial among Caribbean states (Roberts

1997). For example, core management partners for Puerto Rico would include the

United States and British Virgin Islands, and within the 2-month larval transport

area, would include St. Martin, Anguilla, and the Netherlands Antilles. Puerto Rico

would be a key partner for the Dominican Republic and Haiti. Each area would

need to set up local management protocols that would be designed to work within

the overall regional program devised by the international management partners. All

cooperators could create no-take reserves optimally spaced both for local benefits

and to support populations in other regional reserve systems. As Bellwood and

Hughes (2001) have indicated, protection of rich faunas of coral reefs will require a

greater understanding of their complexity and diversity. Species diversity variation

appears to be best explained by the area of available habitat. This suggests a need

for habitat protection at a regional scale, with coordination of reef conservation

Guide To The Ecological Systems Of Puerto Rico

261
General Technical Report IITF-35

262

Figure 78—The degradation of coral reefs on the north coast of Jamaica.

Two unrelated events, a hurricane in 1980 and the death of the algal grazing black spined sea urchin (Diadema antillarum) in 1983 resulted in a collapse in live coral cover (upper) and a population explosion of large algae

(lower) because the populations of grazing fishes have been overexploited.
programs international in scope. Bellwood et al. (2004) indicated that Caribbean

reef ecosystems are particularly vulnerable to phase shifts owing to lower species

richness and composition of important functional groups and that a major scalingup of management efforts is required in order to avoid further degradation of these

ecosystems.

In support of this international effort to preserve the ecological conditions of

the Caribbean, the Nature Conservancy has identified as part of their Caribbean

Conservation Plan 24 sites representing the greatest opportunities to harbor the

Caribbean’s biological diversity. These sites have been chosen based on their high

biological diversity, salvageability, position in the Caribbean current system that

will promote the distribution of larvae downstream, and their ability to receive

plankton, eggs, and larvae from upstream sources. In other words, each site, by

way of the interconnecting currents, will perform the dual role of being a “source,”

as well as a “sink” in the distribution of species. As a source, they will be dispense

nurseries, seeding the current with large quantities of urchin, conch, crab, lobster,

and fish larvae. As a sink, these sites will receive the larvae from other partner

sources (Stolzenburg 1999). In many cases, these sites will have associated seagrass beds and mangrove swamps. In the case of Puerto Rico, the island is viewed

as an important source of organisms for Parque Nacional del Este (sink) in eastern

Dominican Republic. Locations of sources in Puerto Rico and in the islands supplying Puerto Rico, the Virgin Islands, and other eastern Lesser Antilles islands

need to be determined in the next couple of years.

Healthy ecosystems should be a global concern. All countries and economies

depend on natural ecosystems, and these ecosystems are not bound by political

lines. Species migrate, air and water pollutants know no boundaries, and fisheries

collapse as a result of overfishing. Some experts indicate that we may only have 30

years to remedy our damaged ecosystems to prevent ecosystem failure.

For any group doing marine work in Puerto Rico, a variety of maps that provide the exact locations, sizes, and depths of reefs in the Fajardo and La Parguera

areas are available from both federal and commonwealth agencies as indicated in

the map section in the appendix.

Symbiosis

Many organisms in nature have developed unique beneficial symbiotic relationships with other organisms. Of significance in these relationships is the lack of 

similarity in the organisms involved. There are many classic terrestrial examples of

this phenomenon, such as ants and plants, protozoans and termites, rhinocerus and

Guide To The Ecological Systems Of Puerto Rico

263
General Technical Report IITF-35

264

tick birds, wasps and figs, and finches and iguanas. Coral reefs likewise provide

excellent examples of symbiosis in the marine environment. We point out that even

though these interactions are regularly referred to as symbiosis in the scientific literature, they are technically examples of mutualism. Symbiosis is a term that covers a broad range of organismal interactions, which includes competition, amensalism, neutralism, commensalism, and mutualism. Lewis (1985) has a continuum

that illustrates these relationships (table 24).

There are two general types of mutualistic symbiotic relationships—internal or

endosymbiosis, and external or ectosymbiosis. Both types abound on reefs. As

mentioned earlier, the key to the growth and health of coral reefs around the world

is the interaction between the coral polyps and their endosymbionts. In this case,

the primary algal symbionts are dinoflagellates (yellow-brown algae) from the

genera Gymnodinium and Amphidinium. The individuals of both genera are small

and spherical and live within the cells of the inner gut tissues of the coral polyps.

There may be 1 to 2 million algal cells per square centimeter of coral tissue

(Brown and Ogden 1993). They are referred to as zooxanthellae. The coral and

algae have evolved such close ecological ties that they rarely are found apart. The

presence of the algae provide the pigments found in the colors of the many otherwise transparent polyps. Because of the presence of these photosynthetic singlecelled algae, corals grow more during daylight hours than at night when the polyps

are actively feeding as carnivores on zooplankton. The mutualism involved in this

unique relationship relates to the fact that the corals provide dinoflagellate algae

with protection, a place to live, adequate access to sunlight for photosynthesis, and

metabolic waste products such as carbon dioxide and nitrogen molecules. The association allows algae to obtain compounds scarce in the nutrient-poor waters of the

tropics where warm surface waters overlie and lock in cold, nutrient-rich waters,

except in zones of upwelling such as in the waters off Perú and Ecuador. The corals

benefit by receiving oxygen as a byproduct of photosynthesis, and over 50 percent

of the organic molecules from algal food production are used by the polyps as

food. These relationships are true of both hard and soft corals.

Probably the classic example of ectosymbiosis on reefs is cleaning symbiosis.

In this case, cleaner organisms such as shrimp and small fish remove ectoparasites,

fungi, and diseased, injured, or dead tissue from larger client animals (hosts). The

results are thought to be mutually beneficial in that the host organism is rid of

harmful or unwanted matter, while the cleaner is furnished with food and is less

susceptible to predation. This relationship is very common among marine fish.
Interestingly, there are special behaviors that have developed as a form of

“communication” between cleaners and hosts based on body movements that serve

to initiate the cleaning interactions. Hosts will pose, specifically position themselves, or swim in specific areas where cleaners are located. Other cues may be

body coloration. Many fish have variable color forms on reefs. The cleaners

respond to these communications by inspecting a host through swimming closely

or physically contacting the host’s body (tactile communication). The areas where

cleaning takes place are referred to as cleaning stations.

One of the most interesting cleaning relationships is between shrimp and their

fish hosts. Some shrimp will be found in association with anemones, or in a small

hole in hard coral, such as the red and white barber shrimp (fig. 79). Fish approach

and the shrimp wave their antennae or bodies back and forth. Interested fish then

position the part of their body most needing cleaning in proximity to the shrimp.

This is usually the head and gills. The shrimp then mounts the body of the host and

removes parasites, other growths, and dead or injured tissues with its claws. The

fish remain almost motionless. Their gill covers are opened individually for inspection and cleaning. Fish will permit the cleaners to enter their mouth cavities without jeopardy of being eaten. This is even true of top predators such as barracuda.

Cleaning stations can often be spotted on a reef because of the “line-up” of fish

waiting for their turn to be cleaned. Fish will migrate to known cleaning sites in

large numbers. Hundreds of hosts may be cleaned in a day by a single cleaner.

At one time this phenomenon was thought to be an ecological novelty exhibited by just a few organisms, but we now know it represents one of the primary

behavior/health relationships on a reef and may be the best example of interspecific

cooperation among dissimilar animal groups in nature. There are dozens of fish

species that serve as cleaners, at least six species of shrimp, and even crabs. Most

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265

Table 24—Symbiotic continuum in terms of fitness of two associated organisms 

Competition -/-

Amensalism -/0

Agonism -/+

Neutralism 0/0

Commensalism 0/+

Mutualism +/+

- Fitness decreased.

0 fitness not affected.

+ fitness increased.

Source: Modified from Lewis 1985. 
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will have special anatomical adaptations that aid in cleaning. Many will be brightly

colored, which may serve as visual communication for identification and location.

Some cleaner species only clean in their juvenile phase; virtually all are physically

small, and most obtain additional food from other sources. All cleaners gain a high

degree of immunity from predatory fish. In fact, this relationship has been copied

by some predatory fish, in that they mimic cleaners as a way of attracting hosts,

which are then preyed upon. Not only are fish cleaned, but hosts also include rays,

marine turtles, marine iguanas, and sea urchins.

The health of many reef organisms is highly dependent on their being cleaned

regularly. Without regular cleaning, many fish will exhibit fungal growths, ulcerated sores, frayed fins, and ever-increasing numbers of ectoparasites, and wound

healing can be slower. There are implications for humans in this unique relationship in that fish with commercial value are also subject to these infections. It is

important that reef ecosystems, with their high diversity and specialized niches, be

kept as complete as possible. Knowledge gained from understanding these subtle

ecological relationships is now being applied to mariculture. Cleaning fish are

being introduced into commercial fish farms with the expectation that the health of

the commercial fish stocks can be better maintained without continued reliance on

chemical pesticides currently being used to control parasites.

Figure 79—View of beautiful barber shrimp, one of the reef’s best examples of cleaning

symbiosis. 

G. Miller
Coral Dieback

Coral reefs are some of the oldest marine systems on this planet. Most modern 

reefs are between 5,000 and 10,000 years old. Unfortunately, coral reefs are now

experiencing mass mortalities over a wide geographic range. The frequency of

these events and number of species and individuals being affected seem to be 

rising. Coral reefs throughout the tropical world are now exhibiting a variety of 

diseases causing dieback. These diseases include coral bleaching, rapid wasting

disease, yellow band disease, white pox, black band disease, sea fan disease, and

lethal orange disease. There are now at least 13 identified diseases of coral, three 

of which were newly reported in 1997. The identity of the causative agent is known

for only three of these diseases. No one knows whether this relates to decreased

host resistance, increased pathogen transmission (Harvell et al. 1999), or improved

worldwide monitoring of the reefs.

Coral throughout the Caribbean appears to be sickening at an accelerating rate.

Some of the most important of Caribbean coral species (Acropora) have been 

dying at increasing rates, and some reefs are now overgrown with algae. In some

instances, the causative agent(s) generating dieback is purely speculative, and

explanations for why this is occurring range from pesticide exposure and sewage

runoff, to light deprivation. These stressors may be making the coral susceptible to

pathogens. It may also be that a synergism is occurring; that is, two or more

causative agents may be interacting to produce an effect greater than their individual effects. It has recently been reported that there may also be a relation to events

taking place in the mainland of Africa that may be leading to one or more of these

dieback events. In sub-Sahara Africa, large clouds of dust are being generated and

blown to the western Atlantic and the Caribbean by trade winds. The causes,

according to the U.S. Geological Survey, appear to be droughts and overgrazing

3,000 miles (4800 kilometers) away. They estimate that several hundred million

metric tons of dust annually are being blown across the Atlantic. Interestingly, the

dust contains a nonmarine soil fungus (Aspergillus) that has been connected to the

decline in sea fans (Gorgonia flabellum). Sea fans now exhibit four colors, three

related to this illness: (1) dead with totally eroded flesh and only the skeleton

remaining, (2) area in dieback zone turning color, (3) deep purple as the coral

attempts to fight off the infection, and (4) normal healthy color. Research is now

being conducted to see if African dust and Aspergillus are present in the hard coral

skeletons laid down over the last 50 years on reefs in Puerto Rico and the U.S.

Virgin Islands.

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The rest of this section will only be concerned with one of the dieback diseases

known as “whiting disease or coral bleaching.” Coral bleaching was first described

by Yonge and Nicholls in 1928 from the Great Barrier Reef (Brown and Ogden

1993). The first coral bleaching in the United States was recorded in the Florida

Keys in 1911 and 1914 (Williams and Bunkley-Williams 1989). A series of bleaching events have been recorded in Neotropical Caribbean waters during the last 35

years. Various explanations have been suggested for the cause of bleaching events,

including changes in salinity, eutrophication, chemical pollutants, nitrate loading,

increased ultraviolet light, turbidity, and disease agents (Brown and Ogden 1993).

In the summers of 1987, 1990, and again in 1997–98, Caribbean reefs seemed to

turn white because of a higher than normal incidence of coral bleaching. The

1997–98 event was observed worldwide and was the worst on record. The main

culprit identified at the time for its cause was increased surface temperature of the

ocean. Since then, a number of other bleaching events have occurred elsewhere,

and most correlated well with elevated surface sea temperatures. In 1991, the

University of Miami (Florida) held a major workshop on temperature relationships

to coral and reached that conclusion. Sea temperatures in the tropics have shown

nearly a 1 oC (1.5 oF) increase in the past century. Another 1 to 2 oC (1.5 to 3 oF)

increase is projected for this century. Temperatures in excess of 30 oC (86 oF)

appear to be the threshold temperature that triggers bleaching events. An estimated

25 percent of the world’s coral reefs have already been destroyed or severely

degraded through problems arising from warming associated with climate change

(Roberts et al. 2002). Harvell et al. (2002) reviewed the importance of climate

warming and disease risks for marine biota. They indicated that climate warming

can increase pathogen development, survival, transmission, and susceptibility.

Major El Niño events appear to produce extensive bleaching episodes. During these

elevated temperature events, reef-building corals appear to be stressed, causing

them to expel millions of microscopic zooxanthellic dinoflagellate endosymbiotic

algae from their tissues. One explanation for why the algae are expelled relates to

possible creation of plant toxins as byproducts from photosynthesis. The algae are

vital to the well-being of the coral as they supply 63 percent of nutrients used by

the coral (Glynn 1991). 

The loss of the algae correspondingly produces a change in the color of corals,

as it is algae pigments that are primarily responsible for their host coral’s coloration. This loss of color then makes the coral appear whitish or transparent against

the white limestone skeleton that surrounds the polyp, thus the terms whiting 
disease or coral bleaching. Bleaching can be partial, or severe to the point of being

lethal to the coral. Most bleached corals are not dead, but they appear to 

have reduced viability. If corals do not regain their zooxanthellae, they will then

be more vulnerable to other stresses that can reduce growth and ultimately lead to

death. Repeated bleaching greatly reduces a reef’s general productivity. There have

been documented cases where a genus such as Millepora (fire coral) has totally 

disappeared from reef systems (Glynn and de Weerdt 1991). A wide variety of

corals and hydrocorals are now known to exhibit this response, including the 

common forms such as Millepora alcicornis (branched fire coral), Acropora

palmata (elkhorn coral), Montastrea annularis (common star coral), and Diploria

labyrinthiformis (depressed brain coral). All are typical of the reefs found throughout Puerto Rico and the Caribbean region. More than 60 species of corals have

been affected (Williams and Bunkley-Williams 1989). In 2005, coral reefs were

subjected to another major bleaching event precipitated by ocean warming in the

range of 3.5 oC (5 oF) above normal for a period of 6 to 8 weeks during September

and October. Estimates indicated bleaching occurred in at least 80 species. In

Culebra, researchers estimated up to 95 percent of small corals were affected, as

well as soft corals (extremely rare). This event also affected corals in other areas in

the Caribbean as cited by the United States Coral Reef Task Force. According to

Edwin Hernández, a University of Puerto Rico marine biologist, a lot of mortality

was observed. Staghorn (Acropora cervicornis) and elkhorn (Acropora palmata)

corals were especially hard hit. In some areas, 90 percent of their populations died.

This may result in a genetic bottleneck effect owing to their very low population

levels prior to the bleaching event. Both species are candidates for endangered

species status (Rust 2006).

Bleaching can take a toll on coral reproduction and their ability to recolonize.

In some instances, coral recolonization appears to start fairly quickly after a bleaching event, but it may take a long time for complete recovery as a result of interruptions of sperm and egg production. The new points of regrowth, although appearing

healthy, when checked for viable sperm and egg production, may exhibit only a 50-

percent production of gametes. Warm water appears to work two ways. One is the

full bleaching scenario and the second is the damage done to reproductive organs.

Even if bleaching does not occur, this double whammy greatly affects the potential

of corals to adequately reseed themselves when acceptable water temperatures

return.

There is potentially an even more important problem confronting reef recovery:

the likelihood of an increase in the frequency of warm water events in the future

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associated with global climate change. Without correct temperatures for reproduction and necessary adult populations to produce viable sperm and eggs, the longterm outlook for healthy and diverse coral reefs does not appear good. In addition,

once corals are lost, their zones of occupation may be overrun by macrobenthic

algae or other encrusting organisms, making recovery even more difficult. As

Hoegh-Guldberg (1999) indicated, “unrestrained warming cannot occur without

loss of coral reefs on a global scale.” He also indicated that based on a series of

models run to predict change in the frequency of bleaching events, the frequency of

bleaching is set to rise rapidly. The highest rate of bleaching event increase is projected to occur in the Caribbean, and within 30 to 50 years bleaching is likely every

year. Table 25 reviews the changes in bleaching events as a function of temperature

change.

Although there is good correlation with high water temperatures and coral

bleaching, there is still some uncertainty on this issue. Research continues in order

to find one or more verifiable cause-and-effect relationships. Some experts feel that

many of the degraded reefs and their associated dieback are a function of their

proximity to developed or fast-growing sections of the world, such as the keys in

Florida or the islands of the Caribbean, and that most remote oceanic reefs do not

appear to be imperiled. Those already damaged by anthropogenic impacts and with

weak ocean currents, which cannot keep water temperature from reaching the

bleaching threshold, have shown the worst bleaching episodes. Recent paleontological evidence shows that Caribbean reefs have been remarkably stable as far as

community structure is concerned. The same dominant and rare species of coral

have remained relatively constant over the past 220,000 years. However, in the past

few decades, species shifts have been observed that suggest an unnatural, nonrandom, possible relationship to human activities (Stokstad 1991).

As a result of all the scrutiny given to zooxanthellic coral, new insight may be

emerging with a not-so-grim outlook for bleached corals. Shedding of the symbiotic algae may be a seasonal phenomenon during which approximately 75 percent

of the zooxanthellae are expelled without harm. The remaining 25 percent is not

enough to give coral its true color, thus it appears white. Later, the algae can be

replenished or new algae taken on by the coral. Research underway is looking to

assess seasonality, variability in algal species and host specificity, variation in

zooxanthellae concentrations, temperature thresholds, and depth and light variations. Hopefully, from this array of current research, conclusive answers regarding

the cause of coral bleaching will be forthcoming in the near future.
For further reading see Aaxelrod and Hamilton 1981, Amadon 1967, Atwood et

al. 1992, Benchley 2002, Bunkley-Williams et al. 1991, Chaplin 1972, Clifton

1997, Connell 1978, Darwin 1842, Deloach 1993 and 1997, Fagoonee et al. 1999,

Foster 1985, Gaski 1988, Goenaga 1990, Goenaga and Cintrón 1979, Goenaga et

al. 1989, Goreau et al. 1979, Greenberg 1979 and 1980, Griffith and Williams

1985, Hartman 1973, Hughes 1994, Humman and Delvach 2002, Jaap 1984,

Kaplan 1988 and 1998, Kjerfve 1998, Lang 1974, Lehmann 1983, Lieske and

Myers 2002, Limbaugh 1961, Littler et al. 1989, Littler and Littler 1995, Losey

1972 and 1974, Losey and Margules 1974, Lugo et al. 2000, McLaughlin and Zahl

1966, Muscatine and Porter 1977, National Aeronautics and Space Administration

2001, Odum 1971, Pennisi 1997, Peters 1997, Pike 1989, Poulin and Grutler 1996,

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271

Table 25—Coral bleaching issues and temperature change 

Will coral bleaching Bleaching events are projected to increase in frequency until they

increase in the future? become yearly events by 2050 in most oceans. 

In some areas (e.g., Southeast Asia and Caribbean), bleaching is 

expected to occur more rapidly (by 2020). In 20 to 40 years 

from now, bleaching is projected to be triggered by seasonal 

changes in water temperature and will no longer depend on 

El Niño events to push corals over the limit. 

This will become critical as bleaching events exceed the frequency at which corals can recover from bleaching-related 

mortality and lowered reproductive capacity. 

Evidence suggests that coral reefs will not be able to sustain this 

stress, and a phase shift to algal-dominated benthic communities 

could result.

Why were there few Increases in sea temperatures have become more critical since 

coral bleaching events 1980, when El Niño disturbances began to exceed the thermal 

prior to 1980? tolerances of corals and their zooxanthellae.

Prior to this, El Niño or other disturbances rarely exceeded the 

thermal limits of corals and zooxanthellae.

Why are corals Before recent increases in sea temperature, corals and their 

growing so close to zooxanthellae lived in water that typically rarely rose above

their thermal limit? their maximum thermal limits. 

Owing to the increases in sea surface temperature over the last 

hundred years (1 oC [1.5 oF]), corals may be just below their 

upper thermal limits. 

Prior to this warming, corals would have always been a degree or 

two below these critical levels. 

Proximity of corals to thermal limits is tacit evidence that they 

have not been able to acclimate to these increases. 

There has been little evidence of thermal adaptation (genetic 

change) of corals in these areas over this period, although there 

may be signs of species shifting taking place.

Source: Modified from Hoegh-Guldborg 1999. 
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Ray and Grassle 1991, Rogers 1974, Sale 1991, Sarokin and Schulkin 1992,

Sebens 1994, Stryowski and Bonem 1993, Talbot and Wilkinson 2001, U.S

Department of the Interior, Geological Survey 1999, Veron 1995 and 2000, and

Wilkinson and Beddermeier 1994.

Special underwater references—

There are three references for fish and invertebrates of coral reefs that can be taken

with you in a boat or even underwater while diving or snorkeling. Two are plastic

6- by 10-inch sheets, which can be hung around your neck or wrist, that cover fish,

corals, and other marine invertebrates common to Caribbean reefs. The other is a

complete book printed on plastic paper (65 pages) devoted to fish. All three are

useful field guides for students and recreation divers. The Fishwatcher’s Guide

book by Chaplin was cited earlier. See the appendix for the source of color educational wall charts depicting the coral reef ecosystem and the fishes of Puerto Rico.
Chapter 7: Disturbances in Puerto Rico

and the Caribbean

Hurricane Effects on Ecosystems

Hurricanes are powerful tropical storms that start as summer depressions in the 

warm waters off the west coast of Africa. The westerly trade winds push the

depression toward the Neotropics north of the equator and as it rides over large

expanses of warm water it picks up energy and windspeed (fig. 80). The origin 

of the English term “hurricane” derives from the Taíno Indian word for hurricane,

which was Juracan. Juracan was used in reference to their god of evil whose anger

produced fierce winds. These storms can affect vast areas of marine and terrestrial

ecosystems. They constitute one of the most devastating natural disasters and are

now costing the United States $5 billion per year (Bengtsson 2001). In 1998,

Hurricane Mitch killed at least 10,000 people in Central America. There are five

categories of hurricanes based on windspeed (table 26). If the winds associated

with the storm reach 120 kilometers per hour (kph) or 75 miles per hour (mph), it

is a Class I hurricane (called typhoons or cyclones in Indo-Asian waters). As the

storm reaches the Lesser Antilles where water temperatures may be higher, the

strength of the storm can build to a Category 2 moderate hurricane, with windspeeds of 154 to 176 kph (96 to 110 mph), or a Category 3 extensive hurricane

(178 to 208 kph or 111 to 130 mph). Any hurricane of Category 3 or higher is 

considered major. On occasion, hurricanes and tropical storms also spawn in the

Caribbean Sea and Gulf of Mexico and can be equally destructive. The years 1995

to 2000 experienced the highest level of North Atlantic hurricane activity in the

reliable weather record. The past 6 years have seen a doubling of overall activity

and a 2.5-fold increase in major hurricanes. This increase has produced a fivefold

increase in hurricanes affecting the Caribbean. This present level of activity is 

projected to persist for another 10 to 40 years (Goldenberg et al. 2001). The 2005

hurricane season was the greatest on record with 26 named storms, 13 of which

were hurricanes. An estimated $125 billion in damage was associated with just 

four of the hurricanes.

Hurricanes impact the Caribbean area annually with the highest frequency

occurring in September. More than 70 hurricanes have passed over Puerto Rico

since the early 1700s. For a review of the history of hurricanes in Puerto Rico,

see Quiñones (1992).

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Terrestrial Effects

In September 1989, Hurricane Hugo roared into the northeast section of the 

Caribbean and half a dozen islands received direct hits, including St. Croix in the

U.S. Virgin Islands and the east end of Puerto Rico. At times, winds were 224 kph

(140 mph - Category 4 hurricane). These violent winds can be devastating to

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Figure 80—Atlantic hurricane development and trajectory patterns.

A

B

Satellite image of Hurricane Marilyn as it passed over the U.S. Virgin

Islands on September 16, 1995.

Satellite image of two hurricanes, a tropical storm, and a tropical wave

over the Atlantic Ocean. All these systems orginate off the coast of

Africa—as illustrated by the tropical wave on the right of the image—

and travel in a westerly direction towards the Caribbean or the North

American mainland. The Caribbean is on the bottom left of the image

shrouded in clouds. 

Photo: Courtesy of

NOA

A

Courtesy of

NOA

A
forested ecosystems. In addition to extreme wind velocities, vast quantities of rain

are associated with these storms adding stress to weight-bearing parts of plants,

such as stems and roots. Frequently, stems snap and trees fall as a result. Sections

of the El Yunque National Forest received more than 300 millimeters (12 inches) of

rain as the storm’s eye passed just east of the forest. Hurricane Hugo produced in

excess of $9 billion in damage and disrupted the lives of 2 million people along its

path through the Caribbean and into the Southeastern United States. Puerto Rico

suffered an estimated $2.5 billion in property damage.

Hurricanes are equally destructive to natural ecosystems. Plants, animals, and

habitats are stressed, damaged, or destroyed depending upon the intensity and duration of the storm. This is true of both terrestrial and aquatic systems. In many

instances, habitats may be permanently altered, whole populations may disappear,

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Table 26—Categories of hurricanes based on windspeed and the Saffir-Simpson Scale 

Storm surge 

Storm (above normal Possible

Category Windspeed nomenclature tide) damage

kpha

(mph)b

1 120 to 152 Minimal or 1.2 to 1.5 Mainly to tree branches,

(75 to 95) weak (4 to 5) mobile homes damaged, 

power lines down

2 154 to 176 Moderate 1.8 to 2.4 Tree blowdowns, heavy

(96 to 110) (6 to 8) damage to mobile homes, 

roofs off buildings, 

some local and regional 

flooding

3 178 to 208 Extensive or 2.7 to 3.7 Tree blowdowns, structural

(111 to 130) strong (9 to 12) damage to buildings, flooding 

can be widespread

4 210 to 248 Killer or very 3.9 to 5.5 Major vegetation destruction,

(131 to 155) strong (13 to 18) signs down, major structural

damage to buildings, major 

flooding and beach erosion

5 In excess of 248 Catastrophic >5.5 Severe damage to buildings 

(in excess of 155) or devastating (>18) of all types, all vegetation 

types damaged, low-lying 

buildings can be washed away,

severe beach erosion and 

nearby coastal roads damaged

and underwater, heavy damage

to phone and electric delivery

a Kilometers per hour.

b Miles per hour.
and vital food and nesting resources may be lost for an indefinite period. For example, more than 200 landslides were recorded within the El Yunque National Forest

as a result of Hurricane Hugo (fig. 81). Evidence indicates that hurricanes may be

the most important factor controlling populations and ecosystem dynamics in most,

if not all, islands in the Caribbean. In the El Yunque National Forest, and specifically the road to the forest (Route 191), the canopy was opened up as if a can opener had taken the top off the forest. The 12.2-meter (40-foot) leafy branch-covered

archway that led up to the high canopy was totally opened to the sky. The road 

now receives full sunlight, and much of the vegetation still exhibits scars from the

severe effects of the storm in 1989. In the hardest hit areas, 60 percent of the trees

were downed or damaged, and 27 percent of the endangered Puerto Rican wild 

parrot population was lost.

In general, human systems may be more subject to damage than those in

nature. The big difference is that in 6 months or a year, human systems are rebuilt

and no hurricane effects are observable. This is not the case in natural systems.

Nature rebuilds much more slowly because it is not buoyed up by vast amounts of

cash, energy, and out-of-system resources. Hurricane damage in nature generally

causes a crash in stored energy and resources, and will require time for the natural

processes to replace them via complex successional and ecosystem development

processes.

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Figure 81—Effects of Hurricane Hugo in the El Yunque National Forest. 

A.E. Lugo
Hurricanes on average occur four to five times a year in the Caribbean. Puerto

Rico is seriously affected about every 21 years, and these storms appear to have

direct effect on the size of trees, biomass accumulation, and species diversity. Some

experts have described forests in these areas as “hurricane disturbance systems”

because of their ability to quickly alter ecosystem processes as the storms drastically alter animal and plant populations. As we are now in a period of global 

climate change, there are important questions to be answered: With a predicted

increase in the frequency and intensity of storm events, will severely damaged 

systems have enough recovery time to attain prehurricane status before the next

storm strikes? Is it conceivable that some areas may remain in some stage of 

succession indefinitely?

What changes do hurricanes produce? The following is only a partial generic

list.

➢ Complete felling of some trees resulting in vast amounts of biomass 

being shed and root balls forming

➢ Partial to complete deleafing and debranching resulting in massive 

litterfall

➢ Alteration of nutrient cycles

➢ Elimination of reproduction for some individuals

➢ Interruption of some phases of growth

➢ Loss of some of the local animal pollinators or seed vectors

➢ Vastly altered amounts of light throughout the forest

➢ Stresses to roots via altered water regime and rocking/twisting of 

aboveground parts

➢ Landslides

➢ Alteration of mortality patterns and species turnover

➢ Alteration of succession patterns and forest regeneration

➢ Light-requiring species respond rapidly

➢ Flood damage associated with streambeds and flood plains related to

species presence and coarse woody debris increases

➢ Reduction in some forest invertebrates

➢ Altered population structure of vertebrates (some enhanced, others

declined, depending on species niches—frog, lizard, and bird responses 

differ). In general, they exhibit a decrease, but some species may 

rebound rapidly or actually benefit

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Guide To The Ecological Systems Of Puerto Rico
For detailed reviews of ecosystem, plant, and animal responses to hurricanes in 

the Caribbean and long-term responses of Caribbean ecosystems to disturbance, see

the special issues of Biotropica by Walker et al. 1991 and 1996.

Over a long period, hurricanes may have produced an adaptive ecosystem

response in areas where they are frequent. For instance, compared to tropical rain

forests in South America, there are no emergent trees present in Puerto Rico’s

forests (fig. 82). Areas with high frequency of hurricanes tend to exhibit flatter

wind-sculpted canopies.

The following list identifies other possible adaptive responses.

➢ Forests exhibit high species dominance.

➢ Similar numbers of species are present per unit area.

➢ Low biomass accumulation because they tend to be in a constant state 

of recovery.

➢ Species that are present tend to be highly resilient.

➢ A higher percentage of young individuals and pioneer species are 

present in forest stands.

It is estimated that possibly 12 million hurricanes have passed over Puerto Rico

since plants covered its complex landscape (A.E. Lugo 2001, personal comment).

Clearly, hurricanes represent a major selection factor on species and ecosystems.

The species combinations found on many Caribbean islands are likely those that

are capable of thriving under natural stress in hurricane-mediated disturbance conditions. For additional information on hurricane effects in a period of climate

change, see Lugo (2000).

Marine Effects

Hurricanes can play havoc on coastal ecosystems including mangrove swamps, 

submerged seagrass beds, and coral reefs. The strong winds generate powerful deep

waves that can crash into these ecosystems for hours or days. They also produce

extensive storm surges. When Hurricane Hugo struck eastern Puerto Rico, waves 

in the 3.9-meter (13-foot) size class were common. The energy of the waves can

physically break apart the species present and alter the normal physical, chemical,

and light relationships required for these systems to be maintained. As was the case

in the terrestrial ecosystems, vast quantities of freshwater are directly deposited

into these systems. Nearby streams that may have been intermittent carry vast

quantities of freshwater, sediment, and organic matter into these coastal ecosystems. Alteration of pH, salinity, and turbidity may have drastic effects on the physiology of plants and animals present.

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The following is a partial list of the kinds of changes hurricanes can produce in

coastal ecosystems.

➢ pH

➢ Salinity

➢ Turbidity

➢ Physical breakage of live organisms and deposition of debris piles

➢ Scouring

➢ Alteration of light regimes

➢ Deleafing

➢ Sand blasting

➢ Leaf chlorosis

➢ Organic deposition (natural and human)

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Guide To The Ecological Systems Of Puerto Rico

Figure 82—Long-term hurricane effects on canopy design in (a) hurricane-prone vs. (b) non-hurricane areas. Theoretical diagram of forest

structure in relation to the hurricane factor showing differences in crown sizes, canopy-stem ratios, boundaries of crowns in aerial views.

(a) Hurricane type (Dominica, Puerto Rico), (b) Lowland equatorial type (Costa Rica).
➢ Sedimentation/inundation

➢ Chemical runoff

➢ Interruption of food chains

➢ Temperature change

➢ Depth increases or decreases

➢ Oxygen and nutrient changes

➢ Alteration in dominant species populations or phase shift to algae 

dominance

➢ Permanent changes in structure and function if severe and repetitive

Hurricanes usually damage shallow coral reefs most because of the wave 

damage inflicted on Acropora palmata1 (elkhorn coral) and Acropora cervicornis

(staghorn coral). Many other corals, such as soft corals, may suffer from sedimentation and burial by coral rubble because they are sedentary. Following Hurricanes

Hugo and Georges, the east end of Puerto Rico around Culebra suffered almost

total destruction of elkhorn coral. Virtually all colonies over 1 meter (3 feet) were

fragmented or overturned (fig. 83). Porites spp. (finger coral) and staghorn coral,

along with elkhorn coral formed large piles of coral rubble, which covered extensive areas of living coral (USDI Geological Survey 1999). Table 27 summarizes

some of the common hurricane effects observed on coral reefs.

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Figure 83—Hurricane-produced damage on coral reefs in the Caribbean.

G. Miller

1 See appendix 1 for Common and Latin names.
Seagrass beds can suffer from severe scouring produced by waves and currents.

Many beds can be buried under vast amounts of sediments dislodged at sea or

deposited from rain-induced erosional disturbances on land.

Mangrove swamps can be structurally broken apart, deleafed or blown over,

and become susceptible to infections. Some areas will be either inundated with sea

or freshwater, both of which can produce major changes in forest composition and

altered succession patterns. Early growth after hurricanes is likely to be rapid

because of full sunlight and the extra nutrients made available from the decomposing debris produced by the storm. Mangrove swamps exhibit traits of disturbanceprone ecosystems such as environmental tolerance to stress, resilient growth, and

early reproduction, all of which should promote rapid recovery. Roth (1997) stated

that the even-agedness of many Caribbean mangrove stands, as well as their youth

and generally small stature, may be attributable, in part, to posthurricane origins.

Mangrove canopies in the Caribbean are about 50 percent shorter than their counterparts in Asia where hurricanes are infrequent.

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Table 27—Common hurricane effects observed on Caribbean coral reefs 

Feature Effect

General damage Highly variable, from little to none, to total destruction over short 

distances, with shallow water portions of reefs generally experiencing 

highest damage

Key species of hard Branching corals: Acropora palmata (elkhorn), Acropora cervicornis

coral damaged (staghorn), Porites spp. (finger)

Resistant species Montastrea (boulder star coral) and Diploria (brain corals)

Fish Generally short-term to minor changes, many migrate to less disturbed 

reefs or protected areas and deeper water; some population decrease likely

Predation Likely to increase for those species that have lost cover, grottos, caves, 

etc., or protective background coloration when they spend more time in 

unprotected open water

Algae Some lost owing to buildup of coral and sediment overburden; more 

habitat exposed/created owing to rearrangement of the reef creating new 

surfaces for colonization

Gorgonians Burial and abrasion likely, can lead to major loss of colonies, but 

regeneration can be rapid

Echinoderms Shallow water residents most affected, those in back reefs and protected 

lagoons or deeper zones may escape damage or population depressions

Indirect actions New territories involving coral, algae, and fish may lead to low survival 

rates of coral or loss of fish if the new habitat conditions do not meet 

their necessary spatial needs or position on the newly reconstituted reef

Regeneration rates Dominant branching species likely to regrow rapidly from upright survivors 

and fragments, creating sizeable populations in 15 to 20 years. Most reef 

productivity is the result of free-living algae, which are rapid recolonizers 

of newly exposed hard substrates

Source: Modified from Lugo et al. 2000.
For further reading see Basnet et al. 1992, Hughes 1994, Kjerfe et al. 1997,

Lugo et al. 2000, Odum 1970, Robinson 1997, Weaver 1989 and 1999, Wiley and

Wunderle 1993, Woodley et al. 1981.

High Rainfall, Drought, Landslides, and Fire Events

The climate of Puerto Rico is cyclic (fig. 84). Decades of increasing annual rainfall 

alternate with decades of decreasing rainfall. Because of these dramatic oscillations, mean rainfall values are not useful for the purpose of planning water use or

understanding ecosystem and landscape functioning. Rainfall is a main driver of

primary productivity, water cycle, streamflow, aquifer recharge, soil oxygen

content, sediment transport, mass wasting, lowland flooding, water supplies for

human consumption, and so forth. Given all these important roles of rainfall, the

cyclic swings of annual rainfall have enormous implications for the events that we

see unfolding on landscapes. The effects of either too little or too much water are

modified by human activity. Human activity can increase the vulnerability of the

landscape to too much rain or drought, or can create situations where natural

processes occur at greater intensities. We will illustrate this in the discussions

below.

One effect of human activity on rainfall events is the long-term global change

now picking up speed in the world. Scatena (1998) and others reported evidence of

decreasing rainfall in Puerto Rico over the last 100 years. Such reductions in rainfall, coupled with increased urbanization of Puerto Rico and the canalization of

rivers would tend to dry up the island and change the islandwide distribution of

plant communities. Others suggest that hurricane frequencies will increase in the

future. Increased hurricane frequency also impacts vegetation and rainfall in a

direction opposite to that of a periodic decrease in rainfall. These changes, if they

occur, will fundamentally change the response of the biota to its environment and

the welfare of humans on the island. However, we have no idea how global change

processes will interact to create the ecosystems of the future. Keep these matters in

mind as we describe some examples of excessive rains, drought, fires, and landslides in Puerto Rico and elsewhere in the Caribbean.

Periodically, tropical waves, northern fronts, or hurricanes dump large quantities of water on Puerto Rico. Rainfall events of 25 millimeters (1 inch) per hour

lasting for many hours cause floods in the lowlands and landslides in the uplands.

These events are common to islanders who suffer the consequences of washed-out

roads, flooded homes and highways, interrupted water and power services, and so

on. Of interest are the effects of these events on the ecology of Puerto Rico.

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Figure 84—

Cyclic climatic rainfall patterns in Puerto Rico.
High rainfall events produce many important functions to the island ecosystems. For example, they recharge soils and aquifers with moisture, thus mitigating

and postponing drought. They produce large quantities of sediment, and transport

sediments from montane regions to coastal plains. In so doing, high rainfall events

help shape the land, river, and stream channels, fertilize flood plains, reduce salinity in estuaries, serve as signals for the reproduction and migration of organisms,

and generally rejuvenate the landscape.

Landslides are a product of high rainfall events. If rainfall exceeds 200 millimeters (8 inches) in a day, landslides are triggered. Landslide formation increases

with rainfall, poor land use practices, and particular geologic formations that are

more prone to sliding than others. In a small watershed, 26.4 square kilometers

(10.2 square miles) in Puerto Rico, Larsen and Roman (2001) counted 2,000 landslides since 1820 when forest clearing began. These landslides produced 660,000

cubic meters/square kilometer (23.3 million cubic feet) of sediment or the equivalent of lowering the mean surface level of the watershed by 6.6 centimeters (2.5

inches). These numbers are staggering and represent an extreme case of anthropogenic disturbance in the tropics.

In December 1999, excessive rains fell along the north coast of Venezuela near

Caracas, the capital city. Nine hundred and eleven millimeters, or 36 inches, fell

over 2 days—about 2 weeks after the region had experienced 200 millimeters or 8

inches of rain in 2 days. The magnitude of the subsequent floods, landslides, mudflows, and avalanches was without known precedent, and over 19,000 people were

killed. Boulders weighing 300 to 400 tons were moved to the coast by these events;

buildings were covered by debris, and the shape of the coast of Venezuela changed.

Such is the force of nature when extreme natural events combine with large human

populations.

The formation of landslides has repercussions to vegetation (Walker 1999).

Landslides remove all vegetation from the surface of the landscape affected and set

succession back to primary succession. Plant succession usually starts in nutrientpoor soils and unfavorable growth conditions such as impermeable surfaces, high

light intensity and temperatures, and high rates of runoff. The plants best adapted

to these conditions are lower vascular and nonvascular plants, ferns, and grasses.

Arrested succession is common on landslides. This means that the orderly change

of plant species stops and a particular stage retains dominance over a site. Usually,

ferns and grasses dominate these arrested successions. However, on favorable sites,

succession proceeds to a forest. Studies in the Luquillo Mountains show that after

60 years, a native forest can occupy the site where landslides occurred previously.

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The tropics are usually associated with rain forests and abundance of rainfall.

However, about half of the tropical forest area is dry forest where organisms are

limited by water. Drought is common in these environments. The subtropical dry

forest life zone constitutes the driest conditions in Puerto Rico, and rainfall as low

as 300 millimeters (12 inches) per year has been recorded in some locations. When

drought occurs, plants wilt, leaves fall, the tops of tree branches die off, and many

trees are killed. Events such as these are common in the dry tropics, but they also

occur in the wet tropics. In the Luquillo Mountains, for example, severe droughts

occur with frequencies that approach one per decade. In 1992, such a drought

occurred and scientists could not find any deleterious effects on trees. This suggests

that the native flora of Puerto Rico is adapted to periodic drought. It is possible for

all of Puerto Rico to be under the influence of recurrent droughts. During this time,

water shortages and rationing are common islandwide.

Regardless of the recurrence of drought events, fire is not a natural event in the

island. We know of no native plant community subject to fire or adapted to fire.

However, in 1999, the Fire Department reported 2,975 wildland fires in Puerto

Rico (fig. 85). The cause of nine of the fires was lightning; the others were set by

humans. Most of those fires occur near roads and in zones with less than 1500 millimeters (60 inches) of rainfall. Moreover, because of the introduction of many fireadapted exotic grasses from Africa to Puerto Rico, we now observe the development of new fire-dependent ecosystems in Puerto Rico. These ecosystems are near

highways and roads, and are dominated by alien grasses. These ecosystems are

expanding at the expense of native ecosystems not able to survive the new fire

regime introduced by human activity.

For further reading see Larsen and Santiago Román 2001, Larsen and Torres

Sánchez 1998, Larsen et. al 2001, and Myster and Walker 1997.

The Urban Forest Interface

As human activity continues to increase in Puerto Rico, it becomes the major disturbance regime in the island. We end the section on disturbances by focusing on

the urban forest interface in Puerto Rico.

What is a greenspace or greenway? Green open space, green natural area,

green travel space, urban trail system, all describe a greenway or greenspace.

Greenways may be linear parks that have large irregular perimeters that frequently

conform to some special geographic feature such as a river, a steep mountain, or

the interface zone of a city. Greenways can effectively serve as corridors for foot

and bike traffic, or be specialized recreation corridors for jogging, biking, and bird

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Figure 85—Fires in Puerto Rico.
watching. They frequently connect commercial and residential nodes, tourist attractions, education facilities, and so forth. In many areas, they are used as “soft engineering” approaches to increasing water quality whereby vegetative buffers help to

filter out pollutants. They also slow and store floodwaters and help to reduce sediment loss. Greenspaces and greenways are also very important because they serve

as urban wildlife refuges and migration corridors thereby ensuring some opportunity for humans to coexist with wild plants and animals. Many serve as focal points

for the teaching of environmental biology to children in urban schools. Their presence may also substantially enhance the property values of nearby businesses and

residential areas and increase the liveability of an urbanized landscape.

Puerto Rico is currently experiencing rapid rates of urbanization throughout

most low-elevation areas of the island. San Juan, as of 2002, has only 16 percent

greenspace remaining, and that percentage appears to be declining rapidly (fig. 86).

The rate of loss of greenspace is now critical because, at present rates of development, virtually all greenspace will be lost by 2025.

Today, in the municipality of San Juan, there are a couple of significant forest

inholdings that represent the last opportunities for permanent greenspace to be set

aside. There are about 27 000 hectares (72,700 acres) of undeveloped greenspace in

the six municipalities of greater San Juan, with most of it in their southern boundaries. There is currently a proposal being discussed that could link some of these

small contiguous urban forest remnants to others in the adjacent municipalities.

These areas were all previously deforested, but are currently in various stages of

secondary succession and have great value as a wildlife refuge for native species,

especially birds, amphibians, and reptiles. There are about 200 hectares (500 acres)

controlled by the University of Puerto Rico on the urban campus shared with the

Department of Agriculture, the USDA Forest Service, International Institute of

Tropical Forestry, and the Botanical Garden in Río Piedras. This space could serve

as the locus for development of a major greenspace for that area.

A field trip through this area will allow you to see the urban forest interface

and see the many values that greenspaces such as this have, including:

➢ Wildlife refuge

➢ Plant refuge

➢ Protection of headwater streams

➢ Reduction of noise 

➢ Reduction of flood damage

➢ Filtering urban water sources

➢ Education/research

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Figure 86—Urban forest map of greater San Juan.
➢ Bird watching

➢ Urban greenspace recreation

➢ Air pollution reduction 

➢ Urban climate modifier

Things to be observed are:

➢ Various successional species and stages of successional development

➢ Hilltop-to-flood-plain transect

➢ Urban/forest interface

➢ Río Piedras flood plain

➢ High pollution zone near business district with oil contamination and 

solid wastes

➢ Filtered water on natural flood plain

➢ Flood plain plant zonation

➢ Lianas

➢ Low epiphyte presence

➢ Root balls–hurricane damage

➢ High light demanding plants–storm gaps and early-succession species 

with low survival of adults and seedlings

➢ Nitrogen fixers

➢ Alien plant species

➢ Plant adaptations to reduce predation

➢ Poison plants Urtica and “Molinero’s”—spiny trunks

Controversies associated with sites like this include:

➢ University growth–recreation (satellite campus)

➢ Río Piedras public use zone

➢ Continued demand for space for economic growth

➢ Little historical precedent for protecting urban greenspaces in Puerto

Rico

➢ Zonation conflicts

➢ Mindset toward jobs, growth, and political ambitions (is growth 

always good?)

➢ Will greenspace development have enough economic/community 

value to justify permanent set-asides?

➢ Few jobs produced

➢ No products for sale

➢ Little, to no tax revenues will be generated

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Greater San Juan could adopt a “hectare for hectare” (acre for acre) mindset.

That is, for every hectare developed, a hectare is set aside and protected or

restored. This is the last easy opportunity for the creation of urban greenspace for

the many communities involved. In a few years, these green remnants will be

paved over. Future generations will have little opportunity to identify with nature,

to enjoy the sweet smell of a working forest, or to enjoy the beauty of fish in a

stream. This is a small area to set aside compared to the many benefits current and

future generations will receive from these greenspaces.

One of the great challenges throughout the world’s urban areas is how to make

communities more livable. Invariably, one of the most meaningful options is the

designation of greenspaces. Many cities are in many ways urban deserts, and it is

only in greenspaces such as parks, urban forests, and linear riparian zones along

rivers that urbanites are provided with opportunities to get some relief from life in

the urban jungle.

For further reading see American Forests 2002.

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Chapter 8: Environmental Organizations

and Environmental Infrastructure

The El Yunque National Forest and the International 

Institute of Tropical Forestry

There are 155 national forests in the U.S. National Forest System, and the El 

Yunque National Forest (EYNF) is the only tropical rain forest. The EYNF is

among the smallest forest units in a U.S. National Forest System that encompasses

over 77 296 641 hectares (191 million acres). It is, however, the largest forest

reserve in Puerto Rico. This unique forest, which, until 2007 was called the

Caribbean National Forest, is located on the eastern side of Puerto Rico in the 

sierra de Luquillo Mountains. The forest is the only national forest that is also an

experimental forest, the Luquillo Experimental Forest. As such, it is dedicated to

research, as well as other national forest functions.

Owing to the prevailing trade winds and orographic effects, rainfall is plentiful

in the EYNF. Average rainfall throughout the forest is 3000 millimeters (120 inches), but some areas in the forest receive more than 5000 millimeters (200 inches) 

of rainfall per year. This is equivalent to more than 378 billion liters (100 billion

gallons) of water. It is the “rainiest” national forest and consequently it is the only 

forest with no forest fire problem. Although this forest encompasses only 11 322

hectares (28 000 acres), it is big in terms of biodiversity. The EYNF has more

species of trees than are present in all the other 154 national forests together. Some

240 tree species are native to the area. Twenty-six species are endemic to the forest,

and another 45 species are found only in Puerto Rico. Its elevation ranges from 

100 to 1077 meters (330 to 3,533 feet). There are seven peaks over 930 meters

(3,050 feet) high with El Toro (the bull) the tallest at 1075 meters (3,526 feet). It

constitutes the largest single area of natural managed forest on the island.

The United States inherited this forest when Spain ceded Puerto Rico to the

United States as a result of the settlement of the Spanish-American War. The original inholdings of forest were set aside by decree in 1876 by the King of Spain, and

as such, this is one of the oldest reserves in the hemisphere and compares with the

date of the designation of Yellowstone National Park (1872), the United States’

first national park and the world’s oldest national park. Its original size was 4920

hectares (12,300 acres) and this royal designation saved it from deforestation,

which ultimately produced more than 90 percent loss of forest cover in Puerto Rico

by the early 1900s. In 1903, President Theodore Roosevelt designated the area the

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Luquillo Forest Reserve, and it was later incorporated into the U.S. National Forest

System. In 1946, the Puerto Rican government designated the forest a commonwealth wildlife refuge, because it provides habitat for 120 vertebrate species such

as birds, bats, lizards, amphibians, and fish. The forest has 68 bird species, including 9 island or EYNF endemics: The Puerto Rican parrot,1 Puerto Rican lizard

cuckoo, green mango hummingbird, Puerto Rican emerald hummingbird, Puerto

Rican tody, Puerto Rican woodpecker, elfin woods warbler, Puerto Rican tanager,

and the Puerto Rican bullfinch. It is also home to the Puerto Rican boa, the island’s

largest native snake species, which is under protected status. Much larger numbers

of invertebrates are present, and some are yet to be discovered.

The Forest Service manages the EYNF/Luquillo Experimental Forest under a

policy of multiple use that calls for the integration of the various desirable uses of

the area for the greatest general good. Both social and economic returns are considered. Areas within the forest are dedicated primarily to what is considered their

best uses, but may also be used for other purposes that do not unduly interfere with

the primary use.

The principal objective of management is to make these forest lands as productive as possible and to demonstrate the results. About 6070 hectares (15,000 acres)

of the forest are capable of timber production. This area is being managed so that

the yield will not only be sustained in the future, but will increase through forest

improvement. Part of this area is set aside for experimental investigations to determine the best techniques of timber management. Elsewhere, inferior trees are

removed and are being replaced by more productive young growth. Trees with poor

form are cut or poisoned, and the mature trees of better formed species are marked

for sale by forest officers. Sales are made to local operators, and the timber is 

harvested according to sound forest practices. The trees are cut and the logs are

removed in a manner favorable to the growth of future timber crops, as well as the

preservation of soil, water, and other values. Twenty-five percent of the revenues

from the sale of timber, forest products, and land uses is returned to the local 

government for roads and schools.

Three-fourths of all the virgin timber that remains in the Puerto Rican forests,

which once covered the entire island, is included in the Luquillo Experimental

Forest. An area of approximately 809 hectares (2,000 acres), known as the Baño 

de Oro Natural Area, has been permanently set aside by the Chief of the Forest

Service to preserve in virgin condition the four types of forest of these mountains.

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1

See appendix 1 for Common Latin names.
This area is to be used only for scientific studies. No trees are ever cut, nor is the

area to be traversed by a road or trail.

Under the program of development followed by the Forest Service in administering the forest, preserving wildlife values is important. The forest has been established as a commonwealth bird refuge to preserve the Puerto Rican parrot and the

other birds endemic to the island almost exterminated as a result of uncontrolled

hunting and deforestation.

The headwaters of eight major rivers rise in the forest and provide water for

domestic purposes and hydroelectric power for the people of eastern Puerto Rico.

Mismanagement of the vegetation on steep slopes within the forest might endanger

some of the island’s best sources of water by causing floods and accelerated soil

erosion. Critical areas such as peaks, ridges, and steep slopes, which cover about

1214 hectares (3,000 acres) of the forest, have been closed to timber cutting and

other uses so the natural vegetation may continue to protect the soil and retard the

runoff of water. The water that flows out of the forest in streams and underground

watercourses is relatively free of sediment.

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Figure 87—Map of the El Yunque National Forest/Luquillo Experimental 

Forest.
Through the years, more lands were purchased, especially in lower elevations

surrounding the original inholdings, and today the forest covers 11 200 hectares

(28,000 acres) (fig. 87). Its official name is the El Yunque National Forest/Luquillo

Experimental Forest, so designated in 1956 to address research issues. It is the 

only forest in the Nation with this special designation. In October 1976, the United

Nations Educational, Scientific and Cultural Organization (UNESCO) designated it

as part of the Man and the Biosphere International Network of Special Reserves.

This special designation was given in recognition of its unique species diversity,

long history of scientific studies, and its special ecological attributes. The forest is

said to have the longest history of study of all tropical forests in the world. Its special protected status assures that it will be there to promote sustainable intergenerational conservation efforts and to provide a standard against which the effect of

human impact on the environment can be measured. This forest is an active training site for forest managers and research scientists from around the world. In addition, it is easily accessible by the general public, and today, about half a million

visitors from all over the world visit the forest yearly (fig. 88). In recognition of its

special role in public education, the USDA Forest Service opened a state-of-the-art

forest education center, El Portal, in 1997. This “gateway” facility provides a variety of rain forest education exhibits with staff available to answer specific questions, providing forest maps and other literature to the visitor (fig. 89).

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Figure 88—Learning in a natural setting is the basis for ecotourism. 

G. Miller
There are four distinctive forest types in the EYNF: the tabonuco, sierra palm,

palo colorado, and elfin forest. Each of these has been described in detail in the

forest zone section of this document, along with tree species profiles and special

plant groups typical of the forest types.

One of the special features of this forest is that it is relatively easy to access 

by the public. It is located within a couple of hours of driving for the island’s 3.8

million inhabitants and the countless tourists that visit the island each year. San

Juan is only 35 kilometers (25 miles) west of the forest. As part of the USDA

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G. Miller

Figure 89—View of the entryway to El Portal Visitors Center in the El Yunque National

Forest.
Forest Service’s mission of providing multiple use, the forest makes available a

variety of recreational opportunities. There are 13 trails easily accessed by the public varying in hiking length from 15 minutes to 4 hours or more—one-way. There

are four observation towers available for scenic vistas at Yokahú, Mount Britton, 

El Yunque, and Los Picachos. Primitive camping is available. Most users of the

forest are involved with enjoyment of beautiful scenery and waterfalls, its wide

variety of unique plants and animals, and the opportunity to enjoy picnic lunches 

in the cool mountain breezes. Covered pavilions, water, and restroom facilities are

available.

The International Institute of Tropical Forestry (institute) is also located 

in Puerto Rico. In 1928 the U.S. Congress authorized the establishment of a forest

experiment station in the tropical possessions of the United States in the West

Indies. The experiment station was established in 1939, in Río Piedras, Puerto

Rico. Much of their early efforts were centered on repairing damaged watersheds

and improving forestry options so that more valuable and useful species would

replace inferior timber species on damaged and abandoned lands. Today, the institute is an outgrowth of the original forest experiment station (fig. 90).

The institute now conducts programs in state and private forestry and forestry

research and development, and oversees a variety of international cooperative 

programs. It also provides administrative services to its members. In spite of the

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Figure 90—The International Institute of Tropical Forestry located in Río Piedras, Puerto Rico. 

A.E. Lugo
growth in program initiatives and staff, the institute’s scientists still conduct inventories, select species for reforestation, and develop silvicultural practices for tropical timber trees. Today, however, many new research avenues are being pursued

including economic, social, and environmental benefits of healthy forests, atmospheric pollution, global warming, impacts of tropical deforestation and its effects

on global climate, maintaining suitable habitat for various plant and animal species

such as the endangered Puerto Rican parrot, hurricane effects, landscape ecology,

and disturbance ecology.

The institute is designated an independent region of the USDA Forest Service

and reports directly to the Chief. Its Río Piedras facility covers 2 hectares (5 acres)

and includes a large headquarters/office building, specialized geographic information systems, geopositioning system and chemistry laboratories, a library, seed

bank, machine shops, and other support facilities. The institute published the

Caribbean Forester from 1939 to 1953, and over 1,000 technical papers have 

been written by its research staff. Its library is purported to house the best tropical

forestry collection in the New World. Its technical staff has served throughout the

tropical world as research scientists and consultants to dozens of countries and

international agencies. The institute has an active training program for tropical

foresters, graduate students, and visiting university ecology classes from numerous

countries and states in the United States. It maintains the oldest forest research

plots in the hemisphere dating back to the 1940s and maintains continuous growth

records on over 20,000 trees. In 1988, the National Science Foundation designated

the Luquillo Experimental Forest a Long-term Ecological Research Site. In 1990,

the institute and the Luquillo Experimental Forest received the USDA Forest

Service Stewardship Award for their outstanding contributions to forest conservation.

Administratively, the institute’s director is supervised by the Chief of the U.S.

Forest Service and the institute operates much like a Forest Service region. Today,

the institute has about 65 to 70 employees and an $8 million budget (including

grants and contracts). Thirty countries and 80 environmental/governmental/educational organizations have formal agreements with the institute. The institute, in

combination with the EYNF, is developing ecosystem management initiatives that

will allow people in the tropics to use their forests based on sustainable forestry

practices that are necessary to maintain healthy, productive, and diverse forests in

the new millennium.

For further reading see Lugo and Mastrantonio 1999, Steinkamp et. al 1996,

and Weaver 1994.

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Puerto Rico’s Commonwealth Forests and Nature 

Reserves

Puerto Rico now has 118 natural areas that include federal reserves, commonwealth

forests and refuges, and nongovernment conservation areas. They range in size

from the 11 336-hectare (28,000 acre) El Yunque National Forest in the Luquillo

Mountains, to the commonwealth protected 2-hectare (4.94-acre) mangrove swamp

at Naguabo.

Puerto Rico has 14 commonwealth forests distributed throughout the island

(fig. 91). They serve as functioning forests and are operated under the principles of

multiple-use resource management. All have trail systems, and some have welldeveloped bike trails and camping facilities. They are grouped according to their

geographic position: karst (K), coastal (C), and mountain upland (U). For a complete description of each forest, its soils, climate, wildlife, unique natural areas, and

management issues, see the 1976 Master Plan for the Commonwealth Forests of

Puerto Rico of the Department of Natural Resources, San Juan, Puerto Rico. All

forests are open 7 days a week from 7:00 a.m. to sunset unless posted otherwise.

Table 28 provides a description of each forest’s location, as well as, size, habitats,

and facilities.

Puerto Rico also has regional nature reserves, which serve to protect habitat,

and the animals and plants located within and near them. Table 29 provides information about the nature reserves.

As described in the section on environmental organizations in Puerto Rico that

follows, there are a variety of nongovernmental organizations (NGO) working at

the local and commonwealth level in preservation and conservation of species and

critical ecological habitats. The Puerto Rican Conservation Trust is one of the

NGOs operating in Puerto Rico. The trust manages 14 high-profile cultural, environmental, and ecologically significant properties encompassing more than 

5263 hectares of land (13,000 acres) spread throughout Puerto Rico (fig. 92). Their

education programs now reach nearly 150,000 people a year. They offer environmental camps and special education programs in cooperation with the public

schools. Their trust properties include:

➢ Las Cabezas de San Juan Nature Reserve (Fajardo) is exceptional 

for its diversity of marine and terrestrial habitats, with full educational

services, programs, and transportation–128 hectares (316 acres).

➢ Hacienda Buena Vista (Ponce) is a fully restored 19th-century farm 

and coffee plantation with period canal and water-based technology, 

and functioning coffee and corn mill–218 hectares (496 acres).

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Figure 91—

Public forests and forest lands of Puerto Rico. The public forests (solid black) are 14 com

monwealth forests (bosques estatales) and the El Yunque National

Forest or Luquillo Experimental Forest (federal). Shaded areas are forest lands adjacent to public forests. From

Little et al. 1974.
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Table 28—Visiting the commonwealth forests of Puerto Rico 

Forest name and location Phone Size Habitats

Central office of forest (787) 724-3724 Hectares (acres) Island-wide coordination of all forest 

Reserves reserves

San Juan, PR

Piñonesa (C) (787) 791-7750 613 Coastal beach (sandy and rocky), mangrove 

Route 187 (behind the San (1,513) swamps, dry scrub woodland 

Juan International Airport) Features newly constructed bike trail 

along the coast to Loiza throughout the forest’s habitats.

Lots of sandy beach access, 46 bird species

Ceiba (C) (787) 852-4440 143 Coastal beach thicket, salt flats, mangrove 

Located between Fajardo (352) swamps, turtle grass beds, manatee habitat

and the town of Ceiba 

along the coast

Aguirre (C) (787) 864-0105 968 Mangrove swamps, tidal flats, bird rookeries, 

Off Route 3 east of Salinas (2,390) marine research area, manatee habitat, 60 bird 

species

Guánica (C)

Route 116 to Route 334 (787) 821-5706 3879 Dry forest habitat known for its high bird 

and follow signs (9,582) diversity 

Beaches, mangroves, and visitor center (center 

is closed Mondays) 

Twelve hiking trails are available, maps can be 

obtained at the education center

Boquerón (C) (787) 851-7260 801 Mudflats, salinas, mangrove swamps, and 

Forest office west of (1,979) interpretive trails. Very good for coastal

Boquerón off Route 101 birds (50 species) and fish (58 species)

Carite (U) (787) 747-4545 2616 Features pine plantation and camping 

Route 184, (787) 864-8903 (6,460) opportunities (16 sites), 30 bird species

southeast of Caguas

Guilarte (U) (787) 829-5767 1415 Features a hiking trail to 1204 meter 

Located southwest of (787) 852-4440 (3,495) (3,940 feet), Guilarte Peak, and visitors center 

Adjuntas, south on Route Five rental cabins are available

131 or Route 518

Toro Negro (U) (787) 867-3040 2727 Tallest peaks in Puerto Rico (Cerro de Punta

Route 143 at km 31.8, (787) 844-4660 (6,737) and Cerro La Rosa), 7 campsites, hiking trails

east of Route 149

Susúa (U) (787) 724-3724 1312 Mountain bike trail, good view of carbonate 

Northeast of Sabana Grande (787) 833-3700 (3,241) formations, 40 campsites

on Route 368 at km 2.1

Maricao (U) (787) 724-3724 4151 Observation tower, fish hatchery and hiking

North of Sabana Grande (10,251) trails, 26 bird species (11 endemics)

on Route 120

Vega Alta (K) (787) 833-2240 447 Caves, sinkholes, and highly variable soils

East of Vega Alta on (1,105)

Route 676 at km 1.5
➢ Phosphorescent Bay and mangrove swamps (La Parguera) protects 

the mangrove swamps surrounding the world-famous bay–327 hectares

(807 acres).

➢ Sotomayor Nature Reserve (Caguas) preserves mountain tract of virgin

forest at the headwaters of the Turabo River–26 hectares (63 acres).

➢ Río Portugues Forest (Adjuntas) is a conservation easement protecting

sierra palm forest on headwaters of the Portugues River–17 hectares 

(42 acres).

➢ San Cristobal Canyon Reserve (Barranquitas) protects the northern 

rim of a volcanic rift in the Cordillera Central with ravines over 229 

meters (750 feet) deep–405 hectares (1,000 acres).

➢ Punta Guaniquilla Reserve (Cabo Rojo) protects arid promontories 

overlooking the sea, dry forest areas, two lagoons, caves, mangroves,

sculptured limestone rocks, and habitat for the endangered West Indian

whistling duck. This is an important wintering and migratory bird 

sanctuary–157 hectares (388 acres).

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Guide To The Ecological Systems Of Puerto Rico

Table 28—Visiting the commonwealth forests of Puerto Rico (continued) 

Forest name and location Phone Size Habitats

Guajataca (K)

Route 446 south of Route 2 (787) 872-1045 926 Largest hiking trail system in the forest reserves 

(787) 890-4050 (2,286) (44 kilometers/26 miles), observation tower, 

bird watching (45 species) and good view of 

karst topography. Camping (10 sites) available 

Forest maps available at the north entrance

Rio Abajo (K) (787) 880-6557 2270 Karst cave systems, hiking trails, large 

South of Arecibo on Route (787) 878-7279 (5,607) camp sites

10 at km 70.3, then west 

on 621 to km 4.4

Cambalache (K) (787) 881-1004 373 Camping (12 sites), hiking trails (13 kilometers

West of Barceloneta on (787) 878-7279 (922) /8 miles), mountain bike trails, 45 bird species

Route 682 at km 6.6

Note: Camping areas charge $4 per person per night. The cabins at Guilarte Forest rent for $20 per night.

a One of the newest additions to the commonwealth forest’s recreation system is the recent opening of the $7 million boardwalk and bike 

trail system added to the Piñones Forest. Not only is this an important local recreation and ecotourist destination, but it guarantees the

protection of important coastal wetlands. The new facilities offer opportunities for leisurely coastal walks and up to 7 miles (one way) of

biking opportunities. It starts at Boca de Cangrejos, just up the beach from the El San Juan Hotel. This area has excellent beach front for

swimming. The new path system will include 31 kiosks for bike and auto parking, as well as an information center describing the habitats

and recreation opportunities in the area. This boardwalk has produced new opportunities for ecotourist companies to offer bike, nature,

and sea kayak trips.
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General Technical Report IITF-35

Table 29—Nature reserves of Puerto Rico

Reserves name 

and address Phone Habitats

Las Cabezasaa de San Juan (787) 722-5882 128 hectares (316 acres) of coastal headlands, 

Nature Reserve (787) 860-2560 128 hectares (316 acres) of coastal headlands, 

Highway 3, then left to - (on weekends) mangroves with boardwalk, lighthouse, beaches, 

Fajardo on Route 194, left Open Friday through Sunday cactus populations, bird watching, hiking trails, 

at Monte Brisas Shopping by reservation only. English and new visitor center. Group transportation 

Center, then right at next tours 2:00 p.m takes you through the preserve

light, left onto Route 987, Admission = $5/adults; 

follow signs to entrance $2/children

Group tours available on 

Wednesdays and Thursdays

Humacao Wildlife Refuge 1215 hectares (3,000 acres) of former cane 

Off Route 3 east of fields and cattle pasture that is undergoing 

Humacao succession and reclamation

Caja de Muertos Uninhabited island off the coast at Ponce, with hiking

Island Nature Reserve trails, lighthouse, dry scrub, and underwater park 

Public ferries leave from with good reefs 

municipal dock at Ponce (Take your own shade and water supply)

on the La Guancha 

boardwalk early in the 

morning and return late in 

the afternoon

Boquerón Forest Bird (787) 851-4795 Walking trails and boardwalks through mangrove 

Refuge swamps and lagoon

Route 301 at km 1.1 east Fishing and hunting are seasonally permitted on this 

of Boqueron 182-hectare (450-acre) preserve

Lago Lucchetti Wildlife (787) 844-4660 Campsites, recreation area, boat ramp

Refuge

Near Yauco, Route 128 to 

refuge entrance at km 12.3

Lake Tortuguero Reserve (See the wetlands section Freshwater wetlands with a variety of palustrine 

East of Manati on Route 2, for details on this preserve) species and habitats, contains small population 

north on Route 687 of caimans

Other nature reserves are also located at the Lagoon Reserve at Joyuda in Cabo Rojo, Río Espiritu Santo in Río Grande, Wetlands 

Reserve at Caño Tiburones in Arecibo, the Coral Reef Reserve at Guayama. a Las Cabezas de San Juan Reserve has been studied ecologically and taxonomically and a full description of its plant and animal 

communities has been published in Weaver et al. 1999a, 1999b.
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Guide To The Ecological Systems Of Puerto Rico

Figure 92—

Puerto Rico Conservation Trust properties.
➢ Hacienda La Esperanza (Manatí) protects farmlands on alluvial flood

plain bordering the Atlantic Ocean, with coves, karst, and cemented 

dunes. It also features an old sugar mill and manor house–922 hectares

(2,278 acres).

➢ Inés María Mendoza Reserve of Muñoz Marín (Yabucoa) protects 

scenic tree-lined sandstone cliffs and habitat for the endangered grasshopper sparrow–117 hectares (290 acres).

➢ Punta Ballena Reserve (Guánica) is an extension of the Guánica

Forest–68 hectares (167 acres).

➢ Pterocarpus Forest Reserve (Humacao and Dorado) protects freshwater

marsh and bloodroot swamps–294 hectares (727 acres).

➢ Montes Oscuros (Salinas)—safeguards a large area of rainshadow 

mountain landscape in cooperation with the National Guard at Camp

Santiago–2,834 hectares (7,000 acres).

The conservation trust’s headquarters are in the beautifully restored Giralt 

House in Old San Juan, located at 155 Tetuán Street. There are various trust property exhibits on display, as well as the home that was built in the 1700s. Hours are

Tuesday through Saturday, 10:00 a.m. to 4:00 p.m.; (787) 722-5834.

For further reading see Little et. al 1974.

Caribbean Islands National Wildlife Refuge

National wildlife refuges (NWR) in the United States, its territories, and the 

Commonwealth of Puerto Rico are administered by the U.S. Fish and Wildlife

Service (FWS) of the Department of the Interior. There are over 500 refuges in the

United States and the Caribbean. Some of the most recently established refuges are

the seven refuges in Puerto Rico (4) and the U.S. Virgin Islands (3). These refuges

constitute the Caribbean Islands National Wildlife Refuge System (CINWR). They

provide visitors with an opportunity to observe a variety of wildlife species, and

the plant communities that support them, in addition to archeological sites. Two of

Puerto Rico’s NWRs are located on the nearby islands of Desecheo and Culebra.

The two mainland refuges are in the southwest corner of the island at Cabo Rojo

(see app. 2) and Laguna Cartagena (fig. 93). They are located within 7.5 kilometers

(4.5 miles) of each other off Puerto Rico Routes 301 and 305. These two refuges

are described below. More detailed information describing the other five can be

obtained by contacting the CINWR.

The original 237-hectare (587-acre) upland tract was acquired in 1974 and

developed into the Cabo Rojo National Wildlife Refuge (CRNWR) in 1978. The

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General Technical Report IITF-35
305

land had been used for nearly 200 years for cattle grazing and agriculture. The

refuge lies within the subtropical dry forest life zone but has little of its original

vegetation owing to long periods of overgrazing. Much of the vegetation cover

today is composed of introduced alien species of grass, forbs, and woody plants.

They do not provide optimal nesting habitat or food materials to the animals of the

refuge. Restoration management programs are in place to promote regrowth of

native herbaceous plant species. Native woody plants are being planted to return

much of the refuge land to its original hardwood status typical of the dry forest

originally present, including the endangered Stahlia monosperma (Tul.) Urban.

The primary wildlife serviced by this refuge are native and migratory

Neotropical bird species. This is a habitat used by many species migrating between

the North and South America mainlands. Species you can expect to see are:

Winter migrants Native species

➢ Prairie warbler (Dendroica ➢ Puerto Rican flycatcher 

discolor) (Myiarchus antillarum)

➢ Northern parula warbler (Parula ➢ Puerto Rican vireo (Vireo latimeri)

americana) ➢ Puerto Rican tody (Todus mexi 

canus)

Guide To The Ecological Systems Of Puerto Rico

Figure 93—Location of national wildlife refuges in southwest Puerto Rico.
➢ Cape May warbler (Dendroica ➢ Rock dove (Columba livia)

tigrina) ➢ Adelaide’s warbler (Dendroica

adelaidae)

➢ Gray kingbird (Tyrannus 

dominicensis)

➢ Caribbean elaenia (Elaenia 

martinica)

➢ Yellow-shouldered blackbird 

(Agelaius xanthomus)

(endangered species)

➢ Turkey vulture (Cathartes aura)

➢ Bananaquit (Coereba flaveola)

A complete list of refuge bird species is available from the CRNWR.

The only native land mammal species present are bats. Two alien mammals

may be seen as you walk the 23 kilometers (14 miles) of trails: Indian mongoose

and African patas monkeys. Nearby marine waters of the refuge may contain manatees and whales. Sea turtles may use the beaches for nesting.

The 526-hectare (1,300-acre) Cabo Rojo Salt Flats were purchased from private owners in 1998 through the Trust for Public Lands, The Natural Resources

Conservation Service, and the Puerto Rico Conservation Foundation. These lands

were incorporated into the refuge. It is a system of saline lagoons, salt flats, and

mangrove swamps adjacent to the upland section and constitute the most important

stopover site for migratory shorebirds known in the Caribbean region. Species 

likely to be seen in this estuarine complex are:

➢ Brown pelican (Pelicanus ➢ Ruddy turnstone (Arenaria 

occidentalis) interpres)

➢ Magnificent frigatebird (Fregata ➢ Lesser yellowlegs (Tringa 

magnificens) flavipes)

➢ Great blue heron (Ardea ➢ Greater yellowlegs (Tringa 

herodias) melanoleuca)

➢ Green-backed heron (Butorides ➢ Least sandpiper (Calidris 

virescens minutilla)

➢ Cattle egret (Bublulcus ibis) ➢ Semipalmated sandpiper (Calidris 

pusilla)

➢ Snowy egret (Egretta thula) ➢ Royal tern (Sterna maxima)

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General Technical Report IITF-35
➢ Yellow-crowned night heron ➢ Cave swallow (Petrochelidon

(Nyctanassa violacea) fulva)

➢ Simipalmated plover (Charadrius ➢ Northern mockingbird (Mimus

semipalmatus) polyglottos)

➢ Killdeer (Charadrius vociferous) ➢ Yellow warbler (Dendroica 

petechia)

➢ Black-necked stilt (Himantopus

mexicanus)

The Laguna Cartagena National Wildlife Refuge (LCNWR) is 419 hectares 

(1,036 acres) in the Lajas Valley and is a remnant of a former large lake and associated palustrine wetlands (see app. 2). It is still one of the most important freshwater

habitats for migratory waterfowl and wading birds in Puerto Rico and the only significant freshwater marsh in southwestern Puerto Rico. Nearly half of the birds

recorded in Puerto Rico have been found in the lagoon and adjacent nearby hills

(164 species). Most of this extensive tract was heavily altered by sugarcane growers

and cattle farmers. Much of the lagoon is overgrown with Typha spp. (cattails),

Eichhornia crassipes (Mart.) Solms-Laub (water hyacinth), and Pistia stratiotes L.

(water lettuce). Sediments, fertilizers, and pesticides have run into the lagoon for

decades. Water birds have restricted use for feeding and nesting owing to the heavy

emergent vegetation. The Puerto Rico Land Administration leased the land in 1989

to the U.S. Fish and Wildlife Service who rehabilitated some of the lagoon for resident and migratory waterfowl. Mitigation activities around the lagoon are converting

former grazing and sugarcane lands to forested habitats for resident native species.

Birds typical of this habitat are:

➢ Belted kingfisher (Ceryle alcyon) ➢ Puerto Rican flycatcher 

➢ Great blue heron (Ardea herodias) (Myiarchus antillarum)

➢ Herons (several species) ➢ Caribbean elaenia (Elaenia 

➢ Smooth-billed ani (Crotophaga ani) martinica)

➢ Yellow-shouldered blackbird ➢ Troupial (Icterus icterus)

(Agelaius xanthomus) (endangered ➢ Pin-tailed whydah (Vidua macroura)

species) ➢ Common snipe (Gallinago 

➢ Bananaquit (Coereba flaveola) gallinago)

➢ Lesser yellowlegs (Tringa flavipes)

For further reading see U.S. Department of the Interior, Fish and Wildlife 

Service 1997.

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Guide To The Ecological Systems Of Puerto Rico
Other Environmental Organizations

As was the case throughout much of the world, Puerto Rico had little in the way

of publicly organized environmental interests through the mid 1960s. Much of the

island had major air and water pollution problems. Solid wastes littered the countryside, and municipal wastes were frequently dumped over beautiful seaside cliffs,

set on fire, and burned continuously, resulting in a regional odor that announced the

dump’s position miles away. Many beaches were littered with beverage containers.

The famous Phosphorescent Bay’s bottom was a depository for wastes thrown

overboard from private boats that would anchor there. Beaches throughout the

island were subject to exposure to municipal sewage outfalls via long shore drift

because secondary sewerage treatment was basically nonexistent at the time. In

light of these problems, on January 30, 1966, a group of 59 professors and intellectuals took out a full-page advertisement in the San Juan Star newspaper calling

the attention of all Puerto Ricans to the plight of the island’s environment. 

This was a call to action for environmental cleanup and conservation of natural

resources. It marked the beginning of organized environmentalism in Puerto Rico.

With the beginning of the environmental movement in the United States and punctuated by the first Earth Day on April 22, 1970, interest in the environment

emerged throughout Puerto Rico as well. Today, as in most developed countries,

Puerto Rico’s environmental issues are front-page news. In the last three decades,

numerous commonwealth agencies have been developed to address and control

most environmental problems. At the federal level, all of the national agencies 

have regional offices or personnel specially designated to deal with environmental 

problems specific to Puerto Rico and the Virgin Islands. For instance the U.S.

Environmental Protection Agency (EPA) includes these islands in their New YorkNew Jersey Region 2.

Although the conservation movement in Puerto Rico started as a general 

concern of intellectuals over the levels of pollution in soil, air, and water, today,

the movement is based on grassroots community action seeking protection from

environmental problems that touch their daily lives—for example, water supply,

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General Technical Report IITF-35
garbage disposal, or flooding of property. Puerto Rico’s growth has been so 

disorganized and the population density is so high that any proposal for further

development projects impacts some sector of society. Because there is a poor tradition of consultation and fair implementation of administrative procedures, new

environmental groups develop continuously, each focused on a particular local

issue that affects people, habitats, or species. As a result, Puerto Rico’s environmental movement is highly fragmented, and the public media contains numerous

daily reports of environmental issues that result in confrontation and conflicts

among various sectors of society. For a review of critical issues facing environmental organizations and the citizens of Puerto Rico, see Lugo (1994). In August

2003, various environmental and health groups met for the first environmental

health summit. Their purpose was to develop methods to support each other and 

to develop strategies and policies effective locally and globally. One of their main

aims was to address the issue of local and global sustainability and to try to reduce

the destruction of Puerto Rico’s natural resources.

In the 1960s, there were only a handful of NGOs actively involved in pollution

control, habitat degradation, recycling, status of native species, environmental 

education, and so forth. As we entered the new millennium, dozens of groups were

dedicated to these issues. Some are watchdog groups that make sure the various

governmental agencies are correctly following the law, others are interested in

acquiring and conserving valuable habitats and species assemblages, and still 

others are dedicated to public education and increasing the general public’s awareness of the plight of the environment. The following list highlights the key environmental organizations in Puerto Rico. The NGO list identifies groups that are active

islandwide. There are numerous other NGOs at work on the local level throughout

the island. A complete list of Puerto Rico’s NGO’s is available from the Puerto

Rican Conservation Foundation (2000).

For further reading see López Feliciano 1999, Lugo 1994, Lugo Lugo 1981,

and the Puerto Rican Conservation Foundation 2000.

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Guide To The Ecological Systems Of Puerto Rico
Acknowledgments

We are grateful to our institutions for supporting the development of this manuscript. The University of North Carolina at Asheville provided an off-campus

scholarly assignment for Gary Miller to initially develop the manuscript during the

spring semester 2001. The USDA Forest Service, International Institute of Tropical

Forestry provided space, the use of their library, office staff, and graphics for this

manuscript. We extend our sincere appreciation to the many scientists who have

conducted the research and provided the wealth of information reflected in this

document. We thank Debra Robbins and Lía Sánchez for typing the various drafts

of the manuscript. Gisel Reyes collaborated with the bibliography. Mildred Alayón

edited the manuscript, and Helen Nunci assisted with the production. The work was

done in cooperation with the University of Puerto Rico.

We are especially grateful to our families who have supported our scientific

efforts and extensive field trips throughout our careers. Special recognition is given

to Dr. Herminio Lugo Lugo who made it possible for us to develop our love of the

tropics and the special ecosystems found there.

Metric and English Equivalents

When you know Multiply by To find

Millimeters 0.0394 Inches

Centimeters .3934 Inches

Meters 3.28 Feet

Kilometers 6214 Miles 

Square meters 10.76 Square feet 

Square kilometers 0.386 Square miles 

Hectares 2.47 Acres 

Liters .264 Gallons

Cubic meters 35.3 Cubic feet 

Cubic meters .000811 Acre-feet 

Milligrams .00003527 Ounces

Grams .03527 Ounces

Kilograms 2.205 Ounces

Metric tons 2204.62 Pounds

Metric tons 1.102 Short tons 

Kilocalories 3.968 British thermal units 

Celsius degrees 1.8 C+32 Fahrenheit degrees 

310

General Technical Report IITF-35
Inches 25.40 Millimeters 

Inches 2.54 Centimeters 

Feet .3048 Meters 

Miles 1.609 Kilometers 

Nautical miles 1.852 Kilometers 

Square feet .0929 Square meters 

Square miles 2.59 Square kilometers 

Acres .405 Hectares 

Gallons 3.78 Liters 

Cubic feet .0283 Cubic meters 

Acre-feet 1233.6 Cubic meters 

Ounces 28.4 Grams 

Pounds .454 Kilograms 

Short tons .907 Metric tons

British thermal units .252 Kilocalories

Fahrenheit degrees (F-32)/8 Celsius degrees 

311

Guide To The Ecological Systems Of Puerto Rico

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Appendix 1: Common and Scientific Names of Plant

and Animal Species

Common name Scientific name

Plants 

African cactus Euphorbia lacteal Haw.

African milkweed tree Calotropis procera (Aiton) W.T. Aiton

African tulip tree Spathodea campanulata Beauv.

Aloe vera Sansevieria spp.

Arana Schoepfia arenaria Britt.

Arrowhead Sagittaria lancifolia L.

Australian pine Casuarina equisetifolia L.

Ausubo Manilkara bidentata (A.DC.) Chev.

Autograph tree (postcard tree) Clusia rosea Jacq.

Avocado Persea Americana Mill.

Ball moss Tillandsia recurvata (L.) L.

Balsa Ochroma pyramidale (Cav.) Urban

Bamboo Bambusa vulgaris (Schrad ex. Wendl.)

Banana Musa paradisiaca L.

Bariaco Trichilia triacantha

Barrio Charcas maiden fern Thelypteris verecunda Proctor

Bayberry Myrica cerifera L.

Baycedar Suriana maritima L.

Beach dropseed Sporobolus virginicus (L.) Kunth.

Beach morning glory Ipomoea pes-caprae (L.) R. Br.

Beach rush Scleria microcarpa Nees

Beach spine Anthacanthus spinosus L.

Begonia Begonia spp.

Bird’s nest fern Asplenium serratum

Bird-of-paradise Strelitzia reginae Banks ex Dryand

Black mangrove Avicennia germinans L.

Bladderwort Utricularia gibba L.

U. obtusa Sw.

Bonzai plant Strumpfia maritime Jacq.

Bougainvillea Bougainvillea spectabilis Willd.

Breadfruit Artocarpus altilis (Parkinson) Fosberg

Broomstraw Andropogon gerardii Vitman

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Common name Scientific name

Plants continued

Brown strap alga Dictyopteris spp.

Buttonwood mangrove Conocarpus erectus L.

Cachimbo Palicourea riparia

Psychotria berteriana

Camasey Miconia prasina

Camasey shrub Miconia impetiolaris

Caña Gorda girdlepod Mitracarpus polycladus Urban

Canonball tree Couroupita guianensis Aubl.

Caparosa Callicarpa ampla Schauer

Carrasco Comocladia glabra (Schultes) Spreng.

Cassava Manihot esculenta Crantz

Cat briar Smilax coriacea Spreng.

Cattail Typha angustifolia L.

Century plant Agave spp.

Cerro de Punta Jayuya Elaphoglossum serpens Maxon & Morton ex 

Maxon

Chase’s threeawn Aristida chaseae A.S. Hitchc.

Chicarrón Comocladia dodonaea (L.) Urban

Chickenwood Dalbergia ecastaphyllum (L.) Taubert

Chocolate tree Theobroma cacao L.

Chupacallos Pleodendron macranthum (Baill.) v. Tiegh.

Cinnamon fern Osmunda cinnamomea

Citrus Citrus spp.

Clubmoss Lycopodium spp.

Cobana negra Stahlia monosperma (Tul.) Urban

Coconut palm Cocos nucifera L.

Coco plum Chrysobalanus icaco L.

Coffee Coffea arabica L.

C. liberica

C. robusta

Coffee colubrine Colubrina arborescens (Mill.) Sarg.

Coffee leaf rust Hemileia vastatrix

Common bamboo Bambusa vulgaris Schrad. ex J.C. Wendl.

Common coleus Coleus blumei

Common philodendron Philodendron oxycardium

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Common name Scientific name

Plants continued

Common roadside ferns Gleichenia bifida

G. pectinata

Coontail Ceratophyllum demersum

Coralline shelf alga Lithothamnion spp.

Coralline watercress alga Halimeda opuntia (L.) Lamouroux

Cordillera maiden fern Thelypteris inabonensis Proctor

Custard apple Annona reticulate L.

Dead man’s fingers Codium decorticatum

Dinoflagellates Gymnodinium spp.

Amphidium spp.

Duckweed Lemna perpusilla Torr.

Eared woodfern Thelypteris deltoidea

Elfin tree fern Cyathea dryopteroides Maxon

Erubia Solanum drymophilum O.E. Schulz

False nettle Boehmeria cylindrical (L.) Swartz

Fiddle-leaf morning glory Ipomoea stolonifera (Cyrillo) Poir.

Figs Ficus spp.

Fire algae Pyrodinium bahamense

Flamboyán Delonix regia (Bojer) Raf.

Florida poison tree Metopium toxiferum (L.) Kang & Urban

Flower fern Nephrolepis multiflora

Fragile-branched coralline Amphiroa fragilissima

alga

Frangipani Plumeria alba L.

P. rubra L.

Giant sedge Rhynchospora gigantean Link

Ginger (wild) Alpinia purpurata (Veill.) Schum.

Ginger (commercial) Zingiber officinale Rosc.

Glassworts Salicornia bigelovii Torrey.

S. perennis Mill.

S. virginica L.

Grape alga Caulerpa racemosa (Fors.) J. Agardh

Grapefruit Citrus paradise Maefayden

Grass Ichnanthus pallens

Green bubble alga Dictyosphaeria cavernosa (Forsskal) Boergesen

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Common name Scientific name

Plants continued

Green feather alga Caulerpa sertularioides

Green filmy fern Hymenophyllum rigidum

Green tube alga Enteromorpha spp.

Guava Inga vera

Guayabota Eugenia borinquensis Britt. Q

Gumbo limbo Bursera simaruba (L.) Sarg.

Gum tree Manilkara zapota (L.) V. Royen

Haircap moss Polytrichum spp.

Hard fan alga Udotea flabellum (Ellis & Solander) Lamouroux

Helecho arbóreo de bosque Cyathea dryopteroides

Heller’s cieneguillo Daphnopsis helleriana (Urban)

Hibiscus Hibiscus rosa-sinensis L.

Higo chumbo Harrisia portoricensis

Higuero de sierra Crescentia portoricensis

Higuillo de hoja menuda Piper aduncum L.

Horsetails Equisetum spp.

Insectivorous sundew Drosera intermedia Hayne

Jamaican broom Chamaecrista glandulosa var. mirabilis (Pollard) 

Irwin & Barneby

Jamaica walnut Juglans jamaicensis C. DC.

Jerusalem thorn Parkinsonia aculeate L.

Kapok Ceiba pentandra (L.) Gaertn.

Ladies tresses orchid Spiranthes spp.

Large philodendron Philodendron giganteum Schott

Large pipe cactus Cephalocereus royenii (L.) Byles & Rowley

Laurel magnolia Magnolia splendens Urban

Lemon tree Citrus limon (L.) Burmf. F.

Lettuce leaf alga Ulva lactuca L.

Lignum vitae Guaiacum officinale L.

Lime tree Citrus aurantifolia (Christm.) Swingle

Lipstick tree Bixa orellana L.

Liverworts Marchantia spp.

Lobster claw Heliconia caribaea Lam.

Luquillo Mountain babyboot Lepanthes eltoroensis Stimson

orchid

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General Technical Report IITF-35
Common name Scientific name

Plants continued

Luquillo Mountain stopper Eugenia haematocarpa Alain

Magnolia Magnolia splendens Urban

Maidenhair fern Adiantum latifolium Lam.

Manatee grass Syringodium filiforme Kuetz.

Mango Mangifera indica L.

Mangrove fern Acrostichum aureum L.

Marijuana Cannabis sativa L.

Matabuey Goetzea elegans Wydler

Matchwood Didymopanax morototoni (Aubl.) Dcne. & 

Planch

Mat fern Gleichenia bifida (Willd.) Spreng.

Maxwell’s girdlepod Mitracarpus maxwelliae Britton & P. Wilson

Mermaid’s fan alga Udotea conglutinata

Mermaid’s wineglass alga Acetabularia crenulata Lam.

Mesquite Prosopis juliflora (Sw.) DC.

Mid-rib seagrass Halophila baillonis Aschers. Ex Dickie

Molasses grass Melinis minutifolia Beauv.

Monte Guilarte hollyfern Polystichum calderonense Proctor

Motillo Sloanea berteriana Choisy ex DC.

Mountain fern Dennstaedtia bipinnata (Cav.) Maxon

Nemoca Ocotea spathulata Mez.

Nigua Cornutia obovata Urban

[No common name] Myrica paganii Krug & Urban

[No common name] Vernonia proctorii L.E. Urbasch

[No common name] Tectaria estremerana Proctor & Evans

Nutmeg Myristica fragrans Houtt.

Orange tree Citrus sinensis (L.) Osbeck

Paddle-blade alga Avrainvillea longicaulis (Kuetzing) Murria & 

Boodle

Palma de manaca Calyptronoma rivales (O.F. Cook) Bailey

Palo colorado Cyrilla racemiflora L.

Ternstroemia luquillensis Krug & Urban

Palo de jazmín Styrax portoricensis Krug & Urban

Palo de nigua Cornutia obovata Urban

Palo de ramón Banara vanderbiltii Urban

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Guide To The Ecological Systems Of Puerto Rico
Common name Scientific name

Plants continued

Palo de rosa Ottoschulzia rhodoxylon (Urban) Urban

Papaya Carica papaya L.

Parrotbeak orchid Octadesmia montana (Swartz) Bentham

Peat moss Sphagnum

Pelos del diablo Aristida portoricensis Pilger

Pepper Piper aduncum L.

Philodendron Monstera spp.

Pineapple Ananas comosus (L.) Merr.

Pincho palo de rosa Ottoschulzia rhodoxylon (Urban) Urban

Pink blush alga Wrangelia argus

Pink calcareous alga Goniolithon strictum (Foslie) Setchell & Mason

Pipe organ cactus Lemaireocereus hystrix (Haw.) Britton & Rose

Pitcairn’s bromeliad Pitcairnia spp.

Plantain Plantago major L.

Poison carrasco Comocladia glabra (J.A. Schultes) Spreng.

Poison chicarrón Comocladia dodonaea (L.) Urban

Polysiphonia Polysiphonia spp.

Pond apple Annona glabra L.

Pondweed Potamogeton nodosus Poir.

Proctor’s staggerbush Lyonia truncate Urban var. proctorii Judd

Prickly pear cactus Opuntia dillenii (Ker-Gawl.) Haw.

Puerto Rican century plan Furcraea tuberose (P. Mill.) Ait. f.

Puerto Rican lobelia Lobelia portoricensis (Vatke) Urban

Puerto Rico applecactus Harrisia portoricensis Britt.

Puerto Rico helmet orchid Cranichis ricartii Ackerman

Puerto Rico maidenhair Adiantum vivesii Proctor

Puerto Rico maiden fern Thelypteris yaucoensis Proctor

Puerto Rico manac Calyptronoma rivales (O.F.Cook) Bailey

Red banded alga Ceramium spp.

Red branched alga Gracilaria spp.

Red brittle alga Acanthophora spicifera (Vahl) Boergesen

Red butterfly orchid Psychilis kraenzlinii (Bello) Sauleda

Red coralline alga Lithothamnion spp.

Red filament alga Spyridia filamentosa

Red lace alga Dictyurus occidentalis

350

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Common name Scientific name

Plants continued

Red leaf bromeliad Vriesea sintenisii (Baker) L.B. Sm. & Pittendr.

Red mangrove Rhizophora mangle L.

Red tuft alga Chondria spp.

Reed Phragmites australis (Cav.) Trin. ex stend.

Roble de sierra Tabebuia rigida Urban

Rose tuft alga Ceramium nitens

Royal palm Roystonea regia

Salwort Batis maritime L.

Sandspur Cenchrus echinatus L.

Santa María Calophyllum brasiliense

Sargassum Sargassum natans

Sawgrass Cladium jamaicense Crantz

Screw pine Pandanus odoratissimus Parkinson ex Zucc.

Sea bean Canavalia maritima Thouars

Sea fern Bryopsis pennata (Harvey) Collins & Hervey

Sea grapes Coccoloba uvifera (L.) L.

Sea grass Spartina patens (Ait.) Muhl.

Sea ox-eye Borrichia arborescens (L.) DC.

Sea paspalum Paspalum vaginatum (Sw.)

Sea pearls Valonia ventricosa J. Agardh

Sea purselane Sesuvium portulacastrum (L.) L.

Sea rocket Cakile lanceolata (Willd.) O.E. Schultz

Sea vine Halophila decipiens Ostenf.

Sebucan Leptocereus grantianus Britt.

Sensitive plant Mimosa pudica L.

Serpentine manjack Cordia bellonis Urban

Shaving brush alga Penicillus capitatus Lamarck

Shield fern Dryopteris spp.

Shoal grass Halodule wrightii Aschers.

Shortleaf fig Ficus citrifolia P. Mill.

Sierra palm Prestoea montana (Graham) Nichols.

Sintensis’ holly Ilex sintenisii (Urban) Britton

Six-leaved seagrass Halophila engelmannii Aschers.

Small spiny tree fern Cyathea pubescens sensu Maxon, non Mett. ex 

Kuhn

351

Guide To The Ecological Systems Of Puerto Rico
Common name Scientific name

Plants continued

Snake plant Sansevieria spp.

Soft fan alga Avrainvillea nigricans Decaisne

Soil fungus Aspergillus spp.

Southern cattail Typha domingensis Pers.

Spanish moss Tillandsia usneoides (L.) L.

Spike moss Selaginella spp.

Spiny tree fern Nephelea portoricensis (Spreng. ex Kuhn) R. 

Tryon

Staghorn fern Platycerium bifurcatum (Cav.) C. Christens.

Stalked lettuce alga Halimeda tuna

Strap alga Dictyota divaricata

Strap fern Polypodium crassifolium L.

St. Thomas prickly ash Zanthoxylum thomasianum (Krug & Urban) 

Krug & Urban ex P. Wilson

Sugarcane Saccharum officinarum L.

Sundew Drosera capillaries Poir.

Swamp bloodwood Pterocarpus officinalis Jacq.

Swamp water fern Blechnum indicum Burm. f.

Sweet acacia Acacia farnesiana (L.) Willd.

Tabonuco Dacryodes excelsa Vahl

Tank epiphyte Guzmania berteroniana (Schult. & Schult. f.) 

Mez

Tan petticoat alga Padina sanctae-crucis Boergesen

Te Ilex cookii Britton & P. Wilson

Three finger leaf alga Halimeda incrassata (Ellis) Lamouroux

Thomas’ lidflower Calyptranthes thomasiana O. Berg.

Tobacco Nicotiana tabacum L.

Touch-me-nots Impatiens sultana Hook. f.

Tree cactus Opuntia rubescens Salm-Dyck ex DC.

Tree fern Cyathea arborea (L.) Sm.

Tropical lilythorn Catesbaea melanocarpa Krug & Urban

Trumpet tree Cecropia schreberiana Miq.

Turf alga Cladophoropsis spp.

Turk’s cap cactus Melocactus intortus (P. Mill.) Urban

Turtlefat Auerodendron pauciflorum Alain

352

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Common name Scientific name

Plants continued

Turtle grass Thalassia testudinum Banks & Solana. ex 

Koenig

Ucar Bucida buceras L.

Uvillo Eugenia haematocarpa Alain

Vahl’s box Buxus vali Baill.

Vanderbilt’s palo de ramón Banara vanderbiltii Krug & Urban

Vanilla Vanilla planifolia G. Jackson

Vaucheria Vaucheria spp.

Water fern Azolla caroliniana Willd.

Water hyacinth Eichhornia crassipes (Mart.) Solms

Water hydrilla Hydrilla verticillata (L.f.) Royle

Water lettuce Pistia stratiotes L.

Water naiad Najas marina L.

Wet Indian mahogany Swietenia mahagoni (L.) Jacq.

West Indian walnut Juglans jamaicensis C. DC.

Wheeler’s peperomia Peperomia wheeleri Britt.

White albizia Albizia procera (Roxb.) Benth.

White cedar Tabebuia heterophylla (DC.) Britt.

White mangrove Laguncularia racemosa (L.) Gaertn. f.

White water lily Nymphaea odorata Ait.

Widgeon grass Ruppia maritime L.

Wild olive Buchenavia capitata Vahl

Wiskfern Psilotum nudum (L.) Beauv.

Woodbury’s stopper Eugenia woodburyana Alain

Y-branched alga Dictyota divaricata Lamouroux

Yerba maricao de cueva Gesneria pauciflora Urban

Yew leaf alga Caulerpa mexicana Kuetzing

Animals

Amphibians 

Bullfrog Rana catesbeiana

Coqui Eleutherodactylus coqui

Golden coqui Elecutherodactylus jasperi

Marine toad Bufo marinus

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Amphibians continued

Puerto Rican crested toad Peltophryne lemur

Puerto Rican rock frog Eleutherodactylus cooki

Anemones 

Eyeball anemone Zoanthus ocellaris

Green colonial anemone Zoanthus sociatus

Purple anemone Condylactis gigantea

Ringed anemone Bartholomea annulata

Sea anemone Bartholomea spp.

Sun anemone Stoichactis helianthus

Birds

Adelaide’s warbler Dendroica adelaidae

American widgeon Mareca

Bananaquit Coereba flaveola

Beaded periwinkle Tectarius muricatus

Belted kingfisher Ceryle alcyon

Black-necked stilt Himantopus mexicanus

Bluejay Cyanocitta cristata

Blue-winged teal Anas discors

Broad-winged hawk Buteo platypterus brunnescens

Brown pelican Pelecanus occidentalis

Cape May warbler Dendroica tigrina

Cardinal Richmondena cardinalis

Caribbean elaenia Elaenia martinica

Cattle egret Bubulcus ibis

Cave swallow Petrocchelidon fulva

Common snipe Gallinaza gallinaza

Elfin woods warbler Dendroica angelae

Gray kingbird Tyrannus dominicensis

Great blue heron Ardea herodias

Greater yellowlegs Tringa melanoleuca

Green-backed heron Butorides virescens

Green mango hummingbird Anthracothorax viridus

Killdeer Charadrius vociferous

Least sandpiper Calidris minutilla

Lesser yellowlegs Tringa flavipes

Magnificent frigate bird Fregata magnificens

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Birds continued

Mallard Anas platyrhynchos

Northern mockingbird Mimus polyglottos

Northern parula warbler Parula Americana

Partridge Arborophila spp.

Pearly-eyed thrasher Margarops fuscatus

Peregrine falcon Falco peregrinus tundris

Pintail Anas acuta macroura

Pin-tailed whydah Vidua macroura

Piping plover Charadrius melodus

Prairie warbler Dendroica discolor

Puerto Rican bullfinch Loxigilla portoricensi

Puerto Rican emerald Chlorostilbon maugaeus

hummingbird

Puerto Rican hummingbird Anthracothorax dominicus

Puerto Rican flycatcher Myiarchus antillarum

Puerto Rican nightjar or Caprimulgus noctitherus

whip-poor-will

Puerto Rican parrot Amazona vittata vitatta

Puerto Rican plain pigeon Columba inornata wetmorei

Puerto Rican tanager Nesospingus speculiferus

Puerto Rican tody Todus mexicanus

Puerto Rican vireo Vireo latimeri

Puerto Rican woodpecker Melanerpes portoricensis

Red-eyed vireo Vireo olicaceus

Robin Turdus migratorius

Rock dove Columba livia

Roseate tern Sterna dougallii

Royal tern Sterna maxima

Ruby-throated hummingbird Archilchus colubris

Ruddy turnstone Arenaria interpres

Semipalmated plover Charadrius semipalmatus

Semipalmated sandpiper Calidris pusilla

Sharp-shinned hawk Accipiter striatus venatur

Slate-colored junco Junco hyemalis

Smooth-billed ani Crotophaga ani

Snowy egret Egretta thula

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Birds continued

Troupial Icterus icterus

Turkey vulture Cathartes aura

White-necked crow Corvus leucognaphalus

Yellow-crowned night heron Nyctanassa violacea

Yellow-shouldered blackbird Agelaius xanthomus

Yellow warbler Dendroica petechia

Corals

Boulder star coral Montastrea annularis

Brain coral Diploria spp.

Branched fire coral Millepora alcicornis

Cactus coral Isophyllia sinuosa

Common brain coral Diploria strigosa

Common rose coral Manicina areolata

Depressed brain coral Diploria labyrinthiformis

Elkhorn coral Acropora palmate

Finger coral Porites spp.

Flat-topped fire coral Millepora complanata

Foliose coral Agaricia agarites

Fused staghorn coral Acropora prolifera

Horned coral Acropora spp.

Ivory bush coral Oculina diffusa

Knobby candalabra coral Eunicea spp.

Lettuce-leaf coral Agaricia agaricites

Rose coral Manicina areolata

Shallow-water starlet coral Siderastrea radians

Staghorn coral Acropora cervicornis

Star coral Favia fragum

Starlet coral Siderastrea siderea

Stinging fire coral Millepora complanata

Thick finger coral Porites porites

Thin finger coral Porites furcata

Yellow porous coral Porites astreoides

Crustaceans 

Barber shrimp Stenopus hispidus

Barnacle Balanus spp.

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Crustaceans continued

Crabs Aratus pisonii

Goniopsis cruentata

Grapsus grapsus

Edible land crab Cardisoma guanhumi

Green mantis shrimp Gonodactylus oerstedii

Oyster Crassostrea spp.

Purple-clawed land crab Coenobita clypeatus

Small green crab Mithrax sculptus

Snapping shrimp Crangon formosus

Spiny lobster Panulirus argus

Tiger lucine clam Codakia orbicularis

Wood-boring isopod Sphaeroma terebrans

Fish 

Ballyhoo Hemiramphus brasiliensis

Banded butterflyfish Chaetodon striatus

Banded puffer Spaeroides spengleri

Barracuda Sphyraena barracuda

Blueheaded wrasse Thalassoma bifasciatum

Blue striped grunt Haemulon sciurus

Blue tang Acanthurus coeruleus

Caribbean lobsterette Metanephrops binghami

Caribbean snapper Lutjanus purpureus

Catfish Ictalurus spp.

Damsel fish Stegastes spp.

Fairy basslet Gramma loreto

Four-eyed butterfly fish Chaetodon capistratus

French grunt Haemulon flavolineatum

Gobies Gobiosoma spp.

Gray angelfish Pomacanthus arcuatus

Hamlets Hypoplectrus spp.

Large-mouthed bass Micropterus salmoides

Lizardfish Synodus saurus

Parrot fish Ablennes hians

Porcupine fish Sparisoma radians

Pork fish Anisotremus virginicus

Puffer fish Diodon holocanthus

Queen angelfish Holocanthus ciliaris

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Fish continued

Queen parrot fish Scarus vetula

Queen trigger fish Balistes vetula

Rainbow parrot fish Scarus guacamaia

Red hind seabass Epinephelus guttatus

Sergeant major Abudefduf saxatilis

Spade fish Chaetodipterus faber

Squirrel fish Holocentrus rufus

Sunfish Lepomis spp.

Surgeon fish Acanthurus chirurgus

Acanthurus bahianus

Tarpon Megalops atlanticus

Trout Salmo spp.

Trumpet fish Aulostomus maculautus

Mammals

Antillean manatee Trichechus manatus manatus

Black rat Rattus rattus

Bulldog fishing bat Noctilio leporinus

Bumblebee bat of Thailand Craseonycteris thonglongyai

Finback whale Balaenoptera physalus

Giant tree shrew Solenodon paradoxus

Humpedback whale Megaptera novaeangliae

Indian mongoose Herpestes auropunctatus

Jamaican fruit bat Artibeus jamaicensis

Puerto Rican hutia Isolobodon portoricensis

Red fruit bat Stenoderma rufum

Rhesus monkey Macaca mulatto

Sei whale Balaenoptera borealis

Sperm whale Physeter macrocephalus

Mollusks 

Amber pen shell Pinna carnea

Atlantic modulus Modulus modulus

Bleeding tooth nerite Nerita peloronta

Checkered nerite Nerita tessellate

Common prickly winkle Nodilittorina tuberculata

Fighting conch Strombus pugilis

Flamingo-tongue snail Cyphoma gibbsum

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Mollusks continued

Four-toothed nerite Nerita versicolor

Fuzzy chiton Acanthopleura granulate

Helmet conch Cassis tuberose

Marbled chiton Chiton marmoratus

Queen conch Strombus gigas

Red snail Littorina angulifera

Red octopus Octopus briareus

Reef squid Sepioteuthis sepioidea

Sea hare Aplysia dactylomela

Spiny pen shell Atrina seminuda

West Indian chiton Chiton tuberculatus

West Indian sea egg Tripneustes ventricosus

West Indian sea star Oreaster reticulates

White urchin Tripneustes esculentus

Zebra periwinkle Littorina zigzag

Reptiles 

African python Python regius

American alligator Alligator mississippiensis

American spectacled caiman Caiman crocodiles

Common garter snake Thamnophis sirtalis

Common green iguana Iguana iguana

Culebra giant anole Anolis roosevelti

Eastern painted turtle Chrysemys picta

Gecko Hemidactylus spp.

Green chameleon Anolis cristatellus

Green sea turtle Chelonia mydas

Hawksbill sea turtle Eretmochelys imbricate

Hicotea Trachemys stejnegeri

Leatherback sea turtle Dermochelys coriacea

Loggerhead sea turtle Caretta caretta

Mono ground iguana Cyclura stejnegeri

Mona Island boa Epicrates monensis monensis

Monito gecko Sphaerodactylus micropithecus

Puerto Rican boa Epicrates inornatus

Puerto Rican lizard cuckoo Saurothera vieilloti

Red-eared turtle Trachemys scripta

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Reptiles continued

Spectacled caiman Caiman crocodiles

St. Croix ground lizard Ameiva polops

Virgin Islands tree boa Epicrates monensis granti

West Indian rock iguana Cyclura spp.

Worm snake Typhlops spp.

Sea cucumbers, sea fans, sponges, stars, and worms

American eel Anguilla rostrata

Breadcrumb sponge Haliclona rubens

Brittle star Ophiothrix angulata

Brown sponge Chondrilla nucula

Common sea fan Gorgonia ventalina

Donkey dung sea cucumber Holothuria mexicana

Feather duster worm Sabella melanostigma

Fire sponge Tedania ignis

Fire worm Hermodice carunculata

Gray sponge Ircinia spp.

Green moray eel Gymnothorax funebris

Large hairy brittle star Ophiocoma echinata

Magnificent feather duster Fregata magnificens

worm

Moon jelly Aurelia aurita

Ostrich plume Pseudopterogorgia Americana

Pencil urchin Eucidaris tribuloides

Polychaete worm Sabella spp.

Red sponge Haliclona rubens

Sand dollar Mellita lata

Sea fans Gorgonia spp.

Sea rods Pseudoplexaura spp.

Southern stingray Dasyatis Americana

Small sea cucumber Microthele parvula

Spiny brittle star Ophiocoma echinata

Split pore sea whip Plexaurella grisea

Spotted eagle ray Aetobatus narinari

Upside-down jelly fish Cassiopeia frondosa

Venus sea fan Gorgonia flabellum

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Urchins 

Black-spined sea urchin Diadema antillarum

Common urchin Ehinometra lucunter

Green sea urchin Lytechinus variegates

Heart urchin Clypeaster rosaceus

Large heart urchin Meoma ventricosa

Red rock urchin Echinometra lucunter

Other animals

Honeybee Apis mellifera

Seahorse Hippocampus reidi

Termite Nasutitermes costales

Tunicate Clavelina spp.

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This page is intentionally left blank.
Appendix 2: Visiting Puerto Rico 

For those visitors, instructors, and students who have not been on an extended field 

trip to a foreign tropical country, following is a list of suggestions you may find

helpful.

Definitely take along:

➢ Flashlight (preferably one that can be used when wet)

➢ Comfortable shoes (at least two pairs)

➢ Field shoes (ankle high preferable)

➢ Street shoes (that can double for dress)

➢ Travelers’ checks - any extra cash should be in the form of travelers checks. 

If lost or stolen, they are replaceable; “Don’t leave home without them!”

➢ Sweatshirt, sweater, and/or wind breaker with hood (preferably water 

repellent)

➢ Summer-weight sleeping bag or light blanket/sheet. You may be responsible 

for your own bed clothing and towels in some housing accommodations

➢ Sunglasses with UV protection

➢ If you are preparing your own food, take your own eating utensils: knife, 

fork, spoon, cup, plate, and bowl. It saves having to buy them

➢ Suntan lotion

➢ Sun hat (wide brim)

➢ Small day pack for field trips

➢ At least two photo IDs are required for airlines. No passport or VISA

required for U.S. citizens going to Puerto Rico. If anyone in the group is

a foreign national, a passport will be required.

For those groups planning on marine field trips:

➢ Old sneakers for walking on dead coral, but without holes in the soles. 

These could double for field shoes above, but wet shoes can be 

uncomfortable.

➢ Face plate, snorkel (breathing tube), and flippers (solid heel). You want a 

good fit (mouth, head, and feet to avoid blisters and cramps). If your group 

is scuba certified, plan on taking everything you need for the dive. There 

are dive shops in many communities so you can get access to replacement 

supplies if equipment breaks. Rentals are available and full-day reef dives 

are commercially available in the La Parguera and Fajardo areas (see 

ecotourism section).

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➢ Buoyancy compensator or life vest. You will need some form of buoyancy 

for trips onto coral reefs, mangrove swamps, and turtle grass beds. Rental 

boats will provide orange Coast Guard-approved vests.

➢ Old pair of pants and shirt for diving to protect you from the sun and coral

abrasion.

➢ Gloves for diving, preferably with leather palm. These are vital! Many 

organisms are sharp and have stinging cells.

➢ If you plan to take pictures, buy your film in the United States. It will be a 

little cheaper. Cheap underwater cameras work well in water up to 12 feet 

deep

➢ Plastic bag for wet clothes

Things you may find useful:

➢ Small quantity of insect repellent (rarely needed)

➢ Small first aid kit (alcohol, band aids, aspirin, matches, needle, bactericide

jelly, forceps, and thermometer)

➢ Binoculars–at least three pairs for the group, depending upon class size

➢ Extra pair of eyeglasses, if you require prescription glasses

➢ Knife (Do not carry it on your person or in a carry-on bag–it will be 

confiscated.)

➢ Small pocket Spanish-English dictionary

➢ Shower shoes (flip-flops)

➢ Know your blood type

➢ Be in as good physical condition as possible

➢ Dramamine for motion sickness (mountain roads and small boats)

To be kept in mind:

➢ Puerto Rico has universal access to potable water, one of the few islands in 

the tropical world that does. All water coming out of pipes can be assumed 

to be safe for drinking purposes. Never drink out of rivers, creeks, springs, 

or catchment basins. There are tropical diseases active there. Check with 

your local county health department for up-to-date health warnings for 

diseases like dengue fever. Be sure you are up to date regarding tetanus,

diptheria, polio, and so forth, prior to departure.

➢ There are no poisonous snakes, although there are some scorpions, 

tarantulas, black widow spiders, and poisonous plants.

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➢ Never swim in coastal brackish or lowland freshwater rivers under 457 

meters (1,500 feet) altitude. These are the habitats of a freshwater snail that 

is the vector for schistosomiasis. It is not present in saltwater or above 457

meters (1,500 feet) altitude owing to cold intolerance.

➢ Most Puerto Ricans are very friendly toward Americans or other foreign

nationals, and the majority of Puerto Ricans are bilingual. Most will be 

very helpful in providing directions or explaining local customs. There is 

an English language newspaper (The San Juan Star) and an English radio 

station in San Juan (1030 AM).

➢ Regarding food, we have not had any bad experiences in previous years as 

to sanitary preparation. Please keep in mind that you will have the opportunity to taste the food and drink of another culture. Hopefully, you will 

find their dishes more interesting and palatable than hamburgers or typical

stateside offerings. Although, if you must, stateside fast food outlets are 

found everywhere.

➢ Do not overpack. For most field trip groups, there is limited vehicle space 

and storage in your housing.

➢ Remember that you are a member of a group; keep your gear organized 

and respect others’ rights and equipment. You’ll likely be living in close 

quarters. Many instances will arise when you will have to make a decision 

on the basis of majority rule with regard to the schedule, meals, and so 

forth. Please be open-minded.

➢ Many units of measure, that is, gasoline purchases, mileages on road signs, 

will be expressed in metric units. You may find a small wallet-sized conversion chart handy. On the other hand, food is usually sold by the ounce 

or pound. Air temperatures are usually expressed in Fahrenheit. There is a 

metric conversion chart included on pages 310–311.

➢ If you are cooking, do not carry food from the United States. Puerto Rico’s

food stores offer great variety today, a combination of local and U.S. 

brands. This is an opportunity to see the variety of locally grown/processed

products from Puerto Rico compared to those of the United States. Try as many 

local products as you can.

➢ The U.S. Postal Service processes mail in Puerto Rico, and all mail to the 

continental United States will automatically be airmail and cost the same 

as when mailed in the United States.

➢ The legal drinking age in Puerto Rico is 18 years old. This can be a 

problem for some U.S. students who decide to experiment with alcohol for 

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Guide To The Ecological Systems Of Puerto Rico
the first time. In addition, rum is very cheap because there are no federal 

taxes applied to Puerto Rican rums consumed on the island.

➢ Puerto Rico runs on Atlantic Standard Time year round, which is 1 hour 

ahead of Eastern Standard Time (October-April), but is the same time as

Eastern Daylight Savings Time (April-October).

➢ Sun protection is needed by most visitors to the tropics to block harmful 

ultraviolet rays. Sunglasses, wide brim hats, and clothing cover for the 

body work best. For those areas exposed, use a sunblock with at least an 

SPF of 15 (95 percent protection). An SPF of 30 only increases protection 

to 97 percent. SUNBURN IS DANGEROUS.

➢ Phone calls are just like in the United States. Puerto Rico’s area codes are 

787 and 939. Calls will be charged like any other out-of-state call. You do 

not have the complications or expense associated with international calls. 

All local calls are 10 or 11 digit numbers, that is, they all include the area 

code (most are 787) and, depending upon your location in the island, add 1.

➢ Puerto Rico uses U.S. currency, so there is no exchange problem. United 

States traveler’s checks are accepted as cash. Be sure to have identification

with you. If you are buying something and the price is quoted in pesos, just

remember that a peso is equivalent to a U.S. dollar, thus cinco pesos is $5.

Purchases:

➢ Puerto Rico is not a tax-free port as you find in the nearby U.S. Virgin 

Islands.

➢ If you do not travel to another foreign country during your visit to Puerto 

Rico, you will not go through U.S. customs when coming to or departing 

from Puerto Rico. If you take a side trip to the Dominican Republic, the 

Virgin Islands, or other islands in the West Indies, you will have to undergo 

a customs check and declaration.

➢ If you are 21 or over, you are entitled to return to the United States with 1 

gallon (5 fifths) of Puerto Rican rum free of stateside duty and tax, but you 

will pay commonwealth tax at the time of purchase. Most other purchases 

are not tax advantaged, other than sales tax.

➢ You will be subject to a personal luggage check when departing San Juan 

by the U.S. Department of Agriculture. They will be checking for fresh produce (mangoes, pineapples, oranges, and so forth) and tropical plants and 

animals that may vector diseases or be potentially damaging alien species if

accidentally released into the United States. Any banned organisms will be

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confiscated without compensation. You can receive a list of prohibited items

when you arrive in the airport by visiting one of the USDA inspection booths

located in the departures area of the airport.

U.S. Regulations Regarding Collection and Purchase of 

Organisms:

➢ Any collecting of organisms for scientific purposes will require advance 

permitting from the U.S. government and Puerto Rico’s Department of 

Natural and Environmental Resources. Without permits, they will likely be

confiscated, and you may face fines. Some products made from species 

protected by the Convention on International Trade in Endangered Species

(CITES) agreements are still being sold illegally. More than 800 species are

banned, and trade in 30,000 items is controlled by CITES and other agreements throughout the world. Their possession can produce big fines.

➢ Four publications will help you to know what is or is not legal in terms of 

U.S. Customs, Agriculture Department, and Fish and Wildlife regulations.

➢ Department of the U.S. Treasury. 1983. Know before you go. Washington,

DC: U.S. Customs Service. 

For copies, write to: U.S. Customs

P.O. Box 7407

Washington, DC 20044

(202) 566-8195

➢ U.S. Department of Agriculture. 1994. Traveler’s tips. Program Aid No.

1083. Animal and Plant Health Inspection Service (APHIS). This brochure 

is also available at the San Juan airport, departure section.

For copies, write to: USDA

APHIS

Washington, DC 20250

➢ U.S. Department of the Interior. 2000. Facts about federal wildlife laws.

Washington, DC: U.S. Fish and Wildlife Service. Also available at the San 

Juan Airport, departures section.

For copies, write to: U.S. Department of the Interior

USFWS

Office of Law Enforcement

4401 N Fairfax Drive

Room 520

Arlington, VA 22203

(703) 358-1949

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Guide To The Ecological Systems Of Puerto Rico
➢ World Wildlife Fund. 1997. Buyer beware.

For copies, write to: World Wildlife Fund

1250 24th St., NW

Washington, DC 20037

Medical problems and prescription drugs:

➢ If you have any physical limitations, make sure the project leader knows 

about them prior to your departure. You do not want to get into a crisis 

situation in the ocean or on top of a mountain. 

➢ If you take prescribed medicine, be sure to have a current prescription with 

you and the medicine in the original container. Any form of drug consumption that is not legal will jeopardize the entire group and could land you in 

jail! Penalties can be severe and costs associated with court cases will be

expensive.

Auto rentals:

➢ Any person renting an automobile must be at least 25 years old. All major 

auto rental firms are available at San Juan International Airport or in the 

major cities on the island. 

➢ Before you leave home, be sure to check with your credit card corporations,

personal automobile insurance coverage, and/or your institutional insurance

coverage regarding international rentals and any coverage that is extended 

to you by the above. Insurance coverage will greatly increase rental costs

because it is sold on a day-to-day basis. Be sure to have adequate insurance

coverage, as it is not uncommon for the party with the “deepest pocket” to 

be held liable.

The indigenous ceremonial parks near Ponce and Utuado

An interesting field trip for any student or ecotourist group is to visit one of the 

indigenous ceremonial parks. The easiest park to access is the Tibes Indian ceremonial site, which is 15 minutes north of Ponce on Road 503 at kilometer 2.5. There

is a nominal entry fee of $2.00 for adults and $1.00 for children. This park features

the pre-Taíno Igneri culture. It has a series of displays, an artifact museum, and

outside bateyes, plazas, a burial area, petroglyphs, and other stone exhibits. 

A second indigenous ceremonial park is located near Utuado. It is accessed by

taking Route 10 to Utuado and then Route 111 west to kilometer 12.3. The site is

just past the Route 621 intersection. The Caguana Indian Ceremonial Park also has

a museum and was used as a major ceremonial area with bateyes and plazas. It was

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built in the 1200s. Admission fee is a contribution. Both parks are botanical gardens and have educational staff on site. Descriptive literature is available for selfinterpretation, and educational tours can be arranged by appointment.

Phone: Tibes - (787) 840-2255. Open daily except Monday 9:00 a.m. to 4:00 p.m.

Caguana - (787) 894-7325. Open daily except Monday 9:00 a.m. to 5:00 p.m.

El Morro and nearby colonial period buildings

El Morro is now a national historic site and part of the U.S. Department of the

Interior’s National Park Service. Open throughout the year and designated as a

world heritage site, it was recently used in the filming of Amistad, a movie about

an African slave revolt in 1839 on a Spanish merchant ship. El Morro means

“headland,” and it was so named because of its position overlooking the Atlantic

Ocean and all of San Juan Bay. There is a nominal entrance fee that includes viewing of a historical video, museum, and self-guided walking tour. Ranger tours are

available periodically throughout the day (11:00 a.m. and 3:00 p.m. in English). El

Morro is located at the tip of Old San Juan. A visit to El Morro is worthwhile and

up to half a day should be devoted to its full exploration. For those who enjoy 

period military history, two other forts are located nearby—San Cristobal and 

San Gerónimo. If you have time, both are worth visiting. Wear comfortable shoes

because you will have a long walk to access El Morro, since parking is restricted in

the area. It is open daily 9:00 a.m. to 5:00 p.m. The entrance fee is $3.00 for adults

(16 to 61) $2.00 for seniors (62 and above), and free for children up to the age of

15 years. Phone: (787) 729-6960. If time permits, visit La Fortaleza (Governor’s

mansion - circa 1630), Casa Blanca (Ponce de Leon’s home - 1523), and Iglesia

San José (among the oldest churches in the New World - 1522). All are within easy

walking distance of El Morro.

Serpentine outcrops near Maricao 

Serpentine outcrops can be easily observed along Route 120 in the Maricao 

Commonwealth Forest. Route 120 can be accessed off Route 2 at Sabana Grande.

There are large road cuts in the areas near Monte del Estado. From the observation

deck west of the Monte del Estado Vacation Center is a magnificent view of the

entire southern coast from Boquerón Bay to Guánica Commonwealth Forest;

including all of the Lajas Valley (take your camera, binoculars, and road map).

The karst landscape with a visit to the Caves at Camuy

One of the best places in the Western Hemisphere to see the various elements of 

karst topography are the Caves at Camuy. While driving there you pass through

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Guide To The Ecological Systems Of Puerto Rico
miles of haystack hills. Once there you will be able to tour the largest solution

cave open to the public in the Caribbean. It has stalactites, stalagmites, an underground river (the Río Camuy), and a large population of bats. In addition, you can

also ride a tram and walk via a boardwalk down into two very large sinkholes. This

is also an excellent opportunity to see the unique vegetation typical of these areas.

This is a commercial operation with a set number of tickets sold each day ($10.00

for adults; $6.00 for children). The admission also includes the tram rides and sinkhole access. To visit the caves, take Route 22 to Arecibo. The park entrance is off

Route 129. Driving time is about 2 hours from San Juan. 

Buried deep in the karst region of the north coast is one of the great technological marvels of astronomy, the Arecibo Ionospheric Observatory. It is located

near the caves. Take Route 635 to 625, and you will find the observatory at the end

of 625. See the karst forest section for further description of the observatory. The

observatory has an excellent visitor center and public education program.

The Ponce Cement plant 

An interesting field trip incorporating mining, manufacturing, fossil collecting, and 

pollution control can be scheduled with a visit to the large Ponce Cement Company

plant in Ponce. This is one of the largest commercial cement operations in the

Caribbean and will permit interested educational groups to see surface mining

operations, manufacture of both wet and dry cement, and modern pollution control

systems mandated by both the U.S. Environmental Protection Agency and Puerto

Rico Environmental Quality Board. In addition, a site visit to areas currently being

mined for limestone will make it possible to collect large quantities of fossil clams,

heart urchins, scallop shells, as well as crinoid stems. The operational mines are

ongoing in areas adjacent to the plant just west of Ponce on Route 10. Contact:

Puerto Rican Cement at (787) 842-3000.

The University of Puerto Rico’s Botanical Garden

An excellent way to gain an introduction to the tropical flora, especially woody 

species, is to visit the Botanical Garden at the University of Puerto Rico/

Experimental Station campus in Río Piedras. The garden has hundreds of species

on display. There are two sections to the garden. The upper section has an outside

orchid display. It suffered heavy damage during Hurricane Georges and is being

replanted. Many of the plants have identification tags. It is located off the intersection of Route 1, Route 3, and Route 847. The garden is open daily from 9:00 a.m.

to 4:30 p.m., and there is no entrance fee. Tell the guard posted at the entrance that

you want to visit the gardens. Parking is available adjacent to the Jardin Botánico.

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Plan at least 2 hours for your self-guided tour. Guided tours for student or organized groups are available by appointment every day except Saturdays, Sundays, and

holidays. Special group tours on weekends are available upon request. For tours

call (787) 250-0000 or 767-1710. Associated with the Botanical Garden is a herbarium with 36,000 specimens in its collection. The garden is also used extensively

for cultural and social programs. Special displays in the garden include palms,

aquatics, heliconias, and orchids. A detailed garden map is available from the guard

as you enter the grounds. The university has another botanical garden on its

Mayagüez campus and it is open from 8:00 a.m. to 4:00 p.m. It is also free of

charge. It is located off Post Street. Phone: (787) 831-3435.

Animal observations

For those interested in viewing wildlife, D.W. Nellis’ (1999), Puerto Rico and 

Virgin Islands Wildlife Viewing Guide provides maps and descriptions of some of

the best wildlife areas to visit with photographs of species likely to be encountered.

Cost $9.00.

Should you be interested in viewing tropical animals, Puerto Rico has a 

recently expanded animal park in Mayagüez. The Puerto Rico Zoo is a 36.5-hectare

(90-acre) animal park displaying mostly tropical animals of the Caribbean, South

America, and Africa, with emphasis on mammals, birds, and reptiles. Entrance fee

is charged according to age. Open Wednesday through Sunday, 9:00 a.m. to 4:00

p.m., at Route 108, Mayagüez, Puerto Rico 00681. Phone: (787) 834-8110.

If you are interested in seeing butterfly art, one of the most interesting displays

is to be found in Old San Juan at “The Butterfly People Gallery.” It has displays of

magnificently colored butterflies in plexiglass boxes for mounting on walls or to

display on bookshelves. They range from individual animals in 13- by 13-centimeter (5- by 5-inch) boxes, to flight displays in boxes 3 by 2 meters (10 by 6.5

feet). All displays are for sale. As none are rare species and, according to the company, are artifically reared, they are legal. The gallery is located in an old home

known as the birthplace of Muñoz Marín, Puerto Rico’s first elected governor, and

is at 152 Fortaleza Street, about two blocks from the Governor’s residence. Phone:

(787) 723-2432.

How to capture a tree frog 

Tree frogs are relatively easy to capture by hand. This makes for an interesting 

evening field trip. Be sure to investigate any nocturnal field site during the day so

you do not inadvertently walk yourself or your class off the side of a mountain.

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Success in locating frogs is likely from any paved road with dense roadside vegetation or along any forest trail. You are fortunate in that you do not have to worry

about poisonous snakes or other dangerous animals while in the rain forest after

dusk. Look for frogs in leaf axils of tank epiphytes, under loose tree bark, under

folded leaves, and in limb holes. Sometimes, they may just sit on a leaf or branch

in full view, or they will be on the ground or a rock. All species are active at night.

The only real field trip needs are good flashlights or head lamps. Head lamps have

the added advantage of freeing up both hands for the location and capture process.

It is best to work in pairs. The study of tree frogs includes important ecological

topics such as habitat and resource partitioning, differential expression of vocalization in sexes within a species and among complex species groups, island biogeography, and rapid direct development as an adaptive strategy to cope with a 

terrestrial life cycle.

Where to bird watch

A free travel map of places to bird watch can be obtained from The Puerto Rico 

Convention Bureau. It clearly indicates all of the U.S. and commonwealth forests,

refuges, and preserves easily accessible for bird watching. See the map reference

section in appendix 4 for obtaining copies. See also the three sections on refuges

that follow. Phone: 1-800-875-4765.

Neotropical migrants in the Guánica Forest

The Guánica Forest can be accessed via Route 116, just east of the town of 

Guánica. Take Route 334 to the forest headquarters. An interesting field exercise 

is to do bird surveys in forested areas in order to determine native residents and

Neotropical migrants. The only equipment needed are binoculars and bird guides.

Bats in Camuy Caves

If you want to see a protected cave roost, take a trip to the Caves at Camuy. The 

caves are located off Route 129 19 kilometers south toward Lares. They sell limited tickets each day and they are open Tuesday through Sunday from 8:00 a.m. to 

5:00 p.m. Three levels of tour are available and the ticket prices vary accordingly.

Phone: (787) 763-0568. More details are included in the section on moist karst

forests.

The Bacardí rum distillery 

While in San Juan, you can take a free tour of the Bacardi rum distillery in Cataño. 

You can drive to it directly or take the Cataño ferry from the ferry depot in Old San

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Juan and then take a taxi to the plant. The company store sells many Bacardi products, all emblazoned with the black bat logo. The plant is located on Route 165 at

km 2.6. Free tours are available 8:30 a.m. to 4:30 p.m. daily. Phone: (787) 788-

8400.

Guánica Forest 

To access this unique preserve, take Route 2 west of Ponce to Route 116 west. 

Route 334 goes to the heart of the forest and the education center. (Phone: (787)

724-3724.) It is open Tuesday through Sunday, 9:00 a.m. to 5:00 p.m. with no

entrance fees for individuals or small groups. There are 12 hiking trails and small

exhibits at the center. Be sure to have sun protection and your own water supply.

This is a warm habitat. A second road (Route 333) runs along the coast where you

can observe scenic beaches, seagrass beds, limestone hills, rocky headlands, and

fringing red mangrove communities. A trail guide and description of the forest and

its species is available from Sr. Miguel Canals, P.O. Box 985, Guánica, Puerto Rico

00653.

To see a variety of coastal species and dry habitats, visit the Las Cabezas

Nature Reserve. For the rain forest species and habitats, visit the nearby Caribbean

National Forest. 

For those individuals or groups who have a limited amount of time for field

trips but yet want to see a good cross section of the habitats, species, and ecosystems typical of Puerto Rico and the Caribbean just described, the following visits

are recommended. Two reserves, the Caribbean National Forest and the Las

Cabezas de San Juan Nature Reserve make the best combination of visits. They are

close to San Juan (44 kilometers [27 miles]) and they are only 18 kilometers (12

miles) apart. Both are just off Puerto Rico Route 3 in the northeast corner of the

island. We recommend 1 day for each site, which will permit you to take advantage

of the education programs, exhibits, hiking trails, and opportunities to discuss the

various species and systems being observed. Both areas have good maps and technical literature available for those wanting a detailed description of the habitats to

be studied. Both have active public education programs and visitor centers. More

information of Las Cabezas is presented in the commonwealth reserves section.

Visiting the karst region of Puerto Rico

Classic karst landscape can be observed in a number of ways. A car trip from 

Arecibo to Utuado on Route 10 or Route 129 to Lares will take you through karst.

The major coastal road, Route 22 from San Juan will take you through a degraded

section of haystack hills. Many are disappearing in this area as a result of urbaniza373

Guide To The Ecological Systems Of Puerto Rico
tion, road construction, and mining for aggregate. Some of the best karst can be

observed in the area around the Arecibo Observatory at the end of Route 625. This

trip has the added benefit of offering the opportunity to view the radio telescope.

For more detailed exposure and the opportunity to walk in the karst belt, there

are four options. There are three Puerto Rican commonwealth forests at Guajataca,

Río Abajo, and Cambalache with miles of maintained paths through the formations.

Guajataca Commonwealth Forest is west of Arecibo and Río Abajo is south of

Arecibo. Cambalache is east of Arecibo just north of Route 22. For many, the best

option is the Río Camuy Cave State Park, south of Arecibo. This 109-hectare (268-

acre) ecosystem provides easy access to a large solution cave, extensive sinkholes,

and one of the largest underground rivers in the Western Hemisphere. The caves

are a reported 45 million years old. One of the sinkholes is accessible via a 205-

step staircase to the bottom. It provides an excellent view of sinkhole vegetation.

Educational interpretation is a part of the tour. Entrance fees are $10.00 for adults;

children, seniors, and groups receive reduced rates. The park is open Tuesday

through Sunday at 8:00 a.m. The last tour departs at 3:45 p.m. (707) 763-0568.

Please note, cave exploration in Puerto Rico is dangerous. Many are unexplored and remote, and rescue would be difficult in the event of an accident.

Individuals or groups planning cave exploration need to be experienced, with all

the necessary safety gear and a full plan on file with someone who can verify the

safety of the group. Remember many caves have black hole drops, and a rain event

miles away may drastically change the conditions in an underground river in minutes without any warning to the spelunkers.

How to access the Arecibo Ionospheric Observatory 

The National Astronomy and Ionosphere Center and Arecibo Observatory—the 

largest radio/radar telescope on earth with an 8.1-hectare (20-acre) radar dish—is

located in the heart of the karst region. Driving time is 30 minutes south from

Arecibo. Take Routes 22 → 129 → 134 → 635 → 625. The observatory is at the

end of Route 625. Visiting hours are 12:00 to 4:00 p.m., Wednesday to Friday;

Saturday and Sunday, 9:00 a.m. to 4:00 p.m. Phone: (787) 878-2612. The facility is

built in a giant sinkhole, 305 meters (333 yards) in diameter and 172 meters (188

yards) deep and surrounded by haystack hills. The public visitation center has

many astronomy and climate educational exhibits and interactive facilities, plus a

video that describes its development and operation. Admission fee is $4.00 for

adults and $2.00 for students and seniors. It is funded by the National Science

Foundation and operated by Cornell University. Its main emphasis is using radar

astronomy to determine information about planets, asteroids, comets, and the

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moon. The use of radio astronomy allows for the study of energy emitted by 

galaxies, stars, clouds of gas, pulsars, and quasars. There is great interest in searching for evidence of extra-terrestrial intelligence by detection of their radio signals.

The observatory was featured in the film “Contact.”

Visiting the rain forest—first start at the gateway (El Portal)

Most visitors to the tropics want to see a rain forest. In Puerto Rico your best 

option is to visit the Caribbean National Forest, the only tropical rain forest in the

USDA National Forest System. This 11 200-hectare (28,000-acre) forest has more

species of trees than all the other forests in the National Forest System put together.

It can be reached from San Juan by taking Route 3 east to Palmer, then Route 191

through the forest. Initially stop at the U.S. Forest Service Education Center, El

Portal (the Gateway), where you can view many exhibits on tropical plants, animals, products, etc. There is also a movie that introduces you to the forest. It has 

a bookstore and a concession stand. Entry fees are $3.00 for adults, $1.50 for children and seniors. From there, you can spend the rest of the day driving and hiking

the trails in the various sections of the forest. Phone: (787) 888-1810. 

If you have an extra day or two, you can drive the Panoramic Route through

the heart of the mountains from the east coast to the west coast. This 275-kilometer

(165-mile) journey, over a collection of 40 roads, will permit you to see a variety

of montane forests and agroforestry systems. This is not a road for those who 

experience motion sickness.

Visit to Hacienda Buena Vista

Hacienda Buena Vista is an old coffee plantation representative of the 19th century. 

It is a period plantation museum, with excellent examples of 1800s-era processing

technology and uses the diverted waters of the Cañas River to supply power for 

the Hacienda. Coffee from the Hacienda was exported to the United States and

Europe. It also processed corn meal and grew as cash crops a variety of fruits and

vegetables, many of which are on display as you walk the trails at the Hacienda.

Hacienda Buena Vista is located 17 kilometers (10 miles) northwest of Ponce 

on Route 10. The facility is a property of the Conservation Trust of Puerto Rico,

which specializes in managing properties of special ecological, historical, or aesthetic value. Entry fees differ for groups and by age. General entrance is $5.00, for

adults, and phone reservations are recommended because they limit entry and are

open on selected days. To make reservations, call (787) 722-5882. For advanced

information or reservations, contact the Conservation Trust at P.O. Box 902355,

San Juan, PR 00902-2355.

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Visit a large regional produce market

If you have time, you should try to visit a large regional fresh produce market to 

see the wide variety of tropical fruits and vegetables for sale. If you are in Río

Piedras, a large fresh produce/meat/fish/medicinals market is located in the center

of town, one block from the bus terminal. There is an underground parking garage

and most of the shop managers will be able to provide you local names, common

uses, and how to prepare their products. While there, you can taste raw cold

coconut milk, maví (fermented bark drink of the maví tree), and a variety of other

local products. Unfortunately, many local markets are disappearing as a result of

the rapid expansion of the large food chains now found throughout the island. 

Visiting the Tortuguero Lagoon National Reserve, an exceptional wetland 

complex 

Tortuguero Lagoon is one of the best habitats to visit to see a freshwater marsh on 

the north coast. It is located off Route 2 on Route 687 north. This area is designated the Laguna Tortuguero National Reserve and will be sign-posted on the left.

Tortugero Lagoon is 1.6 kilometers (1 mile) from the open coast. The lake depth is

up to 3 meters (10 feet) and is fed by underground water from the limestone hills.

It is slightly salty owing to salt spray and its connection to the sea. The bottom of

the lake is sandy as a result of the decay of limestone and coastal sand accumulation. This is a good habitat to observe Potamogeton (pondweed), Najas (water

naiad), Utricularia obtusa Sw. (insectivorus bladderwort), Nymphaea odorata Ait.

(white water lily), Typha domingensis Pers. (cattail), Cladium jamaicense Crantz

(sawgrass), Rhynchospora gigantea Link (giant sedge), Hibiscus spp. (hibiscus),

Annona glabra L. (pond apple), Blechnum serrulatum L. (toothed fern), and a wide

variety of other wetland species. The area has a series of wetland community types

to observe:

➢ Submergent vegetation

➢ Open-water marsh—floating leaves

➢ Emergent marsh

➢ Marl prairie

➢ Seasonal swamp thicket

➢ Evergreen hedge/thicket

➢ Seasonal swamp woodland

➢ Wet savanna

➢ Seasonal semievergreen forest

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The area has a clay hardpan under the surficial sands. Coupled with slight 

increases in soil depth this results in different drainages and plant zonations. There

are also marl deposits present with a pH of 8.0, which is very diverse in sedges.

Take a shovel and dig a soil pit to expose the clay hardpan. The hardpan impedes

water and root penetration, thus species composition of the communities present

differ with the changing soil conditions.

Wild populations of the primitive gymnosperm, Zamia (cycads), are present.

Drosera intermedia Hayne (insectivorous sundews) are present in the marl prairie

habitat, as is Sphagnum (peat moss). There are also ground and arboreal orchids.

This area has Comocladia (poison plant) and Anacardium occidentale L.

(cashew), which is poisonous if the nut is not cooked to denature the toxins in the

oils. Both of these are members of the Anacardiaceae (cashew) family.

The lagoon has a variety of fish, turtles, and now an introduced population of

Caiman crocodilus (American spectacled caiman).

Visit Las Cabezas for a good introduction to coastal zone habitats and species 

A good place to see the interface of the outer coastal zones and the sea is at Las 

Cabezas de San Juan Nature Reserve in Fajardo. In this one area, the visitor can

see coral reefs, seagrass beds, sandy beach, rocky beach, mangrove forest, and dry

forest. This is an excellent opportunity to examine a series of interactive systems

and learn about the species and the factors that control their distribution. Nearby

are examples of areas that were once like the reserve’s natural habitats and have

now been developed.

Mangrove Field Trips

Mangrove forests are accessible in most sections of the island because many of 

the forests are part of the growing conservation/preservation efforts by both 

governmental and nongovernmental organizations. The public is now interested in

learning about and visiting these unique plants and the complex ecosystem they

support. Mangrove areas with easy access are highlighted in table 22. Most have

education facilities on site.

Phosphorescent Bay 

Puerto Rico has one of the most famous “phosphorescent” bays in the world 

spurring the growth of a major ecotourist business on the southwest coast in the

village of La Parguera. Bioluminescence is the emission of light from an organism.

Most people identify this process with the common firefly. This phenomenon was

first recorded by Robert Boyle in fungi, but a wide range of other organisms such

as bacteria, insects, annelids, marine invertebrates, and fish have this ability.

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Bioluminescence results from a chemical reaction of luciferin and luciferase,

whereby chemical energy is converted to radiant energy at a level close to 100 

percent efficiency. This means that little heat is produced and the luminescence is

referred to as cold light. There is a technical difference between the processes of

bioluminescence and phosphorescence. If organisms emit light stored for some

time as electric energy from a previous exposure to light, they are referred to as

phosphorescent. So the bay at La Parguera is really a bioluminescent bay.

Why the bay at La Parguera and what organism causes this phenomenon? The

small bay in Puerto Rico is approximately 24 hectares (60 acres) and surrounded

by mangroves on 90 percent of its shoreline. The mangrove community is dominated by Rhizophora mangle (red mangrove). The water of the embayment is protected on the seaward side by two small hills and with a geologic sill at the mouth of

the bay. This promotes calm water with a low exchange rate. The benthic zone is

composed of the seagrasses Thalassia testudinum Konig (turtle grass), Halophila

baillonis Ascherson (mid-rib seagrass), and up to 50 macrobenthic algae species

(Almodovar and Bloomquist 1959). The water of the bay is nutrient rich, which

may account for the presence of large populations of the bioluminescent dinoflagellate (fire algae) Pyrodinium bahamense. According to Burkholder et al. (1967),

there are 17 species of dinoflagellates in the bay, with Pyrodinium bahamense the

most common. When P. bahamense is mechanically stimulated (fish swimming,

waves crashing, or motor boat props, and so forth) it bioluminesces. A bucket of

sea water from the bay will contain thousands of them. When a person disturbs the

water, the water in the bucket “lights” up. At night, motor boat props produce a

glow bright enough to read newsprint by and the bay is often called “a sea of fire.”

The bioluminescent light effect is viewable throughout the year.

What value does bioluminescence have to the species? For some it promotes

location of sex partners, for others it promotes capture of food organisms, and for

others it promotes escape from predators or disguise. In the case of dinoflagellates,

like Pyrodinium, there is currently no known value.

In the last 20 years there seems to have been a reduction in the visual intensity

of the bioluminescence at La Parguera. This is due to a variety of factors such as

the large number of boats visiting the bay in prime time; light from the street lights

of the community behind the mangrove fringe; reduction of the mangrove fringe;

sky shine from the general growth of La Parguera’s expanding houses, businesses,

lighted parking lots, and the nearby yacht club; and regional sky shine from the

general growth along the southwest coast. The Phosphorescent Bay is truly the

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“goose that lays the golden egg” and hopefully will be protected for future generations. It is the economic base of one of the region’s major attractions. People 

from all over the world come to Puerto Rico and La Parguera just to visit La Bahía

Fosforescente. The red and black mangrove fringe around this bay is of great concern to the Puerto Rican Department of Natural and Environmental Resources

because it is being degraded by heavy commercial and recreation boat traffic,

houseboats, and general tourist recreation in the bay. However, the department 

has the power and responsibility of protecting this resource. The fringing forest is

now one of the properties being managed by the Conservation Trust of Puerto Rico

(fig. 89).

Trips to La Bahía Fosforescente are available year round. Each evening, party

boats of various sizes make 40-minute trips to the bay. They leave on the hour generally from 8:00 p.m. to midnight. Cost is $5.00 per person. Take a windbreaker as

it may be cool. If you have the option, try to time your visit when the moon is less

full. Moonlight can reduce the visual effect significantly.

For more information on Phosphorescent Bay see Hastings 1968 and Seliger 

et al. 1971.

Accessing seagrass beds

One of the best places in Puerto Rico to study seagrass beds is the vicinity of 

La Parguera. La Parguera in the 1960s was a small fishing village. Today, it is a 

thriving tourist town largely because of its proximity to the world famous

Phosphorescent Bay and the easily accessible coral reefs for snorkeling, scuba 

diving, and other water sports. There are dozens of islands in the waters of La

Parguera, and a large cluster of fringing mangrove swamps line the shoreline. In

association with the islands and swamps are large, well-developed seagrass beds.

Many beds are to the rear of nearby coral reefs where they occupy the calm waters

of the protected lagoons, whereas others occur in the channels and lagoon areas

associated with the mangrove swamps on the sublittoral edge.

Access to these seagrass beds is relatively easy. Many sandy beaches will have

seagrasses in the shallow water just beyond the wave zone. A good indicator is to

examine any beach debris for the presence of seagrass leaves. Many seagrass beds

are accessible simply by finding a break in the red mangrove thicket and entering

the open water in front. Usually, a turtle grass bed will be present. A more interesting method to access a wide variety of seagrass sites is to rent a boat from one of

the boat operators at La Parguera. You do not need to find them; they will have

street solicitors wanting to rent you boats as you drive to the seafront. Having a

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boat allows you to survey a variety of sites for species composition and variation in

growth and development of communities and populations under varying growth

conditions such as water depth, clarity, substrate composition, wave/tide action,

proximity to predator populations such as black-spined sea urchins, and a variety 

of human actions such as the shearing effect from motor boat props. All of these

features lend themselves to interesting personal observations, and they are worthy

of a marine ecology field trip studying a variety of taxonomic characteristics exhibited by each species and observations related to the presence of associated algae.

Be sure to look for indications of sexual reproduction and excavate the various

vegetative parts of the plants’, especially those involved in asexual reproduction.

Accessing the coral reefs of Puerto Rico

Among the most popular areas for sailing and boating are the areas around Puerto 

Rico’s many coral reefs. The areas in and around places like La Parguera and

Fajardo, with their generally pleasant weather and beautiful waters make sailing,

motor boating, and diving in the area a relaxing experience. However, the coral

reefs below the surface of the water must be taken into consideration. Grounding

your boat on a coral reef will not only damage the boat but also destroy coral structures that have been thousands of years in the making and are very slow to recover.

The following tips will allow people to enjoy their recreation and protect the reef.

“Brown, brown, run aground.” Coral reefs grow upward. When they are relatively close to the surface, coral formations will make the water appear brown.

Such areas should be avoided. If they are not, a boater will likely run aground or

slam the motor prop into coral.

“Green, green, nice and clean.” The areas behind and to the sides of a reef are 

often covered by green seagrasses. The only hazard to a boat is the rather shallow

water in some of these areas. Careless motoring through shallow turtle grass beds

can tear up the plants, however, and should be avoided because it is very destructive of the habitat and can lead to further erosion.

“Blue, blue, sail on through.” Areas where there is deep water, such as on the 

seaward side of a reef, appear blue. When sailing in blue water, however, remember that coral reefs rise rather abruptly from deep water. Give yourself plenty of

room to maneuver. It is best to have a spotter positioned in the bow of the boat to

warn the pilot.

Before sailing into any area close to reefs, boaters should thoroughly familiar380

General Technical Report IITF-35
ize themselves with the nautical charts for the area. They should pay particular

attention to depth indications. Navigational and Loran charts published by the

National Ocean Survey of the National Oceanic and Atmospheric Administration

are among the most reliable (see map section in app. 4).

If anchoring in a reef area, do not anchor on the reef itself, as anchors can

easily destroy coral. Anchor only in sandy areas. The bottom in sandy areas

appears white from the boat. Unfortunately, mooring buoys are not common in the

waters of Puerto Rico. They would greatly reduce recreation impact on reefs. A

few have recently been installed in reefs in the La Parguera area.

The coral reefs of Puerto Rico

There are a variety of ecotourist companies or commercial boat operators in the 

Fajardo area that specialize in 1 or more days of sailing, scuba diving, and snorkeling on the coral reefs in the waters between Puerto Rico, Culebra, and Vieques.

Prices generally start at $60 per person per day. The reefs can also be reached from

island beaches. Public ferries are available from Fajardo to both Culebra and

Vieques each day. Tickets cost $2.25 to Culebra and $2 to Vieques. For information

and reservation, call the Fajardo Ports Authority–(787) 863-0705. Públicos (public

taxis) will take you to the beach of your choice once you are on the island. 

A much more economical way to conduct a field trip with several students is 

to go to La Parguera on the southwest coast and rent individual boats. Boat rental

costs are negotiable, but you should assume that it will cost around $50 per boat,

per half day. Each boat can carry five to six people, and the required life jackets are

supplied. Each person will have to supply his or her own snorkeling or dive gear. It

is best to plan reef activities from 9:00 a.m. to 1:00 p.m. for two reasons. If you go

out too early, light conditions will be poor. The other reason relates to winds and

waves. By noontime, waves will be larger owing to wind and as a result, water

clarity will drop considerably. In addition, most student groups will be tired within

4 hours and be ready to have lunch.

The coral reef and seagrass bed easiest and cheapest to access is at the mangrove island locally called Isla Gato (Cat Island). It can be accessed by water taxi

from the seafront at one of the boat rentals. They will drop you off and pick you up

at a designated time. This island has a Department of Natural and Environmental

Resources dock, with a large protected swimming area. There are picnic tables, toilets, and shade. Coral reefs are to the front and sides of the island, and seagrass

beds to the rear on the protected side. The island has a red mangrove canopy and

provides good views of prop root zonation.

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Boat rentals are available from:

Cofresí Boat Rentals—(787) 899-4346

Pepe Boat Company—(787) 899-5025

Torres Boat Service—(787) 899-4281

Free parking is available behind the shops that line the water front. These boat 

rentals will also be willing to take your group to the Phosphorescent Bay in smaller

boats by reservation. They will negotiate a group discount of $1 off the large boat

price and generally give you more time in the bay.

Adjacent to the village of La Parguera is Magueyes Island, which is the field

station of the Department of Marine Sciences at the University of Puerto Rico 

at Mayagüez. This is a teaching and research facility that allows their graduate 

students to live and work at their research sites. Visits to their facilities can be

arranged by contacting the department at Mayagüez—(787) 832-4040.

Cabo Rojo National Wildlife Refuge field office 

The Cabo Rojo National Wildlife Refuge has a small visitor center with displays 

and a variety of brochures available to the public. Adjacent to the center is a 3-

kilometer (2-mile) interpretive trail and cactus garden. The visitor center is located

off Puerto Rico Route 301 at kilometer 5.1. Visiting hours are from 7:30 a.m. to

4:00 p.m. Monday through Friday. Staff biologists and an environmental educator

provide a variety of audiovisual lecture programs on topics such as endangered

species, sea turtles, and sea mammals. Programs require advance reservations (2

weeks or more), which can be made by contacting:

Environmental Education Office

Boquerón Field Office

P.O. Box 491

Boquerón, PR 00622

Tel: (787) 851-7297 Ext. 29

Fax: (787) 851-7440

The Laguna Cartagena refuge

The refuge has two entrances. Both require a walk to the lagoon. Take Puerto Rico 

Route 305 at Maguayo or route 306 south of Route 101 near Hacienda Desengaño.

The refuge is open 8:00 a.m. to 4:00 p.m. Hiking trails are self-guided. There are

no educational facilities or staff onsite.

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Appendix 3: Ecotourism

Nature, Adventure, and Diving Tours

Tourism is one of Puerto Rico’s largest industries (2 million hotel guests in 2002). 

Globally, tourism has been growing at nearly 4 percent per year. The fastest growing sector of tourism at around a 10-percent growth per year is ecotourism. The

ecotourism industry in Puerto Rico has grown rapidly in the last decade since its

advent in the early 1990s. Today, there are dozens of companies that offer a variety

of activities and destinations to virtually all important environmental areas on the

island. Tourism represents a potential threat to natural areas, especially to sensitive

sites such as coral reefs and cloud forests. Ecotourism, if properly designed and

managed, should permit humans to visit delicate sites and yet avoid or minimize

human impact. Ecotourism should always promote conservation, create economic

opportunities for local citizens and communities, and be sustainable. A major component of all ecotourism should be educating the visiting public regarding the basic

ecology of species and ecosystems visited, and how they are being affected or 

protected by oversight agencies and the surrounding community. Before making 

a reservation with any ecotourism company, it is recommended that the following

questions be asked. How much of the trip will emphasize education? What are 

they doing to minimize environmental impact? Do they have a published list of

ecotourism principles that they adhere to, such as:

➢ Provide sustainable benefits for the local community.

➢ Educate their client travelers.

➢ Encourage governmental and nongovernmental organization protection 

of the sites visited.

➢ Promote local conservation efforts with financial support.

➢ Adhere to principles of low-impact travel and environmental ethics.

➢ Work with other ecotourism companies to prevent overexploitation of 

sensitive species and habitats.

➢ Help design and build trails, lodges, and other infrastructures 

compatible with the ecosystem being visited.

➢ Are they members of the Ecotourism Society, and are they listed in 

their International Directory [(802) 447-2121]?

For those wanting to see “natural” Puerto Rico without going out on their own, 

ecotourism companies offer a variety of options that include set programs as short

as half-day trips to helping you create your own itinerary from 1 to 7 days. The

price typically includes transportation and a guide. Reservations are required.

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Guide To The Ecological Systems Of Puerto Rico
Entrance fees, overnight housing, air tanks, and so forth may not be included. 

The following is a list of companies offering services. Please note, these are not

endorsed by the authors as we have no experience in using any of their services.

Prices differ by length of trip and number in the group. Some of these companies

are not full-time operations so you may have to call at different times to have your

questions answered. Inquire about contracts, liability, payments, cancellations, and

inclusions. Prior to making reservations, “know before you go” regarding all fees,

what is supplied, and what happens in the event of a cancellation. Inquire about 

the size of the tour. Avoid large groups, as much of your time will be spent dealing

with large group logistics, and you will have less time to study the habitats and

organisms that you are interested in observing.

Company name Phone Trip options

Adven Tours (787) 530-8311 Mona Island and El Yunque trips, 

bird watching, hiking, camping

Aventuras Tierra Adentro (787) 766-0470 Various mountain hiking/camping 

trips, cave exploring, rappelling 

in sinkholes, and underground 

river exploration

Alelí Tours (787) 899-6086 Mangroves, coral reefs, and 

Guánica dry forest

Attabeira Educative Travel (787) 767-4023 Education trips to various destinations

Caribbean Reef Divers (787) 254-4006 Scuba/snorkel reef trips

Copladet Nature & (787) 766-0470 Education, nature, and recreation

Adventure travel trips throughout Puerto 

Rico

Coral Head Divers (800) 635-4529 Scuba/snorkel reef trips

Eco Action Tours and (787) 723-3113 Various water sports and hiking 

Watersports trips

Eco Xcursión Aquática (787) 888-2887 Water-based environmental tours

Encantos Ecotours (787) 272-0005 Various ecotours to multiple destinations, biking, and kayaking in 

Piñones Forest

Expediciones Montaña (787) 898-2723 Mountain treks

Adentro

Fajardo Tours (catamarans) (787) 863-2821 Sailing/snorkeling trips

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General Technical Report IITF-35
Company name Phone Trip options

Hill Billy Tours (787) 760-5618 “If it’s here, they will take you” 

Nature tours throughout the island

Normandie Tours (787) 722-6308 Rain forest and Camuy Caves

Paradise Island Ecotours (787) 832-7933 Trips to commonwealth reserves in

western Puerto Rico

Parguera Divers (787) 899-4015 Scuba diving 

Training Center training and dive trips

Piñones Ecotours (787) 253-0005 Biking and hiking trips in Piñones 

Forest

Sea Ventures (PADI (787) 863-0199 Diving/snorkeling 

Dive Center) (800) 739-3483 trips

Sunshine Tours (787) 810-4545 Rain forest, Camuy Caves, Arecibo 

Observatory, Phosphorescent Bay

For further reading, see Fennell 1999, Hess 1992, Honey 1999, McLaren 1998, 

and Whelan 1991.

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Appendix 4: Tools

Educational Wall Charts and Brochures of Ecosystems and Endangered 

Species

There have been numerous colorful wall charts and brochures developed by several 

public agencies and nongovernment organizations that depict a variety of ecosystems, processes, and species typical of the Caribbean and Puerto Rico. These documents are excellent visual aids for illustrating the complex nature of some of these

ecosystems and the species found there. Others are a pictorial overview of one or

more endangered species. Some are diagrammatic in format, whereas others feature actual closeup wildlife photography. All are very useful for educating various

public interest groups concerned with the environment. There is not one complete

listing for these various products; in fact, the agencies do not have complete listings for their products. The following list brings together some of the best products

of each agency and how to access them. Unfortunately, some of the agencies’ printing budgets do not allow multiple printings and as the supply runs out, they will

not be reprinted unless there is very high demand or new monies are allocated.

Sea Grant Program

Communication Section

University of Puerto Rico

P.O. Box 9011

Mayagüez, PR 00681-9011

(787) 832-3585

Posters:

Mangrove Ecosystem (36 by 25 inches)

Beautifully illustrated with 53 species of plants and animals

identified by scientific name in both the aerial and underwater 

sections of a typical red mangrove ecosystem (in Spanish) - $4.

Coral Reef Ecosystem (36 by 25 inches)

Beautifully illustrated with 105 species of plants and animals

typical of a Puerto Rico reef identified by scientific name (in 

Spanish) - $4.

Seagrass Ecosystem (36 by 25 inches)

Beautifully illustrates the species of plants and animals typical of a

Puerto Rico seagrass bed identified by scientific name (in Spanish)

- $4.

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Guide To The Ecological Systems Of Puerto Rico
Give Us a Chance to Live (West Indian manatee) (34 x 24 inches)

Photographic portrayal of survival problems of the endangered 

manatee. Shows feeding, with young, motorboat strikes, and coastal

development issues (in Spanish or English) - $4.

Pelagic Fish Species (22 by 34 inches)

Illustrations of seven species of open water fish found in the waters 

of Puerto Rico identified by scientific and common names (in 

Spanish or English) - $3.

Marine Turtles (27 by 34 inches)

Four marine turtles found in the waters of Puerto Rico identified by

scientific and common names (in Spanish or English) - $3.

Brochures:

Marine Turtles

This 8-panel bifold (82 by 14 inches) uses a question/answer format 

to educate the reader about sea turtles: their natural history, range,

feeding habits, why they are endangered, what is being done to 

protect them, and what individuals can do to help (in Spanish)

- Free.

The Manatee

This 8-panel bifold (82 by 14 inches) uses a question/answer format 

to educate the reader about the West Indian manatee: their natural 

history, geographic range (with a map of Puerto Rico), why they are

endangered, what is being done to protect them, and what individuals can do to help (in Spanish) - Free.

Coast and Beach Stability in the Lesser Antilles

This brochure explains and illustrates coastal beach erosion on 

tropical islands and the work being done by the coastal stabilization

project sponsored by the United Nations Educational, Science, and

Cultural Organization (UNESCO) (in English) - Free.

Fishes of Puerto Rico

This 40-page brochure is a guide to the common fish of the 

Caribbean. They are pictured and identified by scientific and 

common names. Various facts are supplied regarding size, weight, 

and food value (bilingual) - $3.

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General Technical Report IITF-35
Commonwealth of Puerto Rico

Department of Natural Resources and Environment

Department 5887

Office of Education and Publications

Muñoz Rivera Avenue, Stop 3

San Juan, PR 00906

(787) 725-8619

Poster titles:

Nature Reserves (172 by 24 inches)

A photographic collage of 23 nature reserves found throughout 

Puerto Rico and a short description of the habitats found in each 

(in Spanish) - Free.

The Marine Turtles of Puerto Rico (8 by 11 inches)

This poster uses closeup photographs to illustrate the protected sea 

turtles of Puerto Rico and provides information on life histories, 

beaches used for reproduction, and problems in their survival (in

Spanish) - Free.

Brochures:

Marine Mammals of Puerto Rico (82 by 11)

This brochure documents the whales, dolphins, and porpoises that 

can be found in the waters in the vicinity of Puerto Rico, issues 

related to their observation and avoidance, and recommendations 

for their protection. It provides information on their protection by 

the 1972 Marine Mammals Protection Act and the 1985 Puerto 

Rico Department of Natural and Environmental Resources 

regulations (17 pages in Spanish) - Free.

Please note that many of the posters and brochures described in the Puerto 

Rico Sea Grant Program and the U.S. Fish and Wildlife Service section were

cosponsored by the Department of Natural and Environmental Resources.

They may be able to supply copies if the other two agencies cannot.

U.S. Fish and Wildlife Service

Caribbean Field Office

Box 491

Boquerón, PR 00622

(787) 851-7297

(787) 833-5760

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Guide To The Ecological Systems Of Puerto Rico
Posters:

The Real Puerto Rican Toad (12 by 18 inches)

Describes the background and habitat of the endangered Puerto 

Rican crested toad and what can be done to protect the species (in

Spanish) - Free.

Tiny World Travelers (11 by 17 inches)

Describes the travels of the scarlet tanager, a Neotropical migrant 

in its summer and winter habitats. Front panel consists of illustrations and back panel provides life history information and 

teaching activities (in English) - Free.

Give Us a Chance to Live (18 by 24 inches)

Collage of photographs related to various endangered species 

(plant and animal) and their habitats - Free.

Reward (saving protected sea turtles) (11 by 14 inches)

Describes the issue of illegally killing sea turtles and the financial

reward for identification of those who do. (bilingual) - Free.

Endangered Species: The Road to Recovery (26 by 39 inches)

Illustrated collage of various U.S. endangered species (in English) 

- Free.

Endangered Means There’s Still Time (18 by 24 inches)

Collage of photographs of endangered species and habitats 

(in English).

Brochures:

Various brochures describing the Caribbean Islands National Wildlife 

Refuge system are available. These describe location, size, habitats, 

history, and wildlife species typical of each. 

This agency also provides a variety of publications describing the 

problem of endangered species in general and the status of individual

species, as well as recovery plans for the individual species.

Species in Danger of Extinction in Puerto Rico and the Virgin Islands.

This 92- by 12-inches packet of information consists of individual 

one-page descriptions of many of the endangered species in the

U.S. Virgin Islands and Puerto Rico (in Spanish) - Free.

390

General Technical Report IITF-35
National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Publications Office

7600 Sand Point Way NE

Seattle, WA 98115

(206) 526-6107

Poster:

Sea Turtles of the World (36 by 242 inches)

Illustrated presentation of the world’s sea turtles, their scientific 

and common names, short life history descriptions, and a shell key 

(in English) - $5.

This agency has many wall charts and brochures describing a variety of habitats, regional species groups, and fisheries research.

U.S. Environmental Protection Agency

Endangered Species Coordinator

Region 2

2890 Woodbridge Avenue

Building 209

Edison, NJ 08837

Poster:

Save Our Species (22 by 25 inches)

Illustrations and descriptions of a variety of U.S. endangered 

species on the front and a review of the Endangered Species Act 

and threats to species on the back (in English) - Free.

The Environmental Protection Agency has a variety of other posters and 

brochures too numerous to cite here. Request their lists for review.

National Wetlands Inventory

U.S. Fish and Wildlife Service

9720 Executive Center Drive

Suite 101, Monroe Building

St. Petersburg, FL 33702

(800) USA-MAPS (872-6277)

Poster:

Wetland Resources of the United States (40 by 66 inches)

Illustrates all the primary wetland areas of the United States and 

Puerto Rico (in English) - Free.

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Guide To The Ecological Systems Of Puerto Rico
Numerous other wetlands maps, posters, and brochures are available from: 

EPA Wetlands Information Hotline - (800) 832-7828

FAX - (703) 525-0201

e-mail - wetlands-hotline@epamail.epa.gov

Texas Partners in Flight

4200 Smith School Road

Austin, TX 78744

(512) 389-4970

Poster:

Migratory Landbirds of the Southeast: Valuable and Vulnerable (22 by 

30 inches) in color, illustrates 25 migratory landbirds, with their names

and primary habitats on the front. The back panel describes each 

species, provides scientific names, and explains why each is vulnerable 

(in English) - Free.

Ciudadanos del Karso

Urb. Las Cumbres

497 Ave. E Pol, Box 230

San Juan, PR 00926

(787) 760-2100

Posters:

El Karso Norteño

A drawing shows a partial view of the landforms (over and below

ground) of the north karst region of Puerto Rico and the human

activities negatively affecting it with written information on the 

same poster. Fifteen topics are discussed to summarize the importance of the karst region and the problems it is facing (in Spanish) 

– Free.

Los Murciélagos 

Photos of all the bat species currently found in Puerto Rico, with a

brief description of each. It has a summary in the center explaining 

the ecological importance of bats (in Spanish) - Free.

Boa

This poster shows the endemic boa species of Puerto Rico, 

Epicrates inornatus, an endangered species, and explains that they 

are not dangerous to people and are beneficial to agriculture 

(in Spanish) - Free.

392

General Technical Report IITF-35
National Geographic Society

1145 17th St., NW

Washington, DC 20036

Poster:

Coral World 

A spectacular two-sided poster, with one side a world map depicting

the location of all major coral reefs and the other side showing a 

virtual reefscape. The reefscape uses illustrations and closeup 

photography to depict coral morphology development, geography, 

reef types, communities, natural threats, human use and abuse, and 

reef conservation (in English) – Free.

Video Tapes

A multitude of video tapes are available for loan, rent, or purchase describing many

of the tropical ecosystems and the plant and animal species described in this document. The following list contains just a few titles successfully incorporated into a

college-level course in tropical ecosystems by the senior author. Should you decide

to use films to supplement classroom activities, we suggest the films be previewed

for suitability of the intended audience. Most film vendors have a free 2-week 

preview policy; you just have to request it.

Title/length Topic Source

“The Parrots Life history of the Free loan. USDA

of Luquillo” endangered Forest Service

(28 minutes) Puerto Rican parrot. Caribbean National 

Forest Río Piedras, PR 00928

“The Rain Forest” Wonders of tropical rain National Geographic Society

(60 minutes) forests in Central 1145 17th St., NW

America. Washington, DC 20036

“Tropical Rain General review of rain Finley-Holiday Film 

Forest” forests with emphasis Corporation

(40 minutes) on animals and P.O. Box 619

methods of investi- Whittier, CA 90608

gation. (800) 345-6707

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Guide To The Ecological Systems Of Puerto Rico
Title/length Topic Source

Selva Verde Reviews the animals of Nature Series

(58 minutes) the tropical rain forests Center for Public Service TV

in Costa Rica and University of North Carolina

Panama with emphasis Chapel Hill, NC

on survival adaptations (919) 962-8191

and predator-prey 

relationships.

“Hope for the Focuses on efforts to National Audubon Society

Tropics” save the tropical rain PBS Videos

(58 minutes) forests. 666 Pennsylvania Ave.

Washington, DC

(202) 547-9009

“Rain Forests— Contrasts the economic The Video Project

Proving Their values of standing rain 5332 College Ave., Suite 101

Worth” forests versus areas cut Oakland, CA 94618

(28 minutes) for timber and pasture. (415) 655-6050

“Secret World of Reviews the critical Bat Conservation International

Bats” roles that bats play in P.O. Box 162603

(58 minutes) ecosystems and Austin, TX 78716

problems produced by 

humans in the alteration of ecosystems 

and bat roosts.

“Edge of the Sea” Very good on animal Time-Life Videos

(30 minutes) adaptations and David Attenborough

feeding, and as an Living Planet Series

introduction to mangroves and sea turtles

—organisms that live 

at the edge of the sea.

“Creatures of the Excellent review of National Geographic Society

Mangroves” mangrove ecosystems 1145 17th St., NW

(60 minutes) and plant and animal Washington, DC 20036

adaptations.

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General Technical Report IITF-35
Title/length Topic Source

“Margins of the ” Good review of the Time-Life Films

Land ecology of mangrove Living Planet Series

(55 minutes) swamps. Available from:

North Carolina Film Library

Audio Visual Branch

1811 Capital Blvd.

Raleigh, NC 27635

(919) 733-4376

“Treasures of the Underwater review of NOVA

Great Barrier Reef” the Great Barrier WQBH Video

(60 minutes) Reef’s ecology. A P.O. Box 2284

variety of animal South Burlington, VT 05407

species are reviewed (800) 255-9424

and coral reproduction 

is highlighted.

“Cities of Coral” Good review of Educational Video Network

(60 minutes) corals and the com- 1401 19th St.

plexities of coral reefs. Huntsville, TX 77340

(409) 295-5767

“Perils of Excellent review of Bullfrog Films

Plectropomus” the life and death P.O. Box 149

(56 minutes) struggles of fish on a Oley, PA 19547

coral reef, with special (800) 543-3764

reference to fishing 

pressures produced by 

humans.

“Jewels of the Review of coral reef Teacher’s Video Co. 

Caribbean” species of the P.O. Box 4455

(60 minutes) Caribbean region. Scottsdale, AZ 85261

(800) 262-8837

“Ecology of the Reviews general Man and the Biosphere

Coral Reef” ecology and the decline Series–Films for the

(23 minutes) of coral reefs and their Humanities and Sciences

inhabitants. Box 2053

Princeton, NJ 08543

(800) 257-5126

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Guide To The Ecological Systems Of Puerto Rico
Sources of Maps and Visitor Guides to Puerto Rico

Individuals or groups planning to spend time in various parts of Puerto Rico will 

need maps that will help them locate destinations of interest. The following lists

sources of free maps and detailed destination guides, as well as sources of maps

that must be purchased. Multiple copy requests should be ordered at least 6 weeks

in advance. There may be handling and postage charges for group orders. Most of

the visitor publications will be available at tourist centers throughout the island,

San Juan’s international airport, and car rental offices. Detailed street maps are

essential for travel in old and new San Juan. When traveling to old San Juan, it is

wise to consider using the public bus system (guaguas or autobus) because of limited parking. All fares on the regular buses are 75¢. The express bus is $1 between

the main bus terminals. You will need quarters because the drivers do not make

change. The buses are new, air conditioned, and will drop you at the bus terminal

across from the cruise ship docks where you can jump on the free trolley that will

take you through Old San Juan. All bus stops have green and white street signs that

say Parada. Each stop has signposts that indicate which bus numbers stop there.

The bus stop going the opposite direction will normally be across the street.

Free Terrestrial Maps and Guides

➢ “Metropolitan San Juan”—Bus System Map

Route map to the Metropolitan Autobus System (AMA)

Department of Transportation and Public Work

P.O. Box 3909 (These are available at the main

San Juan, PR terminal buildings.)

Tel: (787) 767-7979

➢ “Puerto Rico Travel Map”—Map illustrates locations of major environmental

and recreation sites. This map has good detail, with regional blowup maps.

Puerto Rico Convention Bureau

255 Recinto Sur

Old San Juan, PR 00901

Tel: (787) 725-2110

Fax: (787) 725-2133

➢ Street map of Old San Juan

Puerto Rico Tourism Company

Tel: 1-800-866-STAR

Tel: (787) 721-2400

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General Technical Report IITF-35
➢ Official guide to Puerto Rico - ¡Qué Pasa!

This magazine is published six times a year. It provides the most complete

review of “what is happening” throughout the island. It generally runs over 

100 pages in length and includes everything from island history, a 60-day 

calendar of events, walking tours, location of medical facilities, a variety of

maps, shopping, restaurants and hotel, and a breakdown of what to see and 

do in nine regions of the island.

Puerto Rico Tourism Company

¡Qué Pasa! Magazine

P.O. Box 6338

Loíza Street Station

San Juan, PR 00914

Tel: (787) 728-3000

Tel: (787) 268-0135

E-mail:quepasa@casiano.com

➢ “Puerto Rico Travel and Sport Planner”

This is an annual publication that highlights all the main attractions, with 

special emphasis on ecotourism, sports, and recreation opportunities in 

various regions of Puerto Rico. It features regional maps, Paradores

housing locations, and addresses and phone numbers of recreation sites. 

This is particularly useful for hikers, divers, sea kayakers, beach enthusiasts,

and golfers.

Information Center

Puerto Rico Tourism Company

La Casita

P.O. Box 9023960

San Juan, PR 00902-3960

1-800-866-STAR

Tel: (787) 721-2400

Fax: (787) 722-5208

➢ “Places to Go”

This is an annual publication that highlights hotels, restaurants, bars, 

and regional tourist attractions.

Puerto Rico Tourism Company

(787) 729-9060

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Guide To The Ecological Systems Of Puerto Rico
Products of the Puerto Rico Tourism Company will be sent to you by contacting their address or phone above. The information center sends out single copies.

For multiple copies, requests have to be made to the publishers of the publications,

and there may be a charge.

➢ “Puerto Rico Road Map”

The Puerto Rico Department of Transportation and Public Works Authority 

will provide a detailed roadmap with full coverage of the island, greater 

San Juan, and the island’s other major cities. It has street locators and a 

distance chart.

Roads Authority

Department of Transportation

P.O. Box 3909

San Juan, PR

Tel: (787) 767-7979

The above map can be obtained commercially from:

Gousha Travel Publications

PO Box 49006

San Jose, CA 95161-9006

Tel: (408) 296-1060

Terrestrial and Marine Maps Available for Purchase

Two additional maps that will prove useful are the USDA Forest Service maps 

of the Caribbean National Forest.

➢ “Maps of the Caribbean National Forest”

This map has two versions. One is a small pocket-size multifold, the 

other is a very large wall map. This map includes locations of the trails 

in the El Yunque recreation area of the forest. They can be purchased at 

the El Portal Visitor Center as you enter the forest or can be ordered by

contacting:

Caribbean National Forest

El Yunque Ranger District

P.O. Box B

Palmer, PR 00721

Tel: (787) 887-2875

Other specialty maps you may find useful are:

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General Technical Report IITF-35
➢ Topographic 7.5 Quandrangle Map

El Yunque, Puerto Rico

Sold by: U.S. Geological Survey

Federal Map Distribution Center

Box 25286

Denver, CO 80225

or:

Department of Public Works

San Juan, PR 00910

➢ Parguera Quadrangle, Puerto Rico

7.5 minute series (topographic)

Sold by: U.S. Geological Survey

Federal Map Distribution Center

Box 25286

Denver, CO 80225

or:

Department of Public Works

San Juan, PR 00910

(Very good for coral reef and mangrove swamp positions and water depths.)

➢ West Coast of Puerto Rico

Coastal and Geodetic Survey Map 901

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

Map Distribution Center

6501 Lafayette Ave.

Riverdale, MD 20737

(301) 436-6990

(Very good for review of terrestrial altitudes and marine depths for the entire

west end of Puerto Rico, including Mona and Desecheo Islands; all reefs are

shown and depths are expressed in fathoms.)

➢ East Coast of Puerto Rico—Virgin Passage and Sonda de Vieques

Coastal and Geodetic Survey Map 904

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

Map Distribution Center

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Guide To The Ecological Systems Of Puerto Rico
6501 Lafayette Ave.

Riverdale, MD 20737

(301) 436-6990

(Excellent for all of eastern Puerto Rico, Culebra, Vieques, associated small

islands and reefs all the way to St. Thomas, Virgin Islands; all depths are

expressed in fathoms.)

Governmental Organizations

Commonwealth of Puerto Rico

Department of Natural and

Environmental Resources (787) 724-8774

Marine Resources (787) 725-8619

Reserve and Refuges (787) 724-2816

Terrestrial Resources (787) 722-7517

Las Cabezas de San Juan Nature (787) 722-5882

Reserve–Fajardo

Boquerón Wildlife Refuge–Boquerón (787) 851-4795

Guánica Forest Education Center–Guánica (787) 821-5707

Tropical Botanical Garden–Río Piedras (787) 763-4408

Institute for Tropical Ecosystem Studies (787) 764-0000 

Ext. 2866

Environmental Quality Board (787) 767-8181

University Sea Grant Program (787) 832-3585

Puerto Rico Water Resources Authority (787) 620-2277

U.S. federal

U.S. Department of Agriculture (USDA) (787) 729-6872

USDA Forest Service

International Institute of Tropical (787) 766-5335

Forestry

Caribbean National Forest (787) 888-1880

El Yunque Ranger District (787) 887-2875

El Portal Education Center (787) 888-1880

U.S. Environmental Protection Agency

Caribbean Field Office (787) 729-6951

San Juan Bay National Estuary (787) 725-8164

Program

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General Technical Report IITF-35
U.S. Department of the Interior 

Fish and Wildlife Service (787) 749-4338

U.S. Geological Survey (787) 749-4346

Marine Geology Division (787) 729-6934

Water Resources Division (787) 749-4346

National Park Service (787) 729-6777

Cabo Rojo National Wildlife Refuge (787) 851-7297

Environmental Education Office Ext. 29

Caribbean Islands National Wildlife Refuge (787) 851-7258

National Oceanic and Atmospheric (787) 253-4586

Administration 

Natural Resource Conservation Service (787) 766-5987

U.S. Army Corps of Engineers (787) 753-4996

(787) 753-4974

Nongovernmental Organizations 

Conservation Trust of Puerto Rico Own and/or manage 14 natural and 

P.O. Box 9023554 historic properties on the island

San Juan, PR 00902-3554

Tel: (787) 722-5834

Fax: (787) 722-5872

E-mail: fideicomiso@fideicomiso.org

Citizens for the Karst Specializes in limestone region

497 Ave. E Pol conservation and research; owns

Box 230 nature reserves in the karst region

San Juan, PR 00926-5636

Tel: (787) 760-2100

Fax: (787) 760-2070

E-mail: enlacepr@caribe.net

Foundation for the Plains Pigeon Project Ecology and conservation of 

University of Puerto Rico endangered Puerto Rican plain 

P.O. Box CUH pigeon

Department of Biology

Humacao, PR 00791-4300

Tel: (787) 850-9331

Fax: (787) 850-9417

E-mail: plainpigeon@hotmail.com

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Guide To The Ecological Systems Of Puerto Rico
Guardians of the Mountains Promotes nature tours and a new

P.O. Box 425 mountain reserve

Ciales, PR 00638

Tel: (787) 858-9057

E-mail: www.guardianes.org

Herpetological Society of Puerto Rico Principal herpetology society,

Metropolitan University promotes conservation of reptiles 

P.O. Box 21150 and amphibians and their 

San Juan, PR 00928-1150 habitats throughout Puerto Rico

Tel: (787) 766-1717 Ext. 6464

Fax: (787) 759-7663

E-mail: um_mortiz@suagm4.suagm.edu

Industrial Mission of Puerto Rico* Very active grassroots 

P.O. Box 363728 environmental action group

San Juan PR 00936-3728 (*The name does not imply any 

Tel: (787) 765-4303 connection to Puerto Rico’s 

Fax: (787) 754-6462 industries.)

Natural History Society of Puerto Rico One of the older citizen-based

P.O. Box 361036 environmental awareness 

San Juan, PR 00936-1036 groups

Tel: (787) 723-8915

Fax: (787) 268-8872

E-mail: f.ferrer@uscac1.usc.clu.edu

Network of Caribbean Marine Mammal Marine mammal conservation 

Strandings and research

P.O. Box 38030

San Juan, PR 00937-1030

Tel/Fax: (787) 767-8009

E-mail: rcv@caribe.net

Ornithological Society of Puerto Rico Main birders group

P.O. Box 1112

Ciales, PR 00638-1112

E-mail: tody@coqui.net

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Speleological Society of Puerto Rico Offers cave explorations and

P.O. Box 31074 information about tour companies

San Juan, PR 00929-1074 specializing in cave and sinkhole

Fax: (787) 783-4566 tours

Puerto Rican Conservation Foundation Mainly research; runs an annual

382 Ave. San Claudio environmental Biodiversity Week 

in PMB 97 various areas of the island; 

San Juan, PR 00926-9910 publishes the 83-page “Directory 

Tel: (787) 760-2115 of NGO’s in Puerto Rico”—

Fax: (787) 761-3889 $13 (plus handling $5)

E-mail: fconserv@tld.net

Puerto Rican Environmental Alliance Umbrella group for various 

497 Ave. E Pol environmental and ecology

Box 230 organizations of Puerto Rico

San Juan, PR 00926-5636

Tel: (787) 760-2100

Fax: (787) 760-2070

E-mail: enlacepr@caribe.net

World Wildlife Fund (WWF) Protection of the world’s wildlife

Tel: (787) 753-7694

Conserva el Encanto Promotes litter control and island

(Keep Puerto Rico Beautiful) beautification projects

Mr. Jaime Pabon

Tel: (787) 758-2242

Waterkeepers of Puerto Rico Monitor and prosecute

Mr. Ricardo de Soto violation of environment laws in

Tel: (787) 630-7590 Puerto Rico’s watersheds

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Glossary

achene—Dry indehiscent fruit formed from one carpel, with one seed 

not fused to the fruit wall.

acute—Leaf blade apex ending in a sharp point.

acuminate—Leaf blade apex ending in a tapered point.

adaptation—A feature of structure, physiology, or behavior that promotes the likelihood of an organism’s survival and reproduction in a particular environment.

adventitious—Roots having their origin in stem tissue, such as a stilt root.

aerenchyma—Parenchyma tissue with large intercellular spaces for air storage, 

well developed in aquatic and wetland plants.

aggregate (plant fruit)—Fruit formed from the fusion of multiple pistils in one 

flower, as in raspberry.

aggregate (mineral)—Any of several hard inert materials (sands, gravel, slag) often 

used in road construction or manufacturing cement.

agroforestry—Planting of trees and crops together; a system that hosts higher 

biodiversity than monocultures.

agroecosystem—Mixed system of agriculturally important plants designed to create

beneficial habitat for native species and/or migratory species, such as

Neotropical migrant birds.

algae—Major division of the plant kingdom consisting of simple nonvascular 

photosynthetic plants, normally fresh or marine aquatic.

alien (species)—A species accidentally or intentionally introduced into a new 

territory. May also be referred to as exotic or introduced species.

allochthonous—Material imported into an ecosystem from outside.

alluvial—Deposits of material associated with a stream.

alternate—Arrangement of leaves or branches whereby they occur at different 

levels on opposite sides.

ambiente—Spanish term for environment.

amensalism—Relationship in which one organism affects another organism, but is 

not affected in return.

amphibian—A member of the vertebrate class Amphibia, which includes frogs, 

toads, and salamanders.

amplexus—Male/female locking position for exchange of sperm.

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anaerobic—Environmental condition of no oxygen. 

angiosperm(ae)—Major group of plants referred to as the flowering plants that 

produce fruits and seeds.

anthropogenic—Human related, produced, or caused.

apex—Tip of a leaf, stem, or branch.

apical meristem—A group of cells at the growing tip of a shoot or root which, 

through continuous cell division, forms new plant tissue.

aquifer—Porous rock or permeable unconsolidated material capable of storing or 

producing water.

aspect—Position facing a particular direction, such as on the side of a mountain.

atoll—A coral reef surrounding a central lagoon resulting from a drowned volcanic 

cone.

avifauna—A group of birds existing in a particular region.

bagasse—Leftover organic residue resulting from the crushing of sugar cane stems.

bank reef—An offshore reef formed along a wave cut platform in the Caribbean.

barrier reef—An offshore coral reef running parallel to shore and separated by a 

lagoon from the shore; for example, barrier reef formed in association with a 

continental land mass such as the Great Barrier Reef of Australia.

bateyes—A section of an indigenous ceremonial park used for games.

bay—Part of an ocean partly enclosed by land, such as the Bay of San Juan.

benthic—Living or growing attached to the bottom of a body of water.

benthos—the bottom of the sea or lake.

bicameral (legislature)—Form of representative government consisting of two 

houses or legislative chambers.

biodiversity—The genetic, species, and ecological diversity of life in a given area.

bioluminescence (bioluminescent)—Production of light by living organisms.

biomass—Total weight of organisms per unit area.

bleaching—Active loss of endosymbiotic algae from coral tissue resulting in 

whitening of the polyps and the colony.

bog—A poorly drained wetland area, normally with acidic, spongy ground made of 

undecomposed organic plant matter.

bole—Another name for tree trunk.

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brackish—Water containing salt at levels lower than pure sea water.

buttress(ing)—Arched roots originating in the base of a tree trunk extending away 

from the base and functioning as support for the tree.

buttress zone—Region of a coral reef dominated by large mounds of boulder coral, 

generally seaward and deeper than the Acropora zone.

bycatch—Incidental capture of nontarget sea organisms, for example, netting of 

fish while shrimping.

canopy—Top layer of a forest or individual tree.

capsule—A dehiscent fruit with more than two chambers.

Caribs—Fierce Caribbean tribe located in the Lesser Antilles that raided Taíno

villages and fought Spanish conquistadores.

carpel—Female part of a plant flower.

cartón—Material produced by termites that makes up their mounds and tunnels.

caste—Functional status of a social insect such as worker or soldier.

catadromous—Organisms that live in fresh water, but migrate to salt water to lay 

their eggs, such as eels.

cauliflory—Flowers with their origin in the leafless bole of a tree such as cacao.

charismatic species—Attributed to a wild species with a quality of special appeal 

such as large mammals (bears, elephants, cats, gorillas) that elicits popular 

support for their survival.

chevron—Body marking looking like a pair of stripes meeting at an angle.

chlorenchyma—Chlorophyll-bearing tissue.

chlorosis—Absence or death of green pigments in plants, for example, produced by

salt exposure.

CITES—Convention on International Trade in Endangered Species.

cleaning station—The place where cleaning symbiosis occurs.

cleaning symbiosis—Action whereby two different organisms gain benefit from a 

cleaning behavior, that is, fish have their ectoparasites removed and cleaner

organisms (shrimp, fish) gain access to food.

climax—A stable balanced community, the end of succession.

clone—An individual or group of individuals propagated from an identical 

progenitor by vegetative means.

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cloud forest—Tropical mountain forests that are shrouded in clouds for much of 

the day, often showing profuse epiphytic growth.

clutch size—The number of eggs laid in a nest.

cnidaria—Animal phylum that includes hydras, jellyfish, sea anemones, and corals.

cnidoblast—A specialized cell giving rise to a nematocyst.

coelenterates—radially symmetrical animals having saclike bodies with only one 

opening and tentacles with stinging structures; they occur in polyp and medusa.

coelenteron—The body cavity of coelenterates.

commensalism—Relationship between two organisms in which one lives on or in 

another species that is not harmed or benefited. 

community—A defined group of plants and/or animals distinguishable from other 

assemblages.

compound—A fruit composed of multiple pistils in one flower.

conservation—A resource management ethic that balances proper husbanding of 

resources and their use for the benefit of people.

convergent evolution—Process whereby natural selection and adaptation cause 

unrelated organisms to look and act very much alike, for example, cacti and

euphorbs.

coppice (coppicing)—A thicket of small trees or the process of harvesting tree and 

shrub stems for firewood through a series of harvest cuts.

coqui—Generic reference to a genus of frogs (Eleutherodactylus) found throughout 

Puerto Rico.

coral—Colonial marine animals with endosymbiotic algae of the classes Anthozoa 

and Hydrozoa, grouped as stony or soft coral based on carbonate versus protein

exoskeletons.

coralline algae—Algae that precipitate a layer of calcium carbonate, thus making 

them appear coral-like, for example, Halimeda spp.

coral dieback—Death to segments of previously healthy coral colonies related to 

disease or bleaching events.

coral reef—Complex plant and animal communities forming one of the most 

productive marine ecosystems in the Earth’s tropical zone.

coriaceous—Leathery in appearance.

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cotyledons—leaf of the embryo of a seed plant, which upon germination either 

remains in the seed or emerges, enlarges, and becomes green. Also called seed

leaf.

crown—Top layer of a tree.

cutting—Process whereby woody shrub and tree stem growth is harvested by 

machete or saw for local use.

cuttings—Asexual propagation of plants achieved by cutting sections from a 

mature plant and planting them.

cyme—An inflorescence in which flowering begins in the middle and progresses 

toward the periphery.

deciduous—Falling of leaves at end of growing season or onset of drought.

dehiscent—A fruit type that breaks open at maturity.

depauperate—Reduced as in numbers of organisms per unit of area or size of 

individuals.

detritus—Loose organic material that collects from the disintegration of dead 

organisms or their wastes.

dicotyledons—The class of angiosperms having an embryo with two cotyledons or 

seed leaves.

diffusion—Physical process of equalization, for example, movement of gases from 

high concentration to lower concentration.

dinoflagellates—Members of the division Pyrrophyta, mostly marine, singlecelled; so called “fire algae” because many are bioluminescent.

dioecious—Having separate sexed male and female flowers on different 

individuals.

diurnal—Active or opening during the daytime.

domesticated—Animals or plants that have been selected and bred for human use.

dorsolateral—Running down the side.

drop roots—Adventitious roots originating in tree branches.

drupe—Fleshy fruit with one or more seeds, for example, plum or mango.

duff—Accumulated dry organic matter on the top layer of soil.

ecological services—Ecological systems and species provide vast service functions 

to life systems by performing processes such as cleaning contaminated water

and air, pollination, seed vectoring, and decomposition of organic matter.

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ecosystem—Biotic community of different species interacting with one another 

and with the chemical and physical factors making up the abiotic environment.

ecosystem management—The blending of the needs of people and environmental 

values in a way that will promote a biologically diverse, healthy, productive,

and sustainable ecosystem.

ecotone—A transitional area between different habitats or communities.

ecotourism (ecotourist)—Tourism or tourist that emphazes special features of the 

natural world, for example, wildlife or special habitats.

edaphic—Biologic or ecologic conditions of the soil.

edge effect—A change in species and physical conditions at the boundary between 

two ecosystems.

effluent—Any substance, such as a liquid industrial waste or sewage, which enters 

the environment from a point source (pipe).

elfin forest—Short scrubby forest found growing in extreme conditions such as 

windy rainswept mountain ridges

elliptic—Widest in the middle with equal tapering at both ends of a leaf.

El Niño—Spanish for “Christ Child”; phenomenon that often occurs near 

Christmas whereby ocean waters off Ecuador and Perú warm. This results in

the disappearance of anchovy schools and produces changes in the jet stream

resulting in heavy storms and rains over California and the Midwestern United

States.

emergent—A wetland plant growing at the edge of a lake, river, or bay where it is 

constantly moist, such as cattails (Typha) in a marsh.

emergent tree—Tall tree growing above the normal canopy of a forest.

endangered species—Wild species with so few survivors that the species could 

become extinct in most of its range.

endemic—Restricted to a certain geographic area or habitat.

endosymbiotic—A symbiotic relationship where one organism lives inside the cell 

of another, for example, coral and zooxanthellic algae.

endozoic—Living inside an animal.

Eocene—The second of five epochs in the tertiary period of geologic time 

approximately 54.9 to 3 million years ago.

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epibionts—Organism that lives on the exterior of another, but does not feed on the 

host; may be plant or animal.

epifauna—Animals that live on the benthos or organisms attached to or moving 

over it.

epiphyte (ephiphytic)—Plants that live on the surface of other plants, but do not 

derive nourishment from the host.

estuarine—Associated with an estuary where a river enters the intertidal zone of 

the ocean or the general wetland types that develop there.

eutrophic—A condition in water that is nutrient-rich and supports a high level of 

biological productivity.

eutrophication—The process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates, which can stimulate excessive growth of aquatic plants, especially algae, and this reduces dissolved 

oxygen.

exotic species—Species that is nonnative, that is, that migrates or is introduced into 

an ecosystem by humans.

extinction—Disappearance of a species. It can be at the local or regional population level, or the world for the entire species.

facultative—Ability to live under a variety of conditions, for example, may prefer 

wet habitats, but can live in a upland setting; or may develop a trait occasionally, but not all the time, as in the case of white mangroves producing pneumatophores.

fallow—Land no longer being used for crop production.

family—A group of closely related organisms ranking above genus, designated by 

the ending “aceae” such as Fabaceae, the legume family.

fauna—All animals present in a given region.

feral—Domesticated animal that has reverted back to the wild, such as dogs or pigs.

field capacity—The maximum amount of water a soil can hold against gravitational

forces.

floating-leaved—A wetland plant with floating leaves at the surface, but attached 

to bottom sediments in a lake, such as water lily (Nymphaea odorata).

flora—All plants present in a given region.

follicle—A plant fruit type that opens along one suture, typical of the milkweeds.

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Fomento—Called “Operation Bootstrap”; it was an economic development 

program started in 1950 to promote real estate development, expanded use of

ports, and industrial and tourism investment and promotion in Puerto Rico.

food chain—The passage of energy and materials from producers through a 

sequence of herbivores and/or carnivores.

food web—A group of interrelated food chains.

forbs—Nonwoody plants with broad leaves.

forereef—The slope on the seaward side of a reef that is constantly exposed to 

waves and currents.

fouling community—Dense growth of organisms on solid surfaces such as boat 

bottoms and pipes, or red mangrove roots that may interfere with normal 

operation of either.

fragmentation—Division of habitats into small sections that can produce changes 

in available territory and reproductive success for sensitive species.

free-floating—A wetland plant floating freely on the water’s surface such as duck

weed (Lemna minor).

fringing forest—Forest located along an ecotone such as mangroves at the intersect 

between water and land.

fringing reef—A coral reef contiguous with the coast, but lacking a lagoon.

frond—Special term for the leaf of a fern or palm tree; also applied to the leaflike thallus of marine algae.

frugivore (Frugivorous)—Fruit eater.

fungi—Lower organisms that produce spores, hyphal vegetative structures, and are 

nonphotosynthetic.

GDP (gross domestic product)—Total market value of goods and services produced 

within a country during a specific period and which does not include activities

of offshore corporations.

genetic bottleneck effect—The result of the loss of genetic diversity when a 

population experiences a severe reduction in effective population size.

genome—All of the genetic material in one organism.

genus (Genera)—A group of closely related organisms, below family, usually 

consisting of more than one species. First Latinized word in a scientific name

such as Ceiba pentandra.

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global climate change—Changes in the climate of the Earth. Opinions differ as to 

the effect of anthropogenic processes such as burning and the release of carbon

dioxide (CO2), methane (CH4), chlorofluorocarbons, and so forth.

globose—spherical.

gneiss—A foliated or layered metamorphic rock such as granite.

GNP (gross national product)—Total market value of all goods and services 

produced by a nation’s economy during a specific period.

grazer (grazing)—An organism that feeds on live vegetation or animal growth such 

as cow on grass, or parrot fish on coral.

Greater Antilles—Four largest islands of the West Indies: Cuba, Hispaniola, 

Jamaica, Puerto Rico.

greenway—A transportation or urban trail corridor area used for recreation that 

emphasizes natural features associated with a park or river area; it is a soft

development zone in an otherwise urban setting.

gymnosperm(ae)—Major group of plants that produce naked seeds borne on seed 

leaves such as pines.

habitat—The place or environment in which an organism lives, that is, its home.

hair(y)—Any epidermal outgrowth that covers or protects an organism’s outer 

surface.

halophyte (halophytic)—A plant capable of thriving in salt water or saline soils; 

a shore plant.

hard coral—Those coral species that secrete a hard calcium carbonate skeleton.

haystack hill—Hills that resemble a rounded haystack typical of karst regions.

hepatics—The general term for the class of bryophytes that contains liverworts.

herb(aceous)—Nonwoody seed plant.

herbaceous productivity—Biomass created in a given area by the herb layer of the 

community.

herbivorous (herbivore)—Animal that feeds on herbaceous plants.

hermatypic coral—Corals involved in reef building such as Diploria (brain), 

Montastrea (star) and Acropora (horned).

homeostasis—Dynamic equilibrium or steady state in a species or ecosystem.

horticulture—Practice of growing and using plants for human use, such as in 

gardening and landscape beautification.

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host—An organism that supplies nourishment, provides protection, or a place to 

reside.

hotspot (biodiversity)—An area of unusually high species diversity or endemics.

hurricane—Violent oceanic generated tropical storm with winds greater than 120 

kilometers per hour (75 miles per hour).

hydrocoral—Fire coral (Millepora); likely to produce skin reactions upon exposure.

hypersaline—Very high salt content.

igneous—The result of extreme heat; silicate minerals formed by the cooling and 

solidification of magma.

indehiscent—Fruit that does not split open at maturity.

inflorescence—A flowering stem with multiple flowers often branched.

insect—A large class of animal without vertebrae, with three sets of legs and two 

pairs of wings. Nearly 1 million species are known.

insectivore (Insectivorous)—An organism that preys on insects as a food source.

insular shelf—A shallow underwater ledge or extension of the sublittoral coastline 

around an island, similar to a continental shelf.

interference competition—When an organism competes with another for space, 

light, or nutrients and one has an ability to grow under low light or other

altered habitat conditions, and as a result outcompetes the other.

interspecific—Between distinct species.

intraspecific—Within a species.

introduced species—Not native, having been brought into a country or introduced 

into an ecosystem by humans.

invertebrate—Animals without backbones such as insects.

karst—Irregular topography developed by the action of surface and underground 

water on soluble rock such as limestone and characterized by sinkholes,

haystack hills, streamless valleys, underground rivers and caves.

keystone species—Species that play dominant roles in an ecosystem and affect 

other organisms beyond their own abundance or biomass, for example, bats as

pollinators and seed vectors.

lacunae—Large air spaces between cells like those found in aquatic plants.

lacustrine—Related to a lake or wetland associated with a lake.

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lagoon—A protected shallow body of water, such as on the leeward side of a coral 

reef or the inner water section of an atoll.

lanceolate—Shaped like a lance.

lateral root—Moving out sideways away from the center of the plant.

leaching—Washing of ions out of soil, organisms, or plant surfaces.

leaflets—A leaf blade is divided into distinct units, that is, there is not one distinct 

simple blade.

leeward—Away from the direction the wind is blowing.

legume—Fruit type of the plant family of Fabaceae; fruit that breaks open along 

two sides such as in flamboyán.

lenticel—Air exchange pore in periderm of stems and roots.

Lesser Antilles—A long arc of small islands in the eastern Caribbean Sea extending 

from Puerto Rico to the north coast of Venezuela. 

liana—Woody climbing vine of tropical forests.

limestone—A sedimentary rock composed largely of calcium carbonate (CaCO3), 

which can be formed by organic or inorganic processes. Many islands in the

Caribbean have extensive limestone beds owing to formative activities of

marine organisms such as coral and algae.

litter—Partly decomposed plant residues on the surface of soil.

littoral—Growing at or near the seashore; zone between high tide and low tide.

macrobenthic—Macroscopic organisms growing attached in the benthic zone of a 

water body, seagrasses, for example.

macrophyllous—Having large leaves.

mammal—A class of warmblooded vertebrates that gets its name from the 

mammary glands used for feeding their young.

mangrove—A generic term applied to many species of tropical plants that can grow 

with their roots partly or completely submerged in sea water or that make up

tidal, riverine, and basin forests in the tropics.

mariculture—The application of the principles of agriculture to the commercial 

production of marine organisms.

marine—Having to do with oceanic processes, saltwater conditions, or organisms 

found in marine habitats.

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marine fishery reserves—Special areas of the ocean, coral reefs, and estuaries 

where no or limited use of marine resources is permitted.

marsh—A wetland without trees, dominated by grasses, sedges, rushes, and other 

herbaceous groups.

mass wasting—Downslope movement of earth materials.

medusa—Free-swimming, bell-shaped stage in a cnidarian life cycle.

meiotic—Reductional division of chromosomes whereby the number is reduced 

by half.

mesophyllous—Having leaves of moderate size, between microphyllous and 

macrophyllous.

metabolites—Material produced by metabolism, which is all of the chemical and 

physical activities necessary to sustain an organism.

metamorphic—Changed rock, that is, any rock that has been changed in texture 

or composition by heat, pressure, or chemically after its original formation.

microphyllous—Having small leaves.

migratory—Changing habitat according to season, climate, or food supply. For 

example, movement of Neotropical birds from North America south to the

tropical latitudes during the temperate winter.

Miocene—Geologic period between the Oligocene and Pliocene, approximately 

7 to 26 million years ago.

mitigation—To create, restore, or preserve other wetlands in exchange for permission to alter preexisting natural wetland associated with a development project,

such as a road or building.

monocotyledons—The class of angiosperms having an embryo with only one 

cotyledon or seed leaf.

monoculture—An agriculture system that grows one crop over an extended area 

and period.

monoecious—Having the male and female flowers on the same plant.

monogeneric—A plant family composed of only one genus.

monospecific—A taxonomic or ecological unit with one species.

morphology (morphological)—The form or structure of a plant or animal.

multiple fruit—A fleshy fruit formed from several to many separate flowers in a 

tight inflorescence such as pineapples.

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mutualism—A mutually benefical relation between two organisms, in some cases 

one may not be able to live without the other.

nape—Neck area.

native species—Species that normally live and thrive in a particular location.

naturalized species—An introduced species that over time was able to acclimate to 

the new conditions and now grows and sexually reproduces like an indigenous

species without the aid of people.

nematocyst—A stinging cell of cnidarian coelenterates such as coral and related 

groups used for protection and obtaining prey.

Neotropical—New World tropics and subtropics roughly corresponding to 25° 

north and south of the equator.

neutralism—The lack of any effect on either organism in a coexisting relationship.

NGO—Nongovernmental organization.

niche (ecological)—Total way of life or role of a species in an ecosystem including 

all physical, chemical, and biological conditions a species requires to live and

reproduce.

nocturnal—Active or opening during the night time.

node—Place on a stem at which leaves or branches arise.

nut(let)—Dry, indehiscent fruit with a hard woody fruit wall; nutlet is a very small 

nut-like fruit.

obligate—An organism restricted to a habitat where certain conditions are almost 

always present.

oblique—Refers to the base of a leaf blade where the two sides do not join at the 

same position on the petiole; that is, one side is lower.

obtuse—Slightly angled leaf apex.

octocoral—Seafans, and seawhips that exhibit polyps with eight tentacles.

odd-pinnately compound—Plant leaf composed of an odd number of leaflets.

old growth—Pertaining to forests or other ecosystems that have not been cut or 

altered for centuries.

Oligocene—Geologic period between the Miocene and Eocene, approximately 

26 to 38 million years ago.

oligotrophic—Water containing few nutrients resulting in low productivity.

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opposite—Leaves or branches are attached at the same level on a stem or node.

orbicular—Round in shape.

orographic rain shadow—Having to do with mountains whereby rain shadows are 

produced on the downwind side of a mountain after moisture-laden clouds

release their water on the windward side.

pallid—Background colors of light brown, cream, or green.

palmately compound—Plant leaf composed of multiple leaflets attached in the 

form of the human hand.

palustrine—Nontidal wetlands not confined by channels and not marginal to lakes.

panicle—A branched complex raceme inflorescence.

pantropical—Throughout the Earth’s tropical zone.

parenchyma—The basic cell type of higher plants, found in tissues such as stem 

pith, fruit pulp, and leaves and used primarily for storage.

parthenocarpic—The formation and growth of fruit without fertilization and thus 

without production of viable seeds.

patch reef—A coral boulder complex or clump of corals not attached to a major 

reef.

peduncle—The main flower-bearing stem of a plant.

pelagic—Living in open water.

periderm—The outer layer of protective tissue of a plant.

persistent—Remaining attached through or after maturation.

petal—Part of the flower that is usually colorful; collectively called the corolla.

petiole—Part of a leaf that attaches a leaf blade to a stem.

petroglyph—A carving on a rock.

phase shift—Changes in one or more species populations produced by predation, 

disease, or pollution. The organisms that previously were structural dominants

in an ecosystem are replaced by different organisms, for example, macro algae

replacing coral as a result of overharvesting of herbivorous fish.

pheromone—Chemical substance produced by an individual that can influence the 

behavior of others of its species, such as mating, feeding, or reaction to danger.

phosphorescence—Release of light caused by prior absorption of energy and continuing release of light energy for a time after the energy source has stopped.

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phreatophyte—A plant capable of sending roots deep into the ground to obtain 

water; sometimes called well plants.

phylum(la)—The major division representing a separate evolutionary line within 

the animal kingdom.

phytogeography—Study of the geographic distribution of plant species, communities, or ecosystems.

phytoplankton—Single-celled algae from various divisions; characterized by sinkholes, haystack hills, streamless valleys, underground rivers and caves.

pinnately compound—Leaf blade that is divided into leaflets and arranged with the 

leaflets on each side of a midrib. If there is an even number of leaflets, the

condition is referred to as even pinnately compound versus odd pinnately 

compound.

pliocene—The last of five epochs in the tertiary period of geologic time; 5 to 2 

million years ago.

pneumatophores—Aeration roots growing upward from the horizontal roots of 

black mangroves.

pollen—Microscopic meiotic product of anthers that carry the male sex cell to the 

female flower part (pistil) prior to fertilization.

pollinator—An organism that provides a vehicle for the transfer of pollen in the 

process called pollination.

polyculture—Raising of a variety of crops in a small area, whereby the plants are 

less susceptible to disease and insect pest.

polymorphic—Variable body forms in the life history of an organism.

polyp—One of the individuals making up a colonial animal such as coral; very 

simple animals lacking organs, possessing tentacles.

population—A group of individuals of a species living in a certain area.

predator—An organism of one species that captures and feeds on parts or all of 

another organism of a different species (prey).

prescribed fire—A fire that is intentionally set in order to reduce the threat of a 

wildfire, produce better pasturage, or control unwanted species.

preservation—To protect and keep resources from being destroyed, that is, the 

keeping of nature for nature’s sake regardless of its usefulness.

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preserve—An area restricted for the protection and preservation of the natural 

resources, including plants and animals within its boundaries; frequently

defined as a non-use area for extraction purposes.

primary species (forest)—The species or forest typical of an area at its mature or 

climax stage.

primary productivity—The rate at which energy is stored in an ecosystem via 

photosynthesis.

productivity—The amount of biological matter or biomass produced in a given 

area during a given unit of time.

propagate—To increase the number of organisms.

prop roots—Roots with their origin in stem or trunk tissue of a tree like red mangrove that supports the tree in soft, wet, and sometimes anaerobic substrates.

pseudo-bulb—Modified swollen base of a stem used for storing water as in some 

epiphytic orchids.

pubescence—Hairy covering of plant organs such as leaves and stems.

Pyrrophyta—a division of lower plants comprising unicellular and biflagellate 

algae that form starchy compounds.

raceme—Inflorescence having a common axis with stalked flowers attached.

rain shadow—Lack of rainfall on the leeward side of mountain ranges.

ramiflory—Flowers with their origin in woody branches.

reclamation—Rehabilitating a degraded or destroyed wetland or other habitat.

recovery plan—A plan for the restoration of protected or endangered species. 

May include captive breeding, disease control, and/or habitat management.

reef crest—Top of a reef on the ocean-facing side, which may experience air 

exposure.

reef front—The seaward side of a reef from the edge of the crest to the depth at 

which coral and coralline algae become rare.

reef slope—Area of increasing water depth on the seaward side of a reef.

reptile—Class of vertebrates including animals such as the snakes, lizards, turtles, 

and alligators.

reserve—An area that has a special use and is set aside for future use, including its 

natural resources.

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restoration ecology—Seeks to repair or reconstruct habitats and ecosystems 

damaged by human or natural actions.

rhizome—A thick horizontal stem usually in the soil, which sends out vertical 

shoots and descending roots at nodes.

riparian—Habitats having to do with riverbanks or corridors.

riverine—Feature or habitat related to rivers; wetlands that fringe rivers or are in 

channels.

root ball—Large clump of roots and soil exposed as a result of the uprooting of 

a tree.

rounded—Gently sloping apex of a leaf blade or tree top.

salamander—Small slender predatious amphibians.

saline (salinity)—Water containing salt in solution; sea water has a salinity of 

33 to 35 parts per thousand of NaCl.

SAV—Submerged aquatic vegetation, such as seagrass.

savanna—Subtropical or tropical grassland with drought-resistant vegetation and 

scattered trees; transitional between grasslands and rain forest.

saw timber—Trees that have sufficient length, girth, and proper development from 

which wood useful for construction or furniture can be sawn.

sclerophyllous (sclerophyllic)—Hard-leaved; leaves resistant to drought because 

of thick cuticle and reduced air space.

secondary species (forest)—The species or forest typical of an area that has been 

disturbed (natural or human induced) and is undergoing succession.

sediment (sedimentation, sedimentary)—The material such as released soil particles and organic matter that settles to the bottom of a liquid over long periods

(geologic). This can produce rock consisting of various-sized rock fragments

and remains of plants and animals, for example, limestone.

seed bank—When seeds are dispersed they may fall and not germinate and get 

incorporated into the soil in forest, field, and water bodies, only to germinate

later when conditions promote their germination.

sepal—Protective parts to a flower bud, usually green and located below the petals; 

collectively called the calyx.

serpentine (serpentinite)—A green-blue rock that gets its name from its mottled 

color similar to that of a serpent. A magnesium silicate, low in calcium that

produces changes in the usual plant cover of the area.

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General Technical Report IITF-35
sessile—Attached to the base of a leaf without a petiole or a flower without a 

peduncle.

shellfish—Any aquatic invertebrate animal having a shell, such as mollusks and 

crustaceans.

shrub—A woody plant with more than one main stem, usually less than 5 meters 

(15 feet) tall.

silviculture—The scientific process of producing and caring for a forest.

sink—An area benefiting from new recruitment of individuals from a distant 

source.

sinkhole—A depression or hollow place in which drainage collects and which may 

be open at the bottom leading to an underground channel or river. If solid,

some can be farmed.

slash-burn (swidden) agriculture—An ancient farming system in which small 

patches of tropical forest are cleared and perennial polyculture agriculture is

practiced, followed by many years of fallowing the land to restore the health of

the soil and the native vegetation.

soft coral—Coral that produces a soft, flexuous, exoskeleton that may take the 

form of feathers or fans, and show flexibility when water moves over them.

source—Opposite of a sink; an area that serves to export organisms such as immature forms of coral and fish to areas away from their origin.

sound—A long broad inlet of the ocean generally parallel to the coast.

speciation—The evolutionary development of new species.

species diversity—The number of different species and their relative abundance in 

a given area.

spelunker—A person who investigates caves.

spike—An elongated flower stalk with sessile flowers.

stilt roots—Long, slender, support roots with their origin in stem tissue; red mangrove, for example.

stipules—An appendage at the base of a leaf petiole where it attaches to a stem.

stomata—Openings in leaf and stem surfaces used in gas exchange.

stony coral—Limestone-secreting corals that are reef builders. Members exhibit 

polyps with six tentacles.

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stranglers—Woody plants that begin as epiphytes, later connect to the soil and 

produce a trunk that eventually kills the structural host tree. Ficus and Clusia,

for example.

stressor—An agent that can change the growth, reproduction, or physiological state 

of an organism or ecosystem, such as waste heat from a power plant or an oil

spill in a mangrove swamp.

sublittoral—Shallow water zone from the low tide point to about 200 meters 

(650 feet) deep.

submerged seagrass beds—Underwater populations of one or more species of 

flowering seagrasses, generally located in relatively clear water and soft to firm

substrates.

submergent—Wetland plant growing underwater attached to bottom substrates, 

such as water hydrilla (Hydrilla verticillata).

succession (successional)—Process in which communities of plant and animal 

species in a particular area are replaced over time by a series of different and

often more complex communities.

succulent—Plants that grow in warm areas and possess water storage capacity in 

fleshy stems, for example, cactus.

supralittoral—The seashore zone immediately above the normal tidal submergence 

zone.

sustainability—Ability of a system to survive for a specified period. 

swamp—Wetland type dominated by trees, such as mangrove swamps.

symbiosis (symbiotic)—The intimate living together of members of two different 

species.

Taínos—Caribbean Indians of the Greater Antilles with a complex social structure. 

They developed villages and practiced agriculture. Within 100 years of the

Spanish conquest, they became extinct.

tannin—Pigments found in the bark of woody plants used in tanning leather and 

dye pigments.

taxon—A generic term referring to a taxonomic unit of classification such as 

family, genus, or species.

termites—Social insects of the order Isoptera responsible for degrading vast 

quantities of plant biomass throughout the tropics; some species are very 

damaging to human-made wooden structures.

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General Technical Report IITF-35
termitophile—Interdependent organisms associated with termite colonies such 

as beetles, flies, protozoa, fungi, and bacteria.

terrace—A land or reef form that is nearly flat.

thallus—Body of a plant that lacks a true vascular system.

threatened species—A wild species that is still abundant in its natural range, but 

is declining and could become endangered.

topography—The physical features of the landscape.

trade winds—A tropical wind blowing almost continuously in the same direction, 

such as the easterly trades on the north side of the equator.

Tragedy of the Commons—The process of degradation of community resources 

owing to self-interest of individuals who use or destroy more than their fair

share, as in, overfishing.

tree—A woody plant with one main stem generally exceeding 5 meters (15 feet) 

in height.

tubercle—A small rounded protuberance on a plant or animal part.

turbid (turbidity)—A clouded or murky water condition owing to the presence of 

sediment, effluents, or biological agents that impede the penetration of light.

twice pinnately compound—Leaf condition where each leaflet is compound, 

that is, there is a double compound condition.

ultramaphic—Igneous rock rich in iron and magnesium and poor in silica.

upland—Elevated land away from the sea, a river or lake, or wetland.

urban desert—A result of the dense clustering of buildings, roads, and parking 

lots; many urban areas have little dedicated green space, thus they are often

desert-like.

urban forest interface—An area where an otherwise natural or wild undeveloped 

area is adjacent to an urbanized zone.

urbanization—The process of increasing human populations and support infrastructure in an urban area (city; generally considered 20,000 or more people).

vascular tissue—Xylem and/or phloem tissue in plants that permits movement of 

materials and adds strength.

vector—An agent that moves reproductive bodies such as pollen by bees and fruit 

or seeds by bats.

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vegetative—Growth in plants without reproduction; adds length, width, and 

biomass.

vertebrate—A subgroup of the chordata distinguished by the presence of a vertebral 

column, endoskeleton, and nerve cord.

vine—Slender woody plants that do not grow upright on their own, but use other 

plants or inanimate objects for support.

viviparous (vivipary)—Germinating while still attached to the parent plant, as 

seeds of red mangroves.

volcanic—Igneous rock composed of materials resulting from volcanism, such as 

lava.

water cycle—The natural solar-driven cycle of evapotranspiration, condensation, 

precipitation, and runoff.

well epiphyte—Water-collecting epiphytes frequently found attached to tree trunks 

in the wet tropics, such as the bromeliad Guzmania.

West Indies—Large island group of the Caribbean Sea region including the Greater 

and Lesser Antilles.

wetland—Ecosystems of several types in which rooted vegetation is found in 

specific soils that may be saturated with water much of the year such as bogs,

swamps, and marshes.

windbreak—Row of trees or shrubs planted to block windflow and reduce soil 

erosion on cultivated fields and sensitive habitats.

wind shear (training)—Process whereby the drying action of wind can reduce 

viability of buds on the windy side, causing greater growth on the protected

side.

winged—Having slightly expanded surface areas such as along a stem or leaf 

petiole.

xerophyte—Plant adapted to extremely dry conditions.

zonation—Arrangement of organisms and/or habitats based on biological, physical, 

and/or chemical features of the environment.

zooplankton—Microscopic animal plankton that float in water.

zooxanthellae—Small endosymbiotic dinoflagellate algae that live inside the inner 

gut cells of reef-building corals.

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Index

(Page numbers in bold signify Literature Cited)

adaptations: 85, 86, 89, 120, 163, 177, 178, 188, 200, 214, 266, 289, 314, 337, 394.

adventitious: 106, 115, 183, 197, 198, 199, 220, 404, 408.

aerenchyma: 200, 220, 223, 404.

African tulip tree: see Spathodea campanulata.

agroecosystems: 62, 70, 76, 105, 113, 135-137, 145, 329.

agroforestry: 135, 145, 153, 375, 404.

air plants: 117, 141.

algae: 117, 118, 129, 175, 189, 190, 191, 204, 216, 219-229 passim, 232, 235, 236, 

237, 242, 244, 246, 248, 251, 259- 270 passim, 280, 281, 324, 334, 347, 

378, 380, 404-419 passim, 424.

Pyrodinium bahamense: 347, 378.

Halimeda: 189, 205, 230, 244, 251, 261, 347, 352, 407.

macrobenthic algae: 219, 224, 226, 227, 229, 242, 251, 270, 378.

alien species: 1, 27, 33-34, 36, 45, 48, 51, 52, 55, 56, 71, 84, 232, 346, 305, 366

alluvial: 2, 25, 26, 80, 88, 91, 104, 304, 331, 404.

Amazona vittata: 42, 55, 56 passim, 60, 72, 125, 355.

amphibian(s): 44, 47, 50, 52, 54, 67, 71, 72, 287, 292, 318, 337, 338, 353, 354,

402, 404, 420

Bufo marinus: 48, 353.

Eleutherodactylus coqui (coquí): 44, 50, 52-54, 72, 337, 342, 353.

frogs: 47, 48, 52, 54, 71, 102, 118, 130, 339, 371-372, 404, 407.

Puerto Rican crested toad (Peltophryne lemu): 47, 48, 72, 89, 354, 390.

toads: 47, 48, 404.

tree frogs: 48, 52-55, 118, 130, 337, 371-372.

Anacardiaceae: 32, 37, 154, 155, 336, 377.

anthozoa: 233, 244, 254, 407.

anthropogenic: 177, 232, 245, 270, 284, 314, 315, 405, 412.

aquatic beds: 168, 169.

Arecibo Ionospheric Observatory: 98, 370, 374.

atolls: 239, 242.

Australian pine: see Casuarina equisetifolia.

autograph tree: see Clusia rosea.

Avicennia germinans: see mangroves, black.

avocado: 27, 64, 345.

Bacardi rum distillery: 66, 372.

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Guide To The Ecological Systems Of Puerto Rico
bagasse: 140, 405.

Banana Republics: 148

bananas: 2, 32, 62, 64, 79, 134, 136, 137, 148-151, 313, 314, 337, 345.

bank reef: 242, 405.

barrier reefs: 239, 242, 405.

Great Barrier Reef: 247, 268, 395.

bats: 43, 45, 47, 48, 50, 63-67, 112, 184, 292, 306, 318, 319, 326, 327, 329, 330,

334, 338, 339, 340, 370, 372, 392, 394, 413, 423.

benthic: 204, 216, 221-232 passim, 271, 333, 378, 405, 414.

bicameral: 12, 405. 

biodiversity hotspot: 314, 317, 318.

bioluminescence: 329, 338, 377, 378, 405.

bioluminescent bay: 378.

bleaching: 246, 249, 267, 268, 269, 270, 271, 312, 313, 314, 317, 319, 321, 323,

328, 405, 407.

bloodwood: 104, 161-163 passim, 167, 214, 342, 352.

bog: 127, 157, 165, 172, 173, 405, 424.

Boqueron Bay: 170, 248, 369.

Borínquen: 4, 5.

botanical garden: 33, 125, 156, 287, 369, 370, 371, 400.

breaker zone: 242.

bromeliad (Bromeliaceae): 54, 107, 115-121 passim, 129, 134, 141, 335, 350, 

351, 424.

Vriesea sintenisii (red leaf bromeliad): 121, 134, 351.

Bursera simaruba: 33, 88, 91-92, 180, 193, 348.

buttress: 29, 39-41, 77, 104, 105, 109, 162, 163, 242, 406.

Caribs: 4, 5, 406.

castes: 68.

Cabo Rojo: 20, 57, 75, 86, 138, 143, 238, 301, 302, 306.

Cabo Rojo National Wildlife Refuge: 57, 75, 211, 304, 340, 382, 401.

Caguana Indian Ceremonial Park: 368.

Caribbean Islands National Wildlife Refuge (CINWR): 304, 340, 390, 401.

Caribbean National Forest (CNF): 88, 95, 115, 116, 119, 162, 291, 339, 373, 375, 

393, 398, 400.

carton: 69, 70, 406.

Casuarina equisetifolia: 168, 180, 185-186, 335, 345.

catadromous: 52, 157, 406.

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General Technical Report IITF-35
cauliflory: 32, 105, 406.

caves at Camuy: 369, 372.

Cecropia schreberiana: 33, 107, 111-112, 134, 323, 352.

Ceiba pentandra: 32, 39-40, 324, 348, 411.

chitons: 44, 188, 190, 191.

chlorosis: 180, 186, 279, 406.

CITES agreement: 367.

citrus: 2, 62, 134, 136, 137, 148, 151-154, 346, 347, 348, 349.

citrus sinensis: 152, 349.

cleaning symbiosis: 264, 266, 331, 332, 336, 406.

Clusia rosea: 32, 43, 105, 119, 129, 134, 168, 326, 345.

cnidaria: 44, 233, 235, 237, 407, 415, 416.

cnidocytes: 235.

cobana negra: 73, 75, 346.

Coccoloba uvifera: 32, 177, 180, 184-185, 192, 336, 351.

coconut palm: see Cocos nucifera.

Cocos nucifera: 32, 168, 180, 181-183, 346.

coelenterata: 233.

coelenteron: 235, 407.

Coffea arabica: 1, 2, 7, 8, 9, 19, 32, 58, 59, 62-63, 76, 79, 104, 112, 113, 135-138

passim, 143-148, 346. 

shade-grown coffee: 62, 113, 146.

sun-grown coffee: 59, 62, 63, 146.

Coffee: see Coffea arabica

colonial period: 7-8, 138.

commonwealth: 3, 11-19 passim, 57, 59, 74.

Comocladia glabra: 38, 102.

dodonaea: 37, 38, 88, 102.

conquistadores: 6, 7, 43.

coppicing: 84.

corals: 44.

Acropora cervicornis: 231, 250, 256-257, 269, 280, 281, 356.

Acropora palmate: 190, 191, 250, 255-256, 269, 280, 281, 356.

Diploria labyrinthiformis: (brain coral) 251, 257-258, 269, 356.

-strigosa: (depressed brain coral) 251, 258, 356.

bleaching: 246, 267-271 passim, 312, 313, 314, 317, 319, 321, 323, 328, 405.

finger coral: 231, 250, 254, 280, 356.

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Guide To The Ecological Systems Of Puerto Rico
grooved brain coral: 257.

hermatypic coral: 236, 412.

horned coral: 255, 356.

Porites spp.: 231, 254-255, 280, 281, 356.

Porites astreoides: 255, 356.

Porites furcata: 356.

Porites porites: 250, 254, 356. 

coral reefs: 1, 2, 23, 50, 52, 86, 95.

shallow-water stony corals: 242, 244, 250-251, 311, 322.

soft coral: 244, 251, 259, 264, 269, 280, 407, 421.

staghorn corals: 231, 242, 250, 256, 257, 269, 280, 281, 356.

stony corals: 244, 250, 254, 311, 322.

thick finger coral: 254, 356.

thin finger coral: 254, 356.

Cordillera Central: 8, 19, 20-25 passim, 31-33, 86, 95, 98, 106, 109, 115, 123, 147.

cupey: 43-44.

Cyathea arborea: 106-107, 134.

Cyrilla racemiflora: 31, 125, 127-128, 134.

Dacryodes excelsa: 109-110.

de Leon, Ponce: 6.

Delonix regia: 32, 36, 41-42.

detritus: 188, 203, 216, 221, 237, 408.

Diadema antillarum: 191, 230, 251, 261, 262, 361.

dinoflagellates: 264, 347, 378, 408, 424.

diurnal: 49, 182, 215, 408.

drip-tip leaves: 105.

drought: 119, 130, 209, 213, 216, 267, 282, 284, 285, 408, 420.

dunes: 175-180 passim, 184, 186, 187, 304, 324, 335.

ecological life zones: 79, 82.

ecological services: 171, 172, 244, 313, 408.

ecosystem management: 297, 409.

ecotourism: 3, 4, 57, 65, 213, 245, 248, 249, 294, 326, 329, 363, 383, 397, 409.

ecotone: 131, 409, 411.

effluent: 170, 189, 232, 246, 249, 409, 423.

El Morro: 7, 369.

El Niño: 232, 268, 271, 313, 317, 409.

El Portal: 119, 294, 295, 375, 398, 400.

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El Yunque: 20, 55, 57, 65, 106, 108, 116, 119-121 passim, 124, 133-135 

passim, 275, 276, 291-299 passim, 384, 398-400 passim.

emergent vegetation: 167, 307.

endemism: 30, 34-36 passim, 313.

endosymbiotic: 235, 237, 268, 405, 407, 409, 424. 

Epicrates inornatus: 48, 72, 74, 359, 392.

epifauna: 207, 221, 410.

epiphyllous: 118.

epiphyte: 32, 43, 62, 95, 101, 105, 106, 108, 114-122, 124, 125, 129, 133, 134, 

141, 163, 200, 225, 289, 322, 329, 333, 337, 352, 372, 410, 422, 424.

bracket epiphyte: 119.

hemiepiphyte: 119

protoepiphyte: 119.

tank epiphytes: 117, 119, 352, 372.

well epiphyte: 117, 424.

epixylous: 118.

estuarine: 157, 165, 168-170 passim, 195, 216, 306, 323, 410.

eutrophication: 161, 213, 246, 268, 410.

Fabaceae: 30-32 passim, 35, 410, 414.

facultative: 167, 168, 201, 410.

upland: 168.

wetland: 116, 167.

fauna: 27, 36, 42, 45, 46, 50, 52, 74, 102, 205-207 passim, 216, 221, 223, 226, 244,

261, 317, 320, 325, 335, 410.

field trip (checklist): Preface, 213, 249, 287, 310, 363, 365, 368, 370-373 

passim, 377, 380, 381. 

fire: 59, 65, 84, 85, 107, 139, 282, 285, 286, 291, 308, 418.

flamboyan tree: see Delonix regia.

floating attached vegetation: 166.

flora: 27, 30, 31, 33, 34, 35, 102, 120, 121, 123, 124, 125, 127, 132, 134, 172, 206,

223, 285, 313, 315, 317, 322, 329, 331, 336, 341, 370, 410.

Fomento: 11.

Foraker Act: 9-10.

forereef: 242, 411.

deep: 242.

forest(s)

cloud forest: 121, 128, 131, 133, 157, 321, 342, 383, 407.

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Guide To The Ecological Systems Of Puerto Rico
colorado forest: 115, 125, 127, 128, 133.

Commonwealth: 57, 82, 107.

dry: 23, 26, 36, 58, 80, 83, 84, 85, 86, 118, 334.

Guánica Forest: 21, 59, 86, 88, 89, 92, 93, 118, 123, 130, 183, 192, 202, 304, 

315, 326, 369, 372, 373, 400.

moist forest: 26, 38, 44, 82, 94, 95, 102, 104, 108, 220.

rain forest: 20, 21, 26, 59, 65, 80-88 passim, 105, 108, 111-122 passim, 131, 

157, 203, 233, 278, 285, 291, 294, 315, 317, 318, 319, 320, 322, 324, 326,

334, 335, 337, 338, 373-375 passim, 385, 393, 394, 420.

subtropical moist forest: 82, 94-105, 108, 220.

fragmentation: 58, 411.

frangipani: see Plumeria rubra, 180, 193, 347.

free-floating vegetation: 166.

fronds: 106, 114, 116, 119, 131, 181, 182.

frugivore: 65, 411.

genetic bottleneck: 269, 411.

global climate change: 175, 232, 270, 277, 342, 412.

Gorgonians: 244, 258, 259, 281, 321.

Gorgonia flabellum: 251, 259, 267, 360.

sea fans: 233, 244, 259, 267, 360.

Greater Antilles: 5, 16, 18, 27, 30, 35, 46, 47, 76, 123, 162, 174, 412, 422.

greenspace: 285, 287, 289, 290.

gross domestic product: 17, 411.

Guánica: 8, 20, 21, 23, 26, 36, 37, 50, 57, 59, 75, 84, 85, 86, 88, 89, 90, 169, 183, 

184, 192, 304, 315, 326, 369, 372, 373, 384, 400.

Gumbo limbo: see Bursera simaruba

Guzmania berteroniana: 115, 120, 121, 134, 352.

Hacienda Buena Vista: 298, 375.

Halodule wrightii: 169, 223, 225, 226, 252, 351.

beaudettei: 221, 252.

halophytes: 195.

haystack hills: 23, 37, 44, 98, 100, 101, 102, 370, 373, 374, 413, 418.

Holdridge life zone system: 81.

hurricane(s): Preface, 1, 20, 21, 23, 44, 46, 80, 111, 116, 120, 128, 131, 137, 150, 

162, 170, 187, 201, 225, 232, 246, 249, 257, 273-282, 312, 313, 316, 318,

320, 333, 338, 341, 342.

effects: 23, 273, 276, 278, 279, 280, 281, 297.

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General Technical Report IITF-35
disturbance systems: 277.

Hurricane Hugo: 110, 130, 274, 275, 276, 278, 321, 322, 327, 341, 342.

indigenous ceremonial parks: 368.

Inceptisols: 25.

insects: 44, 46, 48, 49, 53, 54, 63, 64, 65, 66, 67, 118, 183, 190, 317, 320, 340,

342, 377, 413, 422.

termites (Nasutitermes costalis): 44, 48, 67-70, 91, 204, 263, 317, 330, 361, 

406, 422.

interference competition: 224, 413.

International Institute of Tropical Forestry: 59, 80, 107, 287, 291, 296, 310.

invertebrates: 54, 67, 204, 219, 226, 230, 235, 251, 255, 272, 277, 292, 328, 377.

Jamaican walnut: 31, 76-77.

Jardin Botánico: 370.

Jones Act: 10-11.

Juglans jamaicensis: 73, 76-77, 326, 348, 353.

kapok: see Ceiba pentandra.

karst: 20, 23, 37, 38, 44, 48, 66, 71, 80, 95-102, 120, 124, 143, 188, 298, 301, 304, 

316, 327, 334, 369, 370, 372, 373, 374, 392, 401, 412, 413.

La Parguera: 69, 120, 209, 222, 248, 249, 250, 253, 255, 258, 260, 263, 301, 321,

322, 325, 327, 363, 377-382 passim.

lacunae: 220, 223, 413.

lacustrine: 165, 413.

lagoon: 49, 165, 169, 195, 207, 213, 214, 219, 223, 225, 239, 242, 244, 250, 254, 

255, 256, 257, 258, 259, 281, 301, 302, 306, 307, 376, 377, 379, 382, 405,

411, 414.

Laguna Cartagena Refuge: 382.

Laguncularia racemosa: 167, 169, 195, 201, 353.

Lake Tortuguero: 49, 173.

landslides: Preface, 25, 106, 111, 131, 276, 277, 282, 284, 331, 334.

Las Cabezas Nature Reserve: 373.

leaves: 28, 29, 37-41 passim, 43, 53, 54, 66, 75, 77, 84-86 passim, 91-93 passim, 

101, 102, 105, 106, 109-121 passim, 125, 127-131 passim, 139, 141, 144,

145, 149, 152-156 passim, 156, 162, 167, 177, 178, 181, 182, 184, 186,

196-203 passim, 206, 210, 216, 220-225 passim, 285, 372, 379, 404, 408,

411-420 passim.

Lesser Antilles: 5, 19, 27, 35, 46, 162, 263, 273, 329, 388, 406, 414, 424.

lianas: 62, 289.

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Guide To The Ecological Systems Of Puerto Rico
life zones: 79, 80, 82-84 passim, 104, 108, 112, 113, 114, 125, 131, 132, 196, 313.

limestone: 23-26 passim, 75, 94, 95, 98, 103, 170, 184, 189, 193, 202, 235, 244, 

268, 301, 370, 373, 376, 401, 413, 414, 420, 421.

limestone hills: 3, 95, 99, 373, 376.

littoral zone: 199, 261.

long-spined black sea urchins: 191.

lower montane forests: 80.

wet: 125, 128, 131-132.

rain: 82, 132-133.

lower montane life zones: 125.

Luquillo Experimental Forest, Luquillo rain forest, Luquillo Mountains: 20-21, 

35-36, 88, 95, 102, 106-110 passim, 114-116 passim, 128-135 passim, 157, 

171, 284, 285, 291-294 passim, 297-299 passim, 312, 315, 319, 320, 321,

323, 327, 332, 338, 340, 341, 342.

macroepiphytes: 118, 130.

mammals: 44, 45, 47, 51, 63, 64, 67, 71, 72.

manatee grass: 169, 221, 224, 252, 349.

mangoes: 1, 64, 154-156, 366.

mangroves: 1, 31, 32, 104-105, 169, 170, 201, 203-205 passim, 208-214 passim, 

228, 246, 301-302 passim, 312, 316, 317, 318, 319, 322, 324, 329, 332, 333,

335, 336, 337, 339, 378, 384, 394, 410, 411.

black mangrove (Avicennia germinans): 31, 32, 167, 169, 195, 198-200, 201, 

207, 330, 345, 379, 418.

red mangrove (Rhizophora mangle): 32, 69, 128, 167, 169, 195, 196-200, 

203-207, passim, 210, 219, 328, 330, 351, 373, 378, 379, 381, 387, 

411, 424.

white mangrove (Laguncularia racemosa): 167, 169, 195, 201, 353, 410.

buttonwood mangrove: 180, 189, 192, 195, 346.

mangrove swamp: 1, 51, 57, 157, 169, 197, 200, 204, 207, 210, 211, 213, 227, 239, 

245, 249, 261, 263, 278, 281, 298, 300, 301, 306, 319, 364, 379, 399, 422.

Maricao: 23, 52, 55, 108, 113, 123, 136, 300, 353, 369. 

mariculture: 266, 414.

marine: 1-4 passim, 15, 17, 34, 42, 45, 47, 48, 51, 72, 74, 86, 157, 166, 169, 170, 

181, 203, 211, 213-215 passim, 219, 222, 223, 227, 229, 232-300 passim,

311, 312, 313, 314, 318, 322, 325, 328, 331, 335, 337, 341, 353, 363, 377,

380, 399, 404-415 passim.

marine reserves: 260, 316, 318.

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General Technical Report IITF-35
marl: 23, 376, 377.

marshes: 157, 165, 168-171 passim, 197, 211, 424.

microepiphytes: 118, 130, 154.

microphylly: 85.

migration: 14, 34, 44, 52, 56, 58, 60, 63, 151, 177, 214-216 passim, 284, 287, 

317, 323.

mitigation: 171, 172, 307, 415.

mogotes: 28, 98, 100.

Mollisols: 25.

mongoose: 47, 51, 53, 57, 306, 358.

Herpestes auropunctatus: 358.

monoculture: 9, 58, 62, 131, 136-138 passim, 145, 162, 196, 198, 404, 415.

mountain oak: 130, 134.

Musa paradisiaca: see bananas.

mutualism: 264-265 passim, 315, 416.

Myrtaceae: 30, 31, 35. 

nematocyst: 407, 416.

Neotropical migrants: 57-63, 145, 372.

niche: 49, 53, 55, 266, 277, 416.

obligate upland: 168.

obligate wetland: 167.

oligotrophic: 249, 416.

Operation Bootstrap: 11, 411.

orchids: 30, 31, 63,71, 73, 74, 102, 107, 114, 117-119 passim, 121-125, 134, 172, 

311, 371, 377, 419.

Organic Act: 9-10.

orographic rain shadow: 19, 20, 27, 86, 417.

palo Colorado: see Cyrilla racemiflora, 73, 115, 125, 127, 128, 131-133 passim, 

167-168, 295, 349.

palustrine: 161, 165, 168, 172, 302, 307, 417.

palm brake: 115, 116, 128, 131-133 passim.

parrot(s): 57, 171, 276, 292, 293, 297, 339, 355, 393.

parthenocarpic: 150, 417.

Partners in Flight: 59, 392.

Peltophryne lemur: 47, 48, 89, 354.

petroglyphs: 368, 417.

phase shift: 261, 263, 271, 280, 329, 417.

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Guide To The Ecological Systems Of Puerto Rico
phosphorescent bay: 209, 258, 301, 308, 377-379 passim, 382, 385.

phytoplankton: 177, 237, 338, 418.

pineapple: 32, 79, 104, 137, 141-143, 350, 366, 415.

Plumeria rubra: 32, 88, 92-93.

pneumatophores: 32, 163, 198-199, 200-201 passim, 410, 418.

Poaceae: 31, 32, 137, 221.

poison plants: 155, 289.

pollinators: 64, 118, 120-123 passim, 277, 413, 418.

Polypodiaceae: 30-31 passim.

polyps: 188, 235, 237, 242, 254, 257, 259, 264, 405, 416, 421.

postcard tree: see Clusia rosea, 345.

Prestoea montana: 114, 115-116, 128, 131, 134, 167, 168, 327, 332, 351.

prop roots: 32, 43, 115, 131, 195-210 passim, 419.

Psilotum nudum: 31, 163, 353.

Pterocarpus officinalis Jacq.: See bloodwood and 104.

Puerto Rican boa: see Epicratus inornatus, 292, 359.

Puerto Rican Conservation Trust: 298, 303.

Puerto Rican parrot: see Amazona vittata.

rain shadow: 1, 19, 25, 86.

rear zone: 242, 255.

reclamation: 172, 173, 186, 211, 302, 419.

recovery plans: 71, 390.

reef(s): 242, 419.

reef crest: 242, 419.

reef flat: 242.

fringing reefs: 51, 239, 242, 248, 255, 256, 411.

reef front: 419.

patch reef: 242, 255, 417.

reptiles: 44-51 passim, 54, 67, 71, 72, 230, 287, 318, 336, 337, 338, 359-360, 

371, 402.

Caiman crocodiles: 50, 53, 359, 360, 377.

Caretta caretta: 50, 72, 312, 359.

Chelonia mydas: 45, 50, 72, 227, 230, 312, 359.

green sea turtle: 50, 72, 222, 227, 230, 359.

loggerhead turtle: 312.

sea turtles: 45, 50 72, 172, 221, 222, 232, 306, 382, 388-391 passim, 394.

spectacled caiman: 50, 359, 360.

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General Technical Report IITF-35
rhizomes: 148, 177, 179.

riparian: 58, 181, 290, 420.

riverine estuary: 213, 217.

roble de sierra: 129, 130, 351.

rocky shorelines: 184, 188.

saline: 88, 198, 219, 306, 412, 420.

salt flats: 169, 171, 300, 306.

sandy beach: 3, 27, 174-188 passim, 248, 249, 300, 377, 379.

scleractinia: 233, 254, 341.

sea grape: see Coccoloba uvifera.

seagrass (beds): 1, 50, 51, 157, 169, 170, 177, 203, 213, 219-232 passim, 237, 242, 

245, 249, 254, 255, 261, 263, 278, 281, 313, 314, 322, 325, 327, 328, 329,

330, 334, 335, 336, 339, 341, 349, 351, 373, 377-381 passim, 387, 414, 420,

422.

sedimentation: 21, 223, 232, 246, 256, 280, 420.

seed bank: 297, 420.

serpentine: 31, 94, 102, 108, 312, 323, 351, 369, 420.

shoal grass: 169, 221, 223-226, 252, 351.

sierra palm: see Prestoea montana, 114, 115, 116, 128, 131-134 passim, 167, 168, 

196, 295, 301, 332, 351.

sink: 263, 421.

sinkholes: 23, 44, 98, 102, 300, 370, 374, 384, 403, 413, 418, 421.

slope zone: 242.

soils: Preface, 19, 20, 25, 26, 44, 76, 84, 88, 93, 94, 101-109 passim, 116, 129-132 

passim, 136, 138, 143, 145, 152, 157, 162, 166-169 passim, 182, 183, 193,

196-199 passim, 207, 210, 211, 267, 282, 284, 292, 293, 298, 300, 308, 320,

323, 324, 333, 352, 377, 408-410 passim, 412, 414, 420-424 passim.

solution cave: 370, 374.

source: 7, 11, 17, 19, 23, 30, 34, 35, 68, 69, 72, 83, 85, 89, 113, 118, 135, 144, 147, 

151, 154, 186, 197.

Spathodea campanulata: 1, 27, 28-29, 33, 36, 134, 326, 345.

species:

charismatic: 42, 406.

endangered: 2, 35, 41, 45, 50, 70-71, 74, 75, 76, 101, 124, 161, 172, 269, 306, 

367, 382, 387, 390, 391, 392, 406, 409, 419.

keystone: 413.

naturalized species: 34, 36, 123, 183, 416.

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Guide To The Ecological Systems Of Puerto Rico
threatened species: 245, 423.

Stahlia monosperma: 73, 75, 305, 346.

stranglers: 105, 119, 120, 422.

stressors: 58, 62, 192, 206, 209-211, 232, 267.

submerged aquatic vascular vegetation: 219. 

submergent vegetation: 166, 376.

succulents: 85.

sugarcane: 1, 7, 20, 25, 32, 48, 79, 104, 113, 137-141, 143, 144, 149, 162, 170, 

307, 352.

supralittoral: 177-179 passim, 190, 422.

sustainability: 3, 309, 422.

swamp bloodwood: see Pterocarpus officinalis Jacq., 161, 162-163, 167, 168, 

214, 352.

swamps: 1, 3, 51, 57, 125, 157, 162, 165-169 passim, 197, 211, 213, 214, 227, 239, 

245, 249, 261, 263, 278, 281, 300-302 passim, 304, 306, 319, 364, 379, 395,

422, 424.

sweet orange: 151, 153, 154.

Swietenia mahagoni: 36, 93, 353.

symbiosis: 123, 213, 235, 263, 264, 266, 315, 331, 332, 334, 336, 406, 422.

Syringodium filiforme: 169, 221, 224, 225, 252, 349.

Tabebuia rigida: 129, 130, 134, 351.

tabonuco: see Dacryodes excelsa, 65, 107, 108, 115, 125, 132, 134, 295, 327,

332, 352.

termitophiles: 67, 68, 423.

Thalassia testudinum: 166-169 passim, 221-225 passim, 252, 325, 353, 

378-380 passim.

tide pools: 190-192.

Tillandsia recurvata: 120, 345.

Trade Winds: 1, 19, 20, 46, 86, 267, 273, 291, 423.

tree ferns: see Cyathea arborea, 106, 133, 347, 351, 352.

trumpet tree: see Cecropia schreberiana.

turbidity: 219, 223, 236, 249, 268, 278, 279, 423.

turtle grass: See Thalassia testudinum.

Ultisols: 25.

urban forest interface: 285, 287, 289, 423.

urbanization: 3, 19, 25, 33, 79, 172, 209, 282, 287, 423, 

vector: 27, 43, 64, 77, 112 155, 183, 199, 277, 365, 366, 408, 413, 423.

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