Susan M. Stein, Mary A. Carr, Greg C. Liknes, and Sara J. Comas

Islands on the Edge:

Housing Development 

and Other Threats to 

America’s Pacific and 

Caribbean Island Forests

A Forests on the Edge Report

United States Department of Agriculture

Forest

Service

General Technical

Report NRS-137

Northern

Research Station August 2014

State and Private

Forestry
ABSTRACT

Stein, Susan M.; Carr, Mary A.; Liknes, Greg C.; 

Comas, Sara J. 2014. Islands on the edge: housing 

development and other threats to America’s Pacific 

and Caribbean Island forests: a Forests on the Edge 

report. Gen. Tech. Rep. NRS-137. Newtown Square, 

PA: U.S. Department of Agriculture, Forest Service, 

Northern Research Station. 55 p.

This report provides an overview of expected housing 

density changes and related impacts to private forests 

on America’s islands in the Pacific and Caribbean, 

specifically Hawaii, Guam, American Samoa, the 

Commonwealth of the Northern Mariana Islands, 

Puerto Rico, and the U.S. Virgin Islands. We discuss the 

vulnerability of island forests to conversion for housing 

development, introduction and spread of invasive 

species, and risk of uncharacteristic wildfire, among 

other concerns. Our maps and projections suggest that 

in localized areas from 3 to 25 percent of private forest 

land is likely to experience a substantial increase in 

housing density from 2000 to 2030. Resource managers, 

developers, community leaders, and landowners 

should consider the impacts of housing development 

and invasive species on ecosystem services in coming 

decades. 

Key Words: housing density, tropical forests, 

 subtropical forests, ecosystem services

Authors

Susan M. Stein is the director of U.S. Department of 

Agriculture’s National Agroforestry Center, and was 

formerly coordinator of private forest land studies for 

the U.S. Forest Service. She can be contacted at 

sstein@fs.fed.us. Mary A. Carr is a technical 

publications editor, U.S. Forest Service, Publishing Arts, 

Olympia, WA. Greg C. Liknes is a research physical 

scientist, U.S. Forest Service, Northern Research Station, 

St. Paul, MN. Sara J. Comas is a natural resource 

specialist, U.S. Forest Service, Cooperative Forestry 

Staff, Washington, D.C.

Introduction

T

he Pacific and Caribbean islands that are U.S. States, 

territories, or otherwise affiliated with the United 

States include virtually all the Nation’s tropical 

forests as well as other forest types including subtropical, 

coastal, subalpine, dry limestone, and coastal mangrove 

forests. Although distant from America’s geographic 

center and from each other—and with distinctive 

flora and fauna, land use history, and individual forest 

issues—these rich and diverse ecosystems share a 

common bond of change and challenge. 

Island forests are subject to pressures that are similar to 

those on the mainland, including conversion of forest 

for housing, agriculture, and industry; introduction and 

spread of invasive species; and risk of uncharacteristic 

wildfire. But islands by their nature, with relatively small 

or constrained land areas and fresh water limitations, can 

be more vulnerable than mainland areas to such impacts. 

This report provides an overview of expected housing 

density changes and related impacts on America’s 

Pacific and Caribbean island forests. These areas 

are often overlooked in forest assessments owing to 

insufficient or incompatible data. Specifically we discuss 

forests located on: 

• Pacific Islands1

: Hawaii, Guam, American Samoa, 

and the Commonwealth of the Northern Mariana 

Islands 

• Caribbean Islands: Puerto Rico and the U.S. Virgin 

Islands

1

We do not include discussion of other Pacific islands 

affiliated with the United States, such as the Republic of 

the Marshall Islands, Federated States of Micronesia, and 

Republic of Palau, because sufficient data are not available to 

provide housing density projections for these areas.

Hanalei Valley, Hawaii. Photo by Skibreck, istockphoto.com.

Photo by J.B. Friday.


About Forests on the Edge 

Forests on the Edge (FOTE) is a project developed 

by the U.S. Forest Service in conjunction with 

universities and other partners. The project aims to 

increase public understanding of the contributions 

of and pressures on America’s forests and to create 

new tools for strategic planning. This report is one 

of several FOTE reports that identify areas across 

the Nation where private forests might change 

because of housing development and other factors. 

Although previous reports have focused on the 

conterminous 48 United States, this report focuses 

solely on Pacific and Caribbean island forests. 

For each area, we present an overview of forest 

geography and human population trends; selected forest 

issues and priorities as identified in recent assessments; 

and maps and projections of housing density in coming 

decades. Case studies highlight specific places and 

situations that illustrate the trends or issues relevant for 

the area under consideration.

Table 1. America’s subtropical and tropical islandsa

Total land Existing forestb Percent of forest Population

Islands areab (acres) (acres) (percent) privately ownedc (2010)d

 Pacific

 Hawaii 4,125,125 1,676,516 41 46 1,360,301

 Guam 133,966 63,663 48 69 159,358

 American Samoa 47,123 23,868 51 85 55,519

 Commonwealth of the 

 Northern Mariana Islands 75,139 49,948 67 78 53,883

 Caribbean

 Puerto Rico 2,187,577 1,020,400 47 87 3,725,789

 U.S. Virgin Islands 84,226 53,278 63 83 108,612

a Republic of the Marshall Islands, Federated States of Micronesia, and Republic of Palau are not included in this report due to insufficient data. b NOTE: Acreages and percentages of total land area and forest cover presented in this table reflect data analyzed for this project. They may differ 

from statewide resource assessments, FIA data and reports, or other sources because of differing ways of classifying and calculating forest land 

area. Because forest land definitions vary by location, local expertise was consulted to determine which land cover or vegetation categories in the 

data layers should be considered forest. See appendix for details. Land cover can change rapidly; the data used for this report represent snapshots 

in time for the purposes of modeling and analysis.

c Percentages of private forest reflect a combination of data for land cover as described in the Methods section and ownership data from Theobald 

(2005). 

d U.S. Census Bureau (2011a-e). Population data for 2010 are provided here and in the text to provide a glimpse of recent population numbers. 

However, the analysis for this report was based on Theobald (2005), which used data from the 2000 census; updated housing density data for the 

trust territories were not available at the time of this analysis.

Private Forest Values: Benefits

and Challenges on the Islands

I

n the contiguous 48 States, more than half the forests 

are privately owned (Smith et al. 2009); in the Pacific 

and Caribbean islands described in this report, the 

proportion of privately owned forest varies but is as 

great as 87 percent (Table 1). Regardless of their extent, 

private forests play a key role in protecting water 

quality, furnishing diverse habitats for fish and wildlife, 

providing the raw materials for timber products and 

other forest goods, and sustaining valuable ecological 

functions such as flood and climate regulation across the 

landscape2 (Smail and Lewis 2009). 

Private forests on the islands are particularly important 

to biological diversity and the supply of water, wood, 

recreation, and social values for people (West. For. 

Leadership Coalition 2010). These islands support 

highly diverse native ecosystems with unique and 

often endangered plant and animal species, significant 

coral reef systems, and human populations that are 

substantially dependent on traditional subsistence 

lifestyles (Cannarella 2010, Carpenter et al. 2007, 

U.S. Forest Service 2007).

2

 Such goods and services are often referred to as “ecosystem 

services;” for more information, visit the Forest Service 

ecosystem services Web site: 

http://www.fs.fed.us/ecosystemservices.
What Are Private Forests?

Private forests are forest lands owned by 

individuals, families, corporations, organizations, 

tribes, or the forest industry. Public forest lands 

are those owned by Federal, State, or local 

governments. Public forests are not available 

for residential development but can be affected 

by increased housing density on or near their 

boundaries (Stein et al. 2009). 

Forests in Hawaii are critical for supplying clean water. Photo by twildlife, istockphoto.com.

The exceptional benefits provided by tropical and 

subtropical island forests include (U.S. Forest Service 

2007):

• Rich array of flora and fauna often found nowhere 

else in the Nation or the world 

• Diverse human cultures knowledgeable about 

sustainable agroforestry systems and cultural uses 

of forest products that could help guide future 

management of continental areas

• Forest ecosystem services such as fresh water 

aquifers and river systems, reef protection, and 

shoreline shelter and protection 

• “Early warning” indicators for global warming, 

sea-level change, storm frequency and severity, 

environmental degradation, and effects of climate 

and environmental change

• Unique opportunities for scientific research in the 

ecology and sustainable management of tropical and 

subtropical forests

Although each island is different, the forest products 

and ecosystem services they support are at risk when 

forest land is altered or lost. Some islands experience 

temporary or permanent population booms resulting 

in direct conversion of private forests to housing and 

other developments. Many islands serve as conduits for 

the movement of people and invasive species back and 

forth between mainland and island, contributing to the 

spread of nonnative plants and animals that can disrupt 
Urban Forests 

on the Islands

Urban forests are particularly important 

on tropical islands, where they provide 

essential green infrastructure for 

diverse lowland and coastal plant and 

animal communities. These forests 

are the first line of defense from 

catastrophic storms and inland water 

runoff. These forests also reduce city 

temperatures by providing shade, 

provide refuge for migrating birds, 

reduce air pollutants, contribute to 

carbon sequestration, and supply a 

host of other ecological and social 

benefits (Cannarella 2010). Footbridge in a mangrove forest, Aguirre State Forest, Guayama, Puerto 

Rico. Photo by Magaly Figueroa, U.S. Forest Service, International 

Institute of Tropical Forestry.

Housing Density

As in previous Forests on the Edge studies, the terms 

housing development and increased housing density 

refer to an increase in the number of housing units3 per 

unit area on rural lands such that the housing density 

shifts from either the rural I or rural II categories to 

a higher density category (Stein et al. 2007, 2009; 

Theobald 2005), where: 

• Rural I is 16 or fewer housing units per square mile; 

• Rural II is 17 to 64 housing units per square mile4

; 

and 

• Exurban-urban is 65 or more housing units per 

square mile. 

Housing density projections were prepared by David 

Theobald, using the approach described in Theobald 

(2005). The projections are based on several factors, 

including past and current statistics on housing density 

and population5, past growth patterns, road densities, 

ecological cycles and displace native species. All the 

islands considered here are vulnerable to the effects of 

climate change, especially with regard to sea level rise, 

hurricanes, and droughts. 

Like their mainland counterparts, private forest 

owners on America’s Pacific and Caribbean islands 

are frequently under economic and societal pressure 

to sell their land for development or other uses (Alig 

2007). However, market-based approaches that provide 

landowners with economic incentives to retain and 

conserve forest lands may not be widely available, 

understood, or accepted. Finding the right balance 

among often divergent values for private forests can be 

an enormous challenge for island forest landowners and 

managers.

Methods: How We Studied Housing Density 

Changes on Island Forests, 2000 to 2030

T

o assess the potential for increased housing 

development to occur on private forests, we 

constructed maps with geospatial data layers that 

represent: (1) projected housing density changes between 

2000 and 2030, (2) land ownership, and (3) land cover. 

We used geographic information systems (GIS) software 

to combine the data layers and identify private forest 

lands and projected housing density changes on those 

lands. Additional details on methods are provided in the 

appendix.

3

 A single family household is considered to be a unit, as is a 

single building with multiple households. Seasonal homes not 

occupied as primary residences are included in this analysis.

4

 64 units per square mile is roughly equivalent to 1 unit per 10 

acres; 16 units per square mile is roughly equivalent to 1 unit 

per 40 acres.

5

 This analysis is based on population and housing density 

data from Theobald (2005), which was based on the 2000 U.S. 

Census (Census Bureau 2001a–c) as a baseline; 2010 housing 

density data for the trust territories were not available at the 

time of this analysis.
and locations of urban areas. For American Samoa’s 

Tutuila island only, we also used methods described in 

Lim et al. (2010) to apply an elevation threshold to the 

housing density model to preclude development in areas 

above 100 meters (328 feet) elevation (see appendix for 

details).

Housing density projections for islands based on current 

models and data can be thrown off by unforeseen 

population shifts. Islands can experience variable 

population bubbles as people alternate between small 

and large islands depending on fluctuating circumstances 

such as changing climate or rising sea levels; global 

economies; and human needs related to jobs, health care 

or education.6 Because of their highly unpredictable 

nature, such irregular population fluxes over time were 

not factored into the islands housing density projection 

models.

Land Ownership and Forest Cover

Private forest ownership reflects a combination of data 

for land cover from various sources and ownership 

data from Theobald (2005). Forest land definitions 

for most islands varied by location, so local experts 

also were consulted to determine which land cover 

or vegetation categories in the data layers should be 

considered forest. For Hawaii, we used the LANDFIRE 

vegetation database (USDI and USDA 2013). For the 

Commonwealth of the Northern Mariana Islands, Guam, 

and American Samoa, we used vegetation layers mapped 

by satellite imagery compiled by the U.S. Department 

of Agriculture (USDA), Forest Service (Liu and Fischer 

2006a, 2006b, 2007). For Puerto Rico except Mona 

Island, we used the National Land Cover Data (NLCD) 

database (Homer et al. 2007, based on Kennaway and 

Helmer 2007); for Puerto Rico’s Mona Island, we used 

Martinuzzi et al. (2008). For the U.S. Virgin Islands, we 

obtained land cover from satellite imagery (Kennaway 

et al. 2008). See the appendix for more detail on how 

mapped categories were aggregated into forest or 

nonforest classes.

Forest Trends, Issues, and Priorities

Information about forest and population trends, forest 

resource issues, and priorities was largely gleaned from 

the 2010 statewide assessments of forest resources 

(known as “SWARS”) reports, which were created for 

each State, U.S. territory, and U.S.-affiliated island as a 

requirement of the 2008 Farm Bill (Food, Conservation, 

and Energy Act of 2008). The assessments identify 

priority forest issues and landscapes as the basis for 

developing a strategy across all ownerships to “conserve 

working forests, protect forests from harm, and enhance 

public benefits from trees and forests.” 

Mapping and Monitoring 

Island Land Cover

A consortium has been formed by Federal, State, 

and local governments to map land cover changes 

for certain Pacific islands and territories. The project 

uses geospatial technology and remote sensing 

data (such as high-resolution satellite imagery) 

to map island vegetation. Completed maps, data, 

and reports are shared with partners and made 

available to the general public. For details, visit the 

Pacific Southwest Region Web site at 

http://www.fs.usda.gov/detailfull/r5/forestgrasslandhealth/?cid=fsbdev3_046690&width=full.

6

 Personal communication from K. Friday, 2012, cooperative 

forester, U.S. Department of Agriculture, Forest Service 

Pacific Southwest Region and Pacific Southwest Research 

Station, State and Private Forestry.

Sayafe (Melochia villosissima var. compacta), a beautiful shrub 

found in Guam. Photo by Daniel W. Clark.
Hawaii

Molokai, Hawaii. Photo by Unclegene, istockphoto.com.

T

he Hawaiian Islands consist of eight large islands 

(Hawaii, Maui, Lanai, Molokai, Kahoolawe, Oahu, 

Kauai, and Niihau) and 124 small islands, reefs, 

and shoals. Located in the Pacific Ocean, more than 

2,000 miles from the nearest continent, the Hawaiian 

archipelago is among the most isolated places on the 

planet (USGS 2005). Hawaii is the only tropical island 

that is also a U.S. State.

Hawaii’s Forests and Population Trends

About 41 percent (1.7 million acres) of Hawaii’s land 

area is forest (Table 1); two-thirds of the forest land is 

considered native. About 46 percent of Hawaii’s forest is 

privately held, while most of the remainder is managed 

by the State (Gon 2006). 

Hawaii’s forests reflect its geological history and 

extreme climatic contrasts, which yield a wide range 

of ecosystems from subalpine forests, to lowland and 

montane rainforests, to mesic (moderately wet) forest, 

to lowland dry forests and coastal forests. The Hawaiian 

Islands contain more than two-thirds of the global life 

zones delineated by Holdridge (1947). On some islands, 

climatic gradients range from desert to rainforest to 

alpine communities in the span of fewer than 

20 miles (U.S. Forest Service 2011). The composition 

of most plant communities in Hawaii is determined 

by a combination of climate and elevation (Wagner et 

al. 1999). Tree species most common to Hawaii’s wet 

tropical forests include a myrtle (Myrtacae) species, 

Metrosideros polymorpha; and a legume (Fabaceae) 

species, Acacia koa. Other important plants include 
the tree fern Cibotium glaucum, and numerous species 

in the coffee family (Rubiaceae) such as Psychotria 

hawaiiensis and Coprosma spp.

This breadth of habitats supports some of the world’s 

most unique examples of tropical biodiversity, much of 

it endangered (Wagner et al. 1999) or found nowhere 

else on earth. Some 90 percent of Hawaii’s 10,000 native 

species of plants and animals are found only in the 

Hawaiian archipelago (U.S. Forest Service 2011). These 

extraordinary forests are sources of fresh water, forest 

products, recreational opportunities, and spiritual and 

cultural values as well.

Hawaii’s residents number about 1.4 million people 

(U.S. Census Bureau 2011a), 70 percent of whom 

live in Honolulu. The State’s population is estimated 

to have grown 12.3 percent between 2000 and 2010 

(U.S. Census Bureau 2011a). In Hawaii, 48 percent of 

all land is zoned for conservation, 47 percent is zoned 

agriculture, and 5 percent is zoned urban (Cannarella 

2010). However, urbanization is occurring at a rapid 

pace on most non-urban zoned lands across the State. 

This is particularly true of the island of Hawaii, where 

the 24 percent population increase from 2000 to 2010 

was the highest in the State (U.S. Census Bureau 2011a). 

On some smaller islands, human population tends 

to decrease over time as people move from smaller 

islands to larger ones in search of jobs, health care, and 

educational opportunities.7

Native Psychotria hawaiiensis, Hawaii Island, Hawaii. Photo by 

J.B. Friday.

As seen in this view above Honolulu, Oahu, Hawaii’s lowland wet forests are almost gone, in part due to development. 

Photo by J.B. Friday.

7

 Personal communication from R.J. Cannarella, 2012, 

forester, Hawaii Department of Land and Natural Resources, 

Division of Forestry and Wildlife Planning and Information 

Services.
Hawaii’s lowland wet forests are almost gone, with 

many of the last remaining patches found on the eastern, 

windward sides of the largest islands (Zimmerman et 

al. 2008). More than 90 percent of dryland forests in 

Hawaii have also been lost, primarily to conversion 

for pasture, spread of invasive species, and increased 

wildfire (Bruegmann 1996). The remaining fragments 

of dry forest—which contain more than 25 percent 

of Hawaii’s threatened and endangered species—are 

heavily degraded by deforestation, land development, 

fire, over-grazing, and invasive plant species such as 

fountain grass (Pennisetum setaceum), which is capable 

of carrying fire into areas not usually prone to fires 

(Cabin et al. 2000). 

Conversion of forest lands to nonnative ecosystems is 

perhaps the greatest threat to Hawaii’s dry forests, rather 

than direct loss of forest cover to housing development; 

many agricultural subdivisions are well-managed, and 

stringent zoning laws help mitigate direct impacts from 

development and urbanization.7

Montane wet forests are currently the most healthy 

native ecosystem and are the only forests to harbor 

significant populations of Hawaii’s rare native avifauna. 

However, these forests also are pressured at higher 

elevations by nonnative pasture grasses and at lower 

elevations from lowland invasive woody species.

Forest Resource Issues and Priorities

• Invasive species

The introduction and spread of invasive nonnative 

species of plants and animals—including weeds, 

insects, pathogens, and vertebrate animals—

dominate Hawaii’s forest resource issues (U.S. 

Forest Service 2011). More than 300 native 

Hawaiian species are known to be extinct; these 

include more than 50 percent of all native birds, 

more than 60 percent of snails, and more than 10 

percent of all of the known flora (Wagner et al. 

1999). All of the archipelago’s imperiled plants and 

birds are threatened by nonnative species (Wilcove 

et al. 1998). Even in places where human population 

has decreased, particularly on smaller islands, 

invasive species introduced by former residents may 

be invading and spreading now because of lack of 

management when people move out.8

8

 Personal communication from S. Mann, 2012, forestry 

program manager, Hawaii Department of Land and Natural 

Resources, Division of Forestry and Wildlife.

Endangered by Invasive Species

Hawaii comprises only 0.2 percent of the 

Nation’s land mass but contains 30 percent 

of the Nation’s federally listed endangered 

species (Cannarella 2010). Loss of habitat 

due to impacts from invasive species is one 

of the principal factors affecting the 437 plant 

and animal threatened or endangered species 

in Hawaii (U.S. Fish and Wildlife Serv. 2012). 

Invasives can be rapidly introduced and spread 

by housing development and related activities. 

Conversion to nonnative species in Hawaii 

typically follows disturbance such as clearing 

for agriculture or urban development. Human 

modification of habitats in Hawaii is primarily 

responsible for the distribution of several 

plant weeds that have become widespread 

on degraded lands, such as strawberry guava 

(Psidium cattleianum), albizia (Falcataria 

moluccana), and Christmasberry (Schinus 

terebrinthifolius).

Federally endangered Hawaiian crow or 'Alala 

(Corvus hawaiiensis). Photo by Daniel W. Clark.
10

All of Hawaii’s imperiled plants, birds, and some other animals, such as this rare Oahu tree snail (Achatinella curta) and 

endangered Kokio (Kokia drynarioides) are threatened by nonnative species. Photos by Daniel W. Clark.

• Water quality and quantity

“In Hawaii, the most valuable product of the forest 

is water, rather than wood” (Cannarella 2010). Water 

quality and quantity are being significantly affected 

by human activities and land use changes such as 

urbanization and diversion of water for increasing 

urban populations, complicated by wildfire, 

pollutants, and invasive species (Cannarella 2010). 

• Wildfire

Most native species in Hawaii evolved without fire 

and do not recover well after wildfires (Canarella 

2010). Over the past century, human-induced 

changes to ecosystems and human-caused ignitions 

have led to increased wildfire frequency and size 

(Cordell, no date; LaRosa et al. 2008). Throughout 

the State, the average acreage burned increased 

fivefold and the average number of fires increased 

sixfold from the early (1904-1939) to the mid (1940-

1976) part of the 20th century (Cuddihy and Stone 

1990). In particular, a serious grass-fire cycle has 

become established; introduced plants, particularly 

grasses, are often more fire-adapted than native 

species and are able to invade numerous habitats 

after a fire, further increasing the frequency and/or 

intensity of fires (Cannarella 2010; Cordell, no date). 

Erosion, particularly on steep-sided watersheds, is 

increasing as a consequence of fire, further reducing 

the integrity and biodiversity of Hawaii’s watersheds 

(Cannarella 2010). 

• Urban and community forestry

Hawaii’s urban forest has a mixture of young and 

mature canopies, and some newer urban areas have 

few or no trees. Frequent tree damage problems 

include topping, trimming, and poisoning of street 

trees; dumping of hot charcoal at the base of park 

trees; and asphalt or concrete proximity damage to 

root systems, among other impacts of urbanization 

(Cannarella 2010).

Prescribed burns, as seen here in Oahu, are used to prevent 

damage to forests and native species from wildfire. Photo by 

U.S. Army Garrison-Hawaii, Flickr.
11

Frequent urban tree damage includes topping, trimming, 

vandalism, and poisoning of street trees. Photo by Angelina 

Earley, Flickr.

Development Projections

About 8 percent (~ 65,000 acres) of Hawaii’s private 

forest land is projected to experience a substantial 

increase in housing density from 2000 to 2030, such that 

9

 Personal communication from J.B. Friday, 2012. Extension 

forester, University of Hawaii at Manoa, College of Tropical 

Agriculture and Human Resources.

the category will shift from very rural (rural I) to less 

rural (rural II) or to urban-exurban (Fig. 1). Substantial 

housing increases are projected for localized areas of 

each of Hawaii’s five largest islands. Most of these areas 

are located close to or just inland of coastal areas and 

include the windward (wet) coast on the Island of Oahu; 

the Puna, Hilo, and Hamakua districts on the Island of 

Hawaii; the east end of Molokai; and the north shore 

region of Kauai. Almost all the native wet forest at 

risk from housing development is in the Puna District.9

Development increases are also projected for the leeward 

(dry) coastal areas. However, the impact of this leeward 

development on forests should be minimal because 

these areas have been largely deforested for more than a 

century.9 

Montane wet forests, such as this forest on Kauai’s Mount Waialeale, are the healthiest native ecosystem found in Hawaii. Photo 

by Sheri Mann, State of Hawaii, Department of Land & Natural Resources.
12

Figure 1.—Maps show projected housing density change on private forest land in Hawaii between 2000 and 2030 along with public 

forest and nonforest areas. Pie chart reflects the percentage of private forest land area in each of the mapped change classes.

Hawaii

Projected Housing Density Change 

on Private Forest land (2000 to 2030)

Increase: rural 1 or rural 2 to urban/exurban

Increase: rural 1 to rural 2

No change: rural 1 or rural 2

No change: urban/exurban

Nonforest

Public forest

5% 3%

68%

24%

68%

24%

3% 5%
13

Case Study

Gall Wasps, Be Gone! 

The End is Near for an Invasive Species in Hawaii

Hawaii has reason to celebrate a stunning success in 

combating invasive species through “biocontrol”—the 

use of host-specific natural enemies in weed or pest 

management. 

The gall wasp, Quadrastichus erythrinae, has plagued 

Hawaii since 2005 and has had extremely adverse effects 

on the State’s native tree, Erythrina sandwicensis, 

also known as coral tree or tiger’s claw, as well as an 

introduced ornamental tiger’s claw tree, Erythrina 

variegata. Thousands of trees had died off: “We really 

had the possibility of losing one of our native trees,” 

explained Hawaii State Entomologist Neil Reimer in 

an interview with The Maui News in 2010 (Dingeman 

2010). 

Eurytoma erythrinae to the rescue! This African wasp is 

a natural predator of the gall wasp and was distributed 

widely in Hawaii beginning in 2008, with immediate 

impact (Heu et al. 2008). The predatory African wasps 

easily overcame the destructive gall wasp population, 

and the native tiger’s claw trees began to recover. By 

2010, Reimer remarked that the gall wasp “is not coming 

back” (Dingeman 2010).

The use of biocontrol strategies promises to be a 

sustainable way to control the damaging effects of 

invasive species in the Pacific Island region. For more 

information visit 

http://www.spc.int/en/about-spc/members.html.

Additional sources: J.B. Friday (see footnote 9); Hawaii 

Dept. of Agric. 2008; Secretariat Pacific Community 2010

Gall wasp damage on Indian coralbean (Erythrina variegata L.). Photo by 

Albert Mayfield, U.S. Forest Service, Bugwood.org.
14

Flat limestone plateau with abrupt cliffs dropping to the ocean in Guam. Photo by U.S. Forest Service, Pacific Southwest Region, 

State & Private Forestry.

Guam

L

ocated in the north Pacific Ocean, about threequarters of the way from Hawaii to the Philippines, 

Guam has a tropical marine climate, with a distinct 

dry season January to June. The northern half of the 

island is flat limestone plateau with abrupt cliffs 

dropping to the ocean; the southern portion has rolling 

to mountainous terrain and deeply weathered volcanic 

soils (Donnegan et al. 2004a, Mafnas 2010), where 

numerous watersheds are drained by 96 rivers (Mafnas 

2010). Guam is surrounded by a species-rich reef system 

supporting more than 5,000 marine species (Mafnas 

2010). 

Guam’s Forests and Population Trends

About 48 percent (~ 64,000 acres) of Guam’s 134,000 

land acres are forested (Liu and Fischer 2006b); some 

69 percent (~ 44,000 acres) of forest land is privately 

owned (Table 1). Approximately 18 to 20 percent of 

Guam is urban or developed land (Donnegan et al. 

2004a, Mafnas 2010), including roads, towns, airstrips, 

and military facilities. 

Nearly three-quarters of Guam’s forest is a limestone 

forest type, supporting such species as breadfruit 

(Artocarpus mariannensis), banyan (Ficus prolixa), 

aggag (Pandanus tectoris), and an open scrub-forest 

found on steep slopes and cliffs dominated by Cordia 

subcordata. Volcanic forests on the southern portion 

of the island are vegetated with a mix of grassland and 

patchy forest; the forest tends to follow river drainages, 

ravines, and other topographic features. Common ravine 

forest trees include pugua (Areca catechu), banyan, pago 

14
15

(Hibiscus tiliaceus), aggag, and other species including 

the introduced and now widespread tangan tangan 

(Leucaena leucocephala). Areas of swamp, mangrove, 

and marsh are also found on Guam. Trees tend to be 

relatively small (5- to 10-inch diameter) owing to 

disturbance by typhoons, human land use practices, 

invasive weeds and insects, and historical timber harvest 

(Donnegan et al. 2004a). Pure examples of Guam 

forest types are now rare, and the forests tend to be 

mixtures with dense, low thickets of secondary species 

predominating (Donnegan et al. 2004a, Mafnas 2010).

The population of Guam in 2010 was around 159,000, 

an increase of nearly 3 percent from the 2000 Census 

population (Census Bureau 2011c) and nearly triple 

what the population was in 1960 (Mafnas 2010). Guam 

faces a substantial increase in temporary and permanent 

population—to more than 250,000 people—associated 

with a proposed U.S. military buildup expected by 2014 

(Mafnas 2010, Marler and Moore 2011, U.S. Dept. of 

Defense 2010). 

Since Western colonization in the 16th century, Guam 

has changed from a mostly forested environment to a 

highly fragmented landscape, especially in the south, 

where older forests are generally restricted to ravines, 

The breadfruit (Artocarpus mariannensis) found in Guam’s 

agroforests is an important staple crop. Photo by EhPoint, 

istockphoto.com.

Sella Bay, Guam. Photo by Jonesee02, istockphoto.com.

valley bottoms, and on steep slopes (Mafnas 2010). 

Although total amount of forest cover has been relatively 

constant since the 1950s, the condition of the forest has 

declined owing to urban development, storm damage, 

wind, fire, and other factors. The urban landscape—with 

increasing urbanized zones and associated roads, 

shopping centers, and parking lots—has expanded 

markedly into some forested areas (Mafnas 2010). 

Guam urbanization. Photo by U.S. Forest Service, Pacific 

Southwest Region, State & Private Forestry, Flickr.
16

Since western colonization, Guam has changed from a mostly forested environment to a highly fragmented landscape. Photo by 

ziggy_mars, istockphoto.com.

Forest Resource Issues and Priorities

• Invasive species and feral animals

Introduction of nonnative species and diseases has 

resulted in the loss of 9 of the 12 bird species that 

once made up the entire native avian community 

of Guam (U.S. Fish and Wildlife Ser. 2012). 

Development (including shipping of construction 

materials and landscaping plants and other activities) 

is contributing to the introduction and spread of 

invasive species—notably the Asian cycad scale 

(Aulacaspis yasumatsui), the coconut rhinoceros 

beetle (Oryctes rhinoceros), and numerous fungi 

and bacteria—thus altering forest structure, 

composition, and resilience to other disturbance 

processes (Mafnas 2010, Marler and Moore 2011). 

Development has also helped introduce feral 

animals including deer, pigs, and snakes, which can 

clear forest floors or damage trees (Strieker 1998). 

Perhaps more destructive than all developmentrelated invasive species combined, however, has 

been the introduction and spread of the brown tree 

snake (Boiga irregularis), which is widely regarded 

as the major factor affecting Guam’s birds.9

• Wildfire

Wildfires, mostly human-caused, are a major cause 

of upland degradation and deforestation on Guam, 

threatening existing forests and interfering with 

the establishment and expansion of native forests 

(Mafnas 2010). A severe grass-fire cycle is affecting 

Guam’s dry forests and shrubland, in which invasion 

of flammable nonnative grasses increases fine fuel 

loads and increases the likelihood of fire ignition 

and spread; fire further kills the native vegetation, 

the grasslands expand every year, and native forest 

decreases (Cordell, no date; J.B. Friday9 ). When fire 

removes the grass cover, subsequent rains can cause 

severe erosion.9
17

Cycas micronesica: Ancient Species 

Threatened by Hitchhiking Insects

Believed to be the oldest of the seed-bearing plants, 

cycads can help us better understand the biology of 

many plant species, as well as links between human 

disease and environmental toxins (Marler et al. 2007). 

Only a few cycad species still exist. One cycad found 

only on Guam and other Marianas Islands, Cycas 

micronesicais—known locally as fadang—is rapidly 

diminishing in numbers, owing in part to introduced 

invasive insects that have hitchhiked to the island on 

cycads imported from Hawaii for landscaping (Smith 

2007, Terry and Marler 2005). Among the introduced 

Fadang (Cycas micronesica), one of Guam’s rare and endangered species. Photo by 

Daniel W. Clark.

pests is the Asian cycad scale, Aulacaspis yasumatsui, 

which was first found in urban plantings on Guam in 

2003 (Smith 2007, Terry and Marler 2005) and now 

threatens the survival of a once dominant forest plant 

on Guam (Marler et al. 2007). With no known natural 

enemies on the island and a climate that favors the 

insect’s rapid reproduction and widespread distribution 

(Smith 2007), the scales cover and devour cycad leaves, 

cones, and developing seeds; a mature plant can die 

within a year of infestation (Terry and Marler 2005). 

The “epidemic mortality” in the Guam population of 

C. micronesica has prompted urgent conservation 

efforts (Marler et al. 2007).

The brown tree snake (Boiga irregularis) near a trap and up close. Photos by USDA, APHIS.
18

• Water quality and supply

Removal of forest vegetation for road construction, 

off-road vehicle use, and building sites is 

contributing to increased erosion and degraded water 

quality. Water resources on the island vary based on 

the distinctive geologies of northern and southern 

Guam; eroded sediment—which can adversely 

affect water quality, aquatic habitat, and reef 

communities—is of particular concern in the south 

of the island (Mafnas 2010). 

• Forest conversion

Although direct impact from increased housing 

density is not the major factor driving conversion 

of forest land on Guam10, proposed housing 

development and other activities related to the 

military buildup alone is expected to directly remove 

about 5,000 forested acres, about 9 percent of 

Guam’s total forested area, by 2014 (Mafnas 2010). 

Impacts on Guam’s forest recreation resources in 

the affected areas are expected to be substantial, 

along with impacts on local archaeological sites and 

water quality (Marler and Moore 2011, U.S. Dept. 

of Defense 2010). Loss of such extensive forest 

cover will not only affect the viability of Guam’s 

forests but is also likely to increase the threats from 

invasive species and wildfire (Mafnas 2010).

10 Personal communication from J. Lawrence, 2012, U.S. 

Department of Agriculture, Natural Resources Conservation 

Service, Pacific Islands Area-West.

Development Projections

About 25 percent (~ 11,000 acres) of Guam’s private 

forest land is projected to experience a substantial 

increase in housing density from 2000 to 2030, such 

that the category will shift from very rural (rural I) to 

less rural (rural II) or to urban-exurban11 (Fig. 2). These 

housing density increases are projected to occur in 

localized areas across Guam, and particularly within 

about 2 miles of the coastline. Notable areas for such 

development include coastal areas north of Inarajan, 

as well as several areas along the coast and just inland 

between Pago Bay and Pagat point. 

11 The housing density projections used for this report 

(Theobald 2005) are based on past population trends and 

do not reflect the expected increase in population due to the 

military build-up.

Forests are critical to Guam’s water supply. Photo by Leksele, 

istockphoto.com.

Forest conversion in Guam. Photo by U.S. Forest Service, Pacific 

Southwest Region, State & Private Forestry, Flickr.
19

Figure 2.—Maps show projected housing density change on private forest land in Guam between 2000 and 2030 along with public 

forest and nonforest areas. Pie chart reflects the percentage of private forest land area in each of the mapped change classes.

Guam

Projected Housing Density Change 

on Private Forest land (2000 to 2030)

Increase: rural 1 or rural 2 to urban/exurban

Increase: rural 1 to rural 2

No change: rural 1 or rural 2

No change: urban/exurban

Nonforest

Public forest

22%

3%

29%

45%

22%

3%

29%

45%
20

Case Study

A Pig Derby, Young Champions, 

and the Micronesia Challenge in Guam

The first ever pig derby, held in Guam in 2012, 

creatively wove together key elements of what is 

called the “Micronesia Challenge” to involve youth 

and citizens in the conservation of island marine and 

terrestrial resources.

The Challenge—a pledge among five Pacific island 

governments, including Guam and CNMI—was 

launched in 2006 to conserve at least 30 percent of 

the near-shore marine resources and 20 percent of the 

terrestrial resources across Micronesia by 2020. Included 

in the Challenge is a Young Champions of Micronesia 

Challenge program, which has enthusiastically 

mentored more than 20 local youth in issues of resource 

conservation.

Young Champions blog about issues related to marine 

and terrestrial resources and participate in educational 

outreach to other students and the community. They 

also participated in and helped to facilitate the 2012 Pig 

Derby, hosted by the Guam Department of Agriculture 

and the Guam Coastal Management Program. The 

derby’s goal was to use celebration and education to 

raise awareness about the feral pig population, which 

is contributing to erosion and the destruction of native 

forests.

Christine Camacho of the Guam Coastal Management 

Program explained the purpose of the event: “The earth 

month 2012 pig derby is inspired by going local. We 

want to combat invasive species and at the same time 

celebrate our uses of pig within our culture so the pig 

derby itself will be followed by a pig cook off” (Ridgell 

2012). All licensed hunters were welcomed to participate 

in hunting the feral pigs of the island over 2 days. 

Numerous pigs were hunted and community capacity 

was enhanced as the people of Guam came together 

to address an issue that has far-reaching effects on the 

island’s ecosystem. 

In addition to raising awareness among its youth, Guam 

has achieved remarkable progress toward the overall 

Challenge goal. As of 2011, Guam had protected 

some 13 percent of marine resources and 23 percent 

of terrestrial resources. The program on Guam, with 

its unique approach, continues to grow as citizens of 

all ages directly address ecological issues through 

restoration of native plant species and other activities. 

Additional sources: 

Global Island Partnership Website: 

https://www.cbd.int/island/glispa.shtml 

Micronesia Challenge Website: 

http://themicronesiachallenge.blogspot.com/p/about.html

Feral pig. Photo by USDA, Flickr.
21

American Samoa

Pago Pago Harbor in the distance, American Samoa. Photo by Bruce C. Johnson, Jr., Flickr.

A

merican Samoa, part of a larger group of islands 

known as the Samoan archipelago, is the only U.S. 

territory south of the equator. Located in the South 

Pacific Ocean, about half way between Hawaii and New 

Zealand, America Samoa is a group of five inhabited 

volcanic islands (Tutuila, Aunu’u, Ofu, Olosega, and 

Ta’u) and two remote atolls (Rose, Swains). The main 

islands of American Samoa are steep mountains that 

emerge from about 2 to 3 miles below the sea surface 

(Craig 2002). The climate is hot, wet, and humid, with 

an annual rainfall of about 129 inches at the airport 

on Tutuila and more than 200 inches in the mountains 

(American Samoa Community College 2010, Craig 

2002).

American Samoa’s Forests and Population Trends

American Samoa’s total land area is about 48,000 acres; 

about half of the land (~ 24,000 acres) is forest cover, 

85 percent of which is privately owned (Table 1); most 

private land is held communally by the church, by 

extended families, or individually by “freehold” owners 

(American Samoa Community College 2010). Even 

the National Park of American Samoa—which covers 

about 13 percent of the territory’s land area—is not 

owned by the Federal Government but was established 

on communal land under a 50-year lease agreement 

between the National Park Service and a local group, 

which retains ownership of the land (American Samoa 

21
22

Community College 2010). Some 7 percent of American 

Samoa is classified as urban, generally in areas where 

lowland rain forest previously existed (Donnegan et al. 

2004b). 

Owing to the warm temperature and year-round 

rainfall, the natural vegetation of American Samoa 

is tropical rainforest; native forests extend from the 

seashore to the mountain peaks (American Samoa 

Community College 2010). Forest types include lowland 

rainforest—found on ridges, slopes, in valleys, and on 

lowland lava flows—which supports tree species such 

as tava, or island lychee (Pometia pinnata); asi toa, or 

Malaysian apple (Syzygium inophylloides); and tamanu 

(Calophyllum neo-ebudicum). Montane rainforest is 

high-elevation, often steeply sloped forest (greater 

than 1,640 feet) characterized by high precipitation; 

the dominant canopy species is the native and endemic 

maota mea, or rose mahogany (Dysoxylum huntii Merr. 

ex Setchell) (Donnegan et al. 2004b). Cloud forest 

and scrub are limited to the highest elevations on Ta’u 

and Olosega, in areas generally blanketed by clouds 

and mist; this forest type is cooler and wetter than 

montane rain forest and is dominated by tree ferns and 

the endemic Reynoldsia pleiosperma (Donnegan et al. 

2004b).

Along the undisturbed coastal areas, a narrow strip of 

littoral forest helps stabilize coastal areas, protects soils 

from erosion, filters water runoff, and provides habitat 

for numerous wildlife species including flying foxes, 

seabirds, and nesting sea turtles (American Samoa 

Community College 2010, Donnegan et al. 2004b). 

Mangrove forest, valuable as a storm buffer and water 

filter, occurs along coastal areas on only two islands, 

Tutuila and Aunu’u, particularly in sheltered lagoons 

and protected estuaries (American Samoa Community 

College 2010, (Donnegan et al. 2004b). American 

Samoa also contains about 3,106 acres of urban forests, 

concentrated in and around villages on the southwest 

lowland plains of Tutuila (American Samoa Community 

College 2010).

The current population (~ 56,000 in 2010) represents 

a decrease of about 3 percent from the 2000 Census 

population (Census Bureau 2011b). However, prior to 

2000, the population had been growing at 2.1 percent per 

year, 96 percent living on Tutuila (Craig 2002). Urban 

lands expanded from 5 percent of the total land area 

to 7 percent from 1985 through 2001 (Donnegan et al. 

2004b). 

To’ito’i and fasa native coastal scrub forest, Tutuila, American Samoa. Photo by J.B. Friday.
23

American Samoa still possesses some of the most 

pristine and intact forests in the South Pacific, but 

these forests and their biodiversity are at risk of being 

degraded or lost (American Samoa Community College 

2010). Important forest habitats have been cleared and 

replaced by agriculture and development, primarily on 

the lower, gentler slopes as well as in upland rain forest 

where soils permit agricultural use. Forest land declined 

by about 3 percent between 1985 and 2001 (Donnegan 

et al. 2004b), and of the 40 acres of lowland lava flow 

rainforest identified in 2002, only 28 acres remain, 

representing a 30 percent decrease in less than a decade 

(American Samoa Community College 2010). Mangrove 

forests declined by 18 percent during that same period 

(Donnegan et al. 2004b), and a 2009 study estimated 

that only about 89 acres of mangrove forest remain 

out of 122 acres identified in 2003 (American Samoa 

Community College 2010). 

Forest Species—Big Relationships 

on Small Islands

American Samoa’s forests support fewer than 

500 native flowering plant species and ferns, 

about 44 bird species, and only 3 mammal 

species, all bats. Although few in number, these 

island species have exceptional ecological 

value. Nearly 30 percent of Samoa’s flowering 

plants are found nowhere else outside the 

Samoan archipelago, and five of these exist only 

on American Samoa. Consequently, forest plants 

and wildlife are highly dependent on each other. 

The rare “mamuma” or many-colored fruit dove, 

for example, eats fruit from forest trees such 

as the native banyan, for which the bird is an 

important pollinator and seed disperser. Only a 

few banyan trees remain on the Tafuna Plain on 

Tutuila, and they are vulnerable to removal for 

increasing development. 

—Source: Craig 2002

Flying fox (Pteropus samoensis). Photo by 

Daniel W. Clark. 

More than 80 percent of American Samoa’s forests are 

privately owned. Photo by LisaInGlasses/istockphoto.com.
24

Forest Resource Issues and Priorities

• Invasive species and feral animals

Among the greatest risks to American Samoa’s 

native rainforest—even areas too remote or steep 

to be cultivated or developed—is the spread of 

exotic invasive plants. Forests are also affected by 

introduced pigs, which are spreading invasive plants, 

damaging understory vegetation, and destroying 

riparian areas (American Samoa Community College 

2010). 

• Water quality and quantity

As forests have been cleared for agriculture and 

development, the water flow into streams is 

increasing, washing large amounts of exposed 

unstable soil—including agricultural fertilizers and 

pollutants—into streams, which flow onto coral 

reefs. These effects are intensified by American 

Samoa’s rugged topography and high frequency and 

intensity of rainfall year round. Further, American 

Samoan wetlands are threatened by filling for 

development (American Samoa Community College 

2010).

• Sustainability of urban forests

Scarcity of flat land suitable for building has resulted 

in the replacement of urban forests by structures and 

roads. Exotic plants imported for urban landscapes 

have invaded some of the remaining urban forest, 

along with insects and diseases that are affecting 

nonnative plants (American Samoa Community 

College 2010).

False kava (Piper auritum), Tutuila, American Samoa, 

resembles kava (Piper methysticum) but is difficult to control 

and outcompetes true kava plants. Photo by J.B. Friday.

Forests have been cleared for agriculture, such as this taro 

field, which results in washing large amounts of exposed 

unstable soil—including agricultural fertilizers and pollutants—

into streams and eventually coral reefs. Photo by tropical.pete, 

Flickr.

Development Projections

About 3 percent (~700 acres) of American Samoa’s 

private forest land is projected to experience a 

substantial increase in housing density from 2000 to 

2030, such that the category will shift from very rural 

(rural I) to less rural (rural II) or to urban-exurban 

(Fig. 3). Substantial housing increases are projected to 

occur in some rural private forests along the northern 

coastline of Tutuila where elevation is below about 

300 feet (see appendix), and in a few scattered areas 

near existing population bases with established roads. 

The Tafuna Plain of Tutuila also is likely to undergo 

development and consequent changes to tree cover9; 

however, our dataset classifies that area as agricultural 

or urban and therefore was considered nonforest for this 

analysis. 
25

Figure 3.—Maps show projected housing density change on private forest land in American Samoa between 2000 and 2030 along 

with public forest and nonforest areas. Pie chart reflects the percentage of private forest land area in each of the mapped change 

classes. The “Increase: rural 1 to rural 2” category (orange) does not appear on the pie chart because the corresponding value, 

0.2%, is too small to be visible.

American Samoa

Projected Housing Density Change 

on Private Forest land (2000 to 2030)

Increase: rural 1 or rural 2 to urban/exurban

Increase: rural 1 to rural 2

No change: rural 1 or rural 2

No change: urban/exurban

Nonforest

Public forest

3% 0.2%

74%

22%

3% 0.2%

74%

22%
26

Case Study

Healthy Seedlings for Healthy Forests: 

Workshop in American Samoa 

Tree seedling nurseries don’t always get acknowledged 

as critical components of any conservation or restoration 

effort. In July 2012, Diane Haase, western nursery 

specialist for the U.S. Forest Service, and J.B. Friday 

from the University of Hawaii Forestry Extension, 

conducted a week-long nursery training workshop in 

American Samoa. The workshop focused on enhancing 

the ability of the nursery at American Samoa Community 

College—the sole source of seedlings for urban and rural 

forestry restoration on the island—to produce healthy 

seedlings for reforestation, native forest restoration, 

agroforestry, riparian/coastal land stabilization, and 

urban beautification.

About 25 people attended the workshop, expressing 

individual goals that included:

• Learning more to help the community 

• Applying new information to seedling production 

and “out-planting” practices (the planting of 

seedlings raised in a greenhouse or nursery into the 

field) 

• Growing healthy plants locally rather than importing 

them from off-island

As a result of the workshop, American Samoan forestry 

staff members have a stronger understanding of 

plant production technology, which they can apply to 

future nursery production. The workshop also offered 

opportunities for the organizers to interact with forestry 

greenhouse staff and learn more themselves about the 

culture and environmental habitats of American Samoa.

—Source: Haase 2012

Forestry program staff at a field site where plants have been 

out-planted from the nursery. Photo by Diane Haase.

Forest Service nursery specialist Diane Haase (right) 

demonstrates testing procedures for nursery growing media. 

Photo by J.B. Friday.
27

Bird Island Marine Protected Area, Saipan. Photo by Daniel W. Clark.

Commonwealth of the Northern Mariana Islands

T

he Commonwealth of the Northern Mariana Islands 

(CNMI) is a chain of 14 volcanic and limestone 

islands located in the Pacific Ocean, about threequarters of the way between Hawaii and the Philippines 

(U.S. CIA 2010). The warm and humid climate is 

marked by moderate trade winds and little seasonal 

variation (Liu and Fischer 2006a, U.S. CIA 2011). Most 

soils on the three largest islands of Saipan, Rota, and 

Tinian are limestone, while a small portion of soils on 

the northern islands are volcanic (Com. North. Mariana 

Is. For. (CNMI) 2010, U.S. CIA 2010).

CNMI’s Forests and Population Trends

CNMI has a land area of about 75,000 acres, 67 percent 

(~ 50,000 acres) of which is forested; some 78 percent 

of CNMI forest land is privately owned (Table 1). 

The original native forests of these islands were 

mixed, including dry season deciduous forest on lower 

limestone terraces and moist forest on higher terraces 

(CNMI Forestry 2010). 

The most intact and extensive primary forests in the 

Commonwealth are found on the island of Rota, while 

native forests on the islands of Saipan and Tinian have 

largely been replaced by plantations (Acacia and sugar 

cane) and secondary forest (CNMI Forestry 2010, Liu 

and Fischer 2006a). On Saipan, remaining native forest 

occurs only in small isolated fragments on steep slopes 

on low elevations and in higher elevation conservation 

areas (Gillespie n.d.). 

27
28

Contemporary forests are a mixture of native and 

nonnative species, primarily in smaller tree size classes, 

with intact fragments of native limestone and ravine 

forest (Donnegan et al. 2011). Native limestone forests, 

while not pristine, contain relatively high numbers of 

native species including kafir lime (Citrius hystrix), 

Hawaiian screwpine (Pandamus tectorius), and the 

endemic shrub Guamia mariannae. Ravine forest 

vegetation—found on the southernmost part of Rota 

where the volcanic core has weathered into highly 

dissected and sheltered ravines—is primarily swordgrass 

(Miscanthus floridulus) savanna mixed with shrubs and 

trees such as betel nut (Areca catechu) and breadfruit 

(Artocarpus altilis). Common nonnative species found 

in mixed native/nonnative forests include tangan tangan 

or white leadtree (Leucaena leucocephala), cynometra 

(Cynometra ramiflora), and banyan or strangling fig 

(Ficus prolixa). 

Saipan is the largest island (~ 29,000 acres) and 

supports about 48,000 people (Census Bureau 2011d). 

About 5,500 people live on Rota (~ 20,000 acres) and 

Tinian (~ 25,000 acres) (CNMI Forestry 2010, Census 

Bureau 2011d). An expanding tourist market spurred 

construction and manufacturing industries between 

1980 and 1997, when CNMI’s population nearly 

quadrupled, from 16,780 to 63,000 (U.S. EPA 2008). 

That development boom resulted in an escalation in 

housing starts and the construction of many hotels, 

resorts, apartments, golf courses, and commercial 

businesses (U.S. Environ. Prot. Agenc. 2008), with the 

population peaking in 2000 at 69,221 (Census Bureau 

2011d). However, the 2010 Census revealed a population 

of about 53,500 people, a 22 percent decrease from 

2000, apparently due to declining tourism and loss of 

manufacturing industries (CNMI Forestry 2010, Census 

Bureau 2011d). 

Native vegetation of CNMI has been conspicuously 

altered in large part by a long history of human 

occupation and agricultural activities, and by climatic 

disturbance (Donnegan et al. 201l). Saipan and Tinian 

in particular experienced significant forest destruction 

during World War II, followed by commercial and 

residential development (CNMI Forestry 2010). After 

World War II, the islands were aerially seeded with the 

fast-growing leguminous tree, Leucaena leucocephala

(CNMI Forestry 2010), which is now widespread and 

self-perpetuating (Donnegan et al. 2011). In the 1980s, 

overall, the islands were still largely forested, although 

native forests common to the natural limestone was 

dominant only on Rota; Saipan and Tinian were largely 

occupied by introduced tree species and secondary 

vegetation (Liu and Fischer 2006a). 

In recent decades, the most important land use changes 

have involved rapid conversion of forests to agriculture 

and urban uses; between the late 1970s and early 

2000s, the Northern Mariana Islands lost 6 to 7 percent 

of its forest cover (Donnegan et al. 2011). Despite 

recent population and economic downturns, the three 

most populated islands of CNMI are still said to be 

experiencing heavy pressure on remaining lands from 

“massive expansion and construction of the urban areas” 

(CNMI Forestry 2010). 

SongSong village, Rota, CNMI. Photo by Michael Lusk, Flickr.
29

Forest Resource Issues and Priorities

• Water quality and quantity

In some areas of CNMI, there is either too little 

or too much water. On Saipan, for example, water 

shortages (and incursions of salt water into the 

water supply) are related to urban development 

in watersheds and over-pumping from existing 

wells. Other areas of Saipan are subject to flooding 

during heavy rainstorms and typhoons, due in part 

to development in natural floodplains, removal of 

vegetation, and construction of buildings that affect 

runoff (CNMI Forestry 2010). 

• Invasive Species

Currently the scarlet gourd (Coccinia grandis) is 

the most invasive and serious threat to the health 

of CNMI forests, particularly scrub forest; a recent 

introduction (early 1990s), the scarlet gourd has 

spread to more than 80 percent of Saipan. As on 

other Pacific islands, coconut rhinoceros beetle 

(Oryctes rhinoceros) and Asian cycad scale 

(Aulacaspis yasumatsui) are also invasive threats 

(CNMI Forestry 2010). In the northern islands, feral 

animals such as goats, pigs, and cows have denuded 

large expanses of the forest (CNMI Forestry 

2010). Weedy vines are beginning to smother the 

forest canopy throughout the Northern Marianas 

(Donnegan et al. 2011). Rainwater collectors, like this one in Saipan, are important for 

those times when there is insufficient ground water. Photo by 

Tropical.pete, Flickr.

• Wildfire

Wildfires are common in CNMI; repeated fires 

on steep slopes contribute to soil erosion and loss 

of wildlife habitats (CNMI Forestry 2010). Local 

forestry and fire officials anticipate an increase in 

wildland fire incidence and activities in coming 

years due to changing weather patterns and 

relocation of homes into areas identified as at-risk 

for wildfire (CNMI Forestry 2010). In savanna areas 

people regularly ignite fires, which can kill tree 

seedlings, spread into forested areas, and leave soils 

exposed to erosion and movement (Donnegan et al. 

The invasive coconut rhinoceros beetle (Oryctes rhinoceros 2011). ) 

is responsible for destroying palm species in CNMI and other 

Pacific islands. Photo by Rein De Keyser, Flickr.
30

Development Projections

About 19 percent (~ 7,600 acres) of CNMI’s private 

forest land is projected to experience a substantial 

increase in housing density from 2000 to 2030, such 

that the category will shift from very rural (rural I) to 

less rural (rural II) or to urban-exurban (Fig. 4). Forests 

expected to undergo this change are in localized areas, 

most notably, on Saipan, on a swath of land stretching 

from Laulau Beach to Marine Beach, and in places to 

the north and west. Housing density is also projected to 

increase on Tinian (west of the airport) and on Rota, east 

of the airport and on a strip of coastal land located in the 

southwest. 

Figure 4.—Maps show projected housing density change on private forest land in Commonwealth of the Northern Mariana Islands 

(CNMI) between 2000 and 2030 along with public forest and nonforest areas. Pie chart reflects the percentage of private forest 

land area in each of the mapped change classes.

Northern Mariana Islands

Projected Housing Density Change 

on Private Forest land (2000 to 2030)

Increase: rural 1 or rural 2 to urban/exurban

Increase: rural 1 to rural 2

No change: rural 1 or rural 2

No change: urban/exurban

Nonforest

Public forest/protected land

11%

8%

58%

23%

11%

8%

58%

23%
31

Case Study

Species Banking: Offsetting Development Impacts 

on Saipan’s Endangered Birds

The Saipan Upland Mitigation Bank (SUMBA), 

established in 1998 and administered by the CNMI 

Division of Fish and Wildlife, is a protected area 

designed to help conserve the habitat of Saipan’s 

endangered nightingale reed-warbler from the pressures 

of housing development. The 1,035-acre mitigation 

bank on the northern portion of Saipan was created in 

cooperation with the U.S. Fish and Wildlife Service and 

is the first mitigation bank in the region (Ecosystem 

Market Network 2010). The protected area will be used 

to offset unavoidable impacts to the warblers associated 

with public and private development projects in the 

surrounding area and will be managed for the protection 

of the birds and other wildlife in perpetuity (Abbott et al. 

2002). 

The SUMBA is similar to other mitigation bank systems 

in the United States, whereby developers whose projects 

would affect certain resources can purchase credits to 

protect similar resources through the establishment, 

restoration, or enhancement of wetlands, streams, or 

other conservation areas (U.S. EPA 2012). The SUMBA 

management plan calls for reducing human disturbance, 

controlling predators, and restoring habitat (Abbott et al. 

2002).

The SUMBA will also serve as protected habitat for 

other threatened and endangered species, including the 

Micronesian megapode (Megapodius laperouse) and the 

Mariana swiftlet (Aerodramus bartschi). Furthermore, 

the mitigation bank provides habitat for endemic species 

protected by the CNMI Division of Fish and Wildlife, 

such as the collared kingfisher (Halcyon chloris), 

Mariana fruit-dove (Ptilinopus roseicapilla), and golden 

white-eye (Cleptornis marchei) (Abbott et al. 2002). 

The United Nations Secretariat of the Pacific Regional 

Environment Programme has identified next steps for 

developing a broader site-based conservation program 

in CNMI, including: (1) increased involvement of 

local communities, nongovernmental organizations, 

land users, and other stakeholders; (2) monitoring 

to understand changes and provide feedback for 

conservation and policy mechanisms; and 

(3) maximizing dissemination and use of data to 

provide insights into reasons for declining populations 

(UN Secretariat Pacific Reg. Environ. Prgm. 2012).

The endangered nightingale reed warbler (Acrocephalus 

hiwae) is being protected by the Saipan Upland Mitigation 

Bank. Photo by Daniel W. Clark.
32

One of the four distinctive forest types foundin El Yunque National Forest, the Sierra Palm forests are dominated by the Sierra palm 

(Prestoea montana). Photo by Jerry Bauer.

Puerto Rico

P

uerto Rico is the top of a submerged mountain crest 

located between the Caribbean Sea and the Atlantic 

Ocean, consisting of the main island of Puerto Rico 

and additional small satellite islands (Vieques, Culebra, 

and Mona). Almost three-fourths of the main island of 

Puerto Rico is mountainous interior; the mountains slope 

down to a coastal plain (Gallucci 1987). The climate is 

mild tropical marine, with little seasonal temperature 

variation (U.S. CIA 2011); many small rivers and high 

central mountains provide abundant water, although the 

south coast is relatively dry.

Puerto Rico’s Forests and Population Trends

Puerto Rico has a land base of about 2.2 million acres, 

about 47 percent (~1,020,400 acres) of which was forest 

cover in 200012 (Kennaway and Helmer 2007) about 

87 percent of Puerto Rico’s forest is privately owned 

(Table 1). In 2000, about 15 percent of the land was 

urban and developed land cover (Kennaway and Helmer 

2007). About 5 percent of the island was protected to 

some degree in 1991-92 (Helmer 2004, Kennaway and 

Helmer 2007); that percentage had increased to about 

8 percent by 2012.13

12 Land cover type in Puerto Rico continues to change very 

rapidly, and both forest cover and percentage of area protected 

have increased since the years referenced (Lugo 2013).

13 Personal communication from A.E. Lugo, 2013, Director, 

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

Institute for Tropical Forestry.

32
33

Puerto Rico’s diverse forests have developed over 

alluvial, sedimentary, volcanic, limestone, and serpentine 

substrates. All forests in Puerto Rico are classified by 

Holdridge (1947) as subtropical13; they support moist 

broadleaf evergreen and seasonal evergreen forests, as 

well as deciduous and semi-deciduous forests, cloud 

forests, forested wetlands, and rainforest (Helmer et al. 

2002, Helmer et al. 2008). Puerto Rico’s forests include 

relatively large examples of most of the major Caribbean 

forest types and constitute a locally and globally 

valuable ecological resource (Brandeis et al. 2003). 

About 750 tree species have been documented in Puerto 

Rico, about 550 of which are native trees.13 Introduced 

species are regenerating naturally in established, 

maturing forests and on recently abandoned agricultural 

land (Brandeis et al. 2003); an example is the African 

tulip tree (Spathodea campanulata), which colonized 

abandoned agriculture and pasture and has become the 

most common tree on the main island. Examples of 

native species include American muskwood (Guarea 

guidonia), cabbagebark tree (Andira inermis), and 

pumpwood (Cecropia schreberiana). Gumbo limbo 

(Bursera simaruba) is found in the subtropical dry forest 

life zone and on the tops of limestone hills in much 

of the moist forest zone, as moisture drains quickly 

from this substrate. Sierra palm (Prestoea montana) is 

found in the lower montane wet and rain forests; and 

mangroves in coastal areas, including large patches of 

white mangrove (Laguncularia racemosa) (Brandeis 

et al. 2003).

Puerto Rico’s human population now totals about 

3.7 million (U.S. Census Bureau 2011a); an average 

half a square mile supports about 443 people and nearly 

1.86 miles of road (U.S. CIA 2011). Population growth 

and urbanization over the past two decades has put 

pressure on Puerto Rican forests, and the landscape has 

been much altered by human activities (Brandeis et al. 

2003). 

Development can be seen on the fringes of El Yunque National Forest, near San Juan, Puerto Rico. Photo by Magaly Figueroa, 

U.S. Forest Service, International Institute of Tropical Forestry.
34

Today’s 47 percent forest cover is a dramatic increase 

from a low of 6 percent in the late 1930s and 1940s, 

when forest clearing for agriculture peaked and the 

economy began to shift toward industry and other 

economic pursuits (Kennaway and Helmer 2007). 

Recently the trend toward forest recovery has slowed, 

however, and changes in forest area vary among forest 

types and substrates (Kennaway and Helmer 2007). 

Furthermore, the notable increase in forest cover in 

Puerto Rico also has been accompanied by urban 

expansion, which is influencing the age, type, and 

distribution of forests on the islands (Helmer et al. 

2008). 

Camping area, Aguirre State Forest, Guayama. Puerto Rico’s forests are a valuable recreational resource for the growing and 

increasingly urbanized population. Photo by Magaly Figueroa, U.S. Forest Service, International Institute of Tropical Forestry.

Puerto Rico’s Smaller Islands

Forests on the two islands of Vieques and Culebra 

differ markedly from those on the main island of 

Puerto Rico. The subtropical dry forest of Culebra is 

more open, with smaller trees than the subtropical 

dry forest on Puerto Rico and Vieques. Forest 

cover is as high as 85 percent on Vieques and 

88 percent on Culebra (Brandeis et al. 2003), but 

recent studies have shown that the area of urban 

and built-up or bulldozed lands on these two islands 

increased by 49 percent during the 1990s (Helmer 

and Ruefenacht 2005).
35

Forest Resource Issues and Priorities

• Forest conversion

Rapid land use changes over the past century have 

included conversion from abandoned agricultural or 

pasture land to developed uses; conversion of forest 

is also occurring at increasing rates (Helmer 2004, 

Helmer and Ruefenacht 2005, Helmer et al. 2008). 

Of the 16,722 acres of land converted to urban or 

surface-mined lands from 1991 to 2000, about 22 

percent was forest (Helmer et al. 2008). Although 

total forest cover has actually more than doubled 

since the 1950s with the shift away from agriculture, 

unprotected forest areas near or within urban 

centers continue to be vulnerable to development 

(Kennaway and Helmer 2007).

Most (55 to 66 percent) of the forest that has been 

cleared for land development has been young 

secondary forest (Helmer et al. 2008). About 

13 percent of stands cleared for development was 

mature secondary forest—including old forest on 

karst substrate14 (Brandeis et al. 2003, Kennaway 

and Helmer 2007). 

• Forest recovery on karst topography

About 27 percent of Puerto Rico consists of karst 

geology (Lugo et al. 2007), including sinkholes, 

caves, cliffs, alluvial terraces, long and narrow 

valleys, and limestone hills (Rivera and Aide 

1998). Forest recovery has been underway for at 

least 50 years on abandoned farms in the karst area 

(Kennaway and Helmer 2007, Rivera and Aide 

1998), but the rate of urbanization in the karst is also 

increasing (Lugo et al. 2007); forest recovery on 

karst now is threatened by road construction, fires, 

and commercial and housing development (Rivera 

and Aide 1998). 

14 Repeated fires and grazing also may be contributing to 

the maintenance of younger ages of subtropical dry forest 

(Brandeis et al. 2003).

Karst forest. Photo by Magaly Figueroa, U.S. Forest Service, 

International Institute of Tropical Forestry.

Conversion of Puerto Rico’s forests is occurring at increasing rates. Photos by Magaly Figueroa, U.S. Forest Service, International 

Institute of Tropical Forestry (left) and TexPhoto, istockphoto.com (right).
36

Development Projections

About 24 percent (~ 215,000 acres) of Puerto Rico’s 

private forest land is projected to experience a 

substantial increase in housing density from 2000 to 

2030, such that the category will shift from very rural 

(rural I) to less rural (rural II) or to urban-exurban 

(Fig. 5). Forests expected to undergo this change are 

located across interior areas of Puerto Rico, including 

forests across much of the western half of the main 

island, as well as forests located in the interior southeast. 

Much of the forest remaining around the Maricao State 

Forest is projected to experience a substantial increase 

in housing density, as is land adjacent to several other 

State forests and pockets of private rural forest located 

adjacent to the El Yunque National Forest. 

Figure 5.—Maps show projected housing density change on private forest land in Puerto Rico between 2000 and 2030 along 

with public forest and nonforest areas. Pie chart reflects the percentage of private forest land area in each of the mapped change 

classes.

Puerto Rico

Projected Housing Density Change 

on Private Forest land (2000 to 2030)

Increase: rural 1 or rural 2 to urban/exurban

Increase: rural 1 to rural 2

No change: rural 1 or rural 2

No change: urban/exurban

Nonforest

Public forest

22%

2%

23%

53%

22%

2%

23%

53%
37

Case Study

Collaboration for Conservation: 

The Humacao Joint Priority Landscape 

In the southeastern corner of Puerto Rico, a collaborative 

effort known as the Humacao Joint Priority Landscape is 

bringing area communities together to help prevent the 

loss of forests threatened by urban sprawl. 

Endorsed by the Natural Resource Conservation 

Service, the Puerto Rico Department of Natural and 

Environmental Resources (DNER), the U.S. Fish and 

Wildlife Service, and the U.S. Forest Service—and 

further supported by landowner organizations and other 

groups—the Humacao project seeks to protect numerous 

forest benefits, including:

• Habitat for endemic species such as the Puerto 

Rican parrot (Amazona vittata), Puerto Rican boa 

(Epicrates inornatus), and Puerto Rican rock frog 

(Eleutherodactylus cooki)

• Watershed conservation, restoration, and 

improvement of forest health on properties within 

the several important watersheds in eastern Puerto 

Rico 

• Conservation of forest cover within the buffer and 

protection boundaries of the El Yunque National 

Forest, Puerto Rico State Forests, Natural Refuges, 

and other important ecosystems

• Conservation practices to reduce soil erosion and 

improve water quality

The project uses tree planting, forest improvement 

practices, and education to promote forest conservation, 

habitat restoration, reduction of pest and disease 

occurrence, improvement of soil condition, carbon 

sequestration, and improvement of degraded ecosystems.

“Educational efforts include capacity building and 

specialized training opportunities for tree-care 

professionals, community representatives, and the 

Puerto Rico DNER personnel,” said Magaly Figueroa, 

natural resource specialist for the International Institute 

of Tropical Forestry (IITF). She noted that joint priority 

landscapes provide further opportunity to leverage 

State, Federal, and private partner resources on behalf of 

important private landscapes. 

Joint Priority Landscapes for Puerto Rico were identified 

in the Puerto Rico Assessment and Strategies (Puerto 

Rico DNER 2011). The Humacao project subsequently 

was launched by the Forest Stewardship and Urban 

Community Forestry programs of the U.S. Forest 

Service in Puerto Rico. These programs focus on 

providing technical and management planning assistance 

to private landowners within the Humacao region, and 

on educating children in kindergarten through grade 12 

about the importance of forest stewardship. 

Additional sources: U.S. Forest Service 2012; personal 

communication from M. Figueroa, 2012, natural 

resources specialist, U.S. Department of Agriculture, 

Forest Service, International Institute of Tropical Forestry

Forests near El Yunque National Forest are among those benefitting from conservation efforts of the Humacao Joint Priority 

Landscape. Photo by Tana Wood.
38

St. John, U.S. Virgin Islands. Photo by Kee Tron, istockphoto.com.

U.S. Virgin Islands

The U.S. Virgin Islands (USVI), part of the Caribbean’s 

Lesser Antilles, encompass dozens of islands and cays, 

the largest of which are St. Croix, St. Thomas, and 

St. John. The climate is mostly subtropical, with a hot 

and humid rainy season from May to November and a 

dry season more tempered by trade winds; the islands 

are vulnerable to substantial damage from storms 

(Kennaway et al. 2008). USVI geological substrates 

include alluvial, sedimentary, volcanic, and limestone 

layers (Chakroff 2010).

U.S. Virgin Islands Forests and Population Trends

Forest covers about 53,000 acres or about 63 percent 

of USVI’s total land area (~ 84,000 acres) (Table 1). 

St. John has the highest percentage of forest land 

(92 percent), followed by St. Thomas (70 percent), 

and St. Croix (50 percent) (Brandeis and Oswalt 2007, 

Kenneway et al. 2008). With the exception of the Virgin 

Islands National Park, which encompasses and protects 

some 65 percent of land on St. John, most USVI forests 

are privately owned (Kennaway et al. 2008) (Table 1).

The forests of the three islands are somewhat different 

but the two major forest types are subtropical15 moist 

forest (~ 22,000 acres) and subtropical dry forest 

(~ 31,000 acres) (Brandeis and Oswalt 2007, Chakroff 

2010), mostly secondary growth (Kennaway et al. 2008). 

As elsewhere in the Caribbean, the interaction between 

trade winds and steep topographical gradients can lead to 

changes in forest types over short distances (Kennaway 

et al. 2008).

15 As defined by the Holdridge system of life zone 

classification (see footnote 13) (Lugo 2013).

38
39

The subtropical moist forests include evergreen forest 

found at higher elevations with substantial rainfall and 

clouds and in riparian corridors and valleys at lower 

elevations with sufficient fresh water. These forests 

support numerous shrubs, vines, epiphytes, and more 

than 100 tree species, including early successional black 

olive (Bucida buceras), sandbox tree (Hura crepitans), 

and silk-cottonwood (Ceiba pentandra) (Brandeis and 

Oswalt 2007, Chakroff 2010). 

Subtropical dry forests include lowland semi-deciduous 

and drought-deciduous forests that vary widely in 

structure and are heavily influenced by rainfall, slope 

and aspect, prevailing winds, and sea spray (Chakroff 

2010). USVI dry forest species include gumbo limbo 

tree (Bursera simaruba), Jamaican caper (Capparis 

cynophallophora), orange manjack (Cordia rickseckeri), 

lignum vitae (Guaiacum officinale), and frangipani 

(Plumeria alba). Other USVI forest types include moist 

tropical forest and coastal mangrove forests.

U.S. Virgin Island forests are located in one of the 

world’s “biodiversity hotspots.” They are highly valued 

for their scenic beauty, as well as for their contribution 

to cultural and ecological services including rainwater 

infiltration, soil stabilization, and forest-related arts and 

crafts. They also provide vital wildlife habitats, such as 

critical wintering grounds for migrating neotropical birds 

and habitats for several species of bats, USVI’s only 

native mammals (Chakroff 2010). 

Intact Island Forests 

Provide Biodiversity “Hotspots” 

The Caribbean Basin is a global biodiversity hotspot—

a biologically rich area whose plant or animal habitats 

have been sharply reduced. Caribbean islands and their 

forests provide invaluable habitats for resident birds and 

vital wintering grounds for many neotropical migrant 

songbirds, including declining species of warblers 

such as the Cape May warbler (Dendroica tigrina), 

blackthroated blue warbler (D. caerulescens), and prairie 

warbler (D. discolor). The U.S. Virgin Islands is home 

to some 315 threatened and endangered terrestrial 

species. 

Cape May warblers are neotropical birds that rely on low- —Source: Brandeis and Oswalt 2007

elevation Caribbean forests for winter habitat. Photo by 

Gharrold, istockphoto.com. 

Shade-tolerant epiphytes, shrubs, and vines develop 

beneath the mostly closed canopy. Examples of 

indicator tree species of the dry forest are gumbo limbo 

tree (Bursera simaruba), Jamaican caper (Capparis 

cynophallophora), orange manjack (Cordia rickseckeri), 

lignum vitae (Guaiacum officinale), and frangipani 

(Plumeria alba) (Chakroff 2010).

About 109,000 residents live year-round in the U.S. 

Virgin Islands (U.S. Census Bureau 2011e), with a recent 

population growth rate of 8 percent (Chakroff 2010). The 

islands are host to more than 2 million visitors annually 

(Brandeis and Oswalt 2007, Chakroff 2010). Ninety-five 

percent of Virgin Islanders live in an urban environment; 

urban and developed land area on the three major islands 

covered about 14,000 acres in 2000, and urban growth 

has increased further over the past decade at the expense 

of forested areas (Kennaway et al. 2008).

Forest structure, ecosystem function, and species 

composition of USVI forests have been strongly 

influenced by forest clearing (Kennaway et al. 2008). 

Only fragments of USVI’s original old-growth forests 

remain because of past aggressive land clearing and 

agricultural activities (Brandeis and Oswalt 2007, 

Chakroff 2010, Kennaway et al. 2008). Although the 

islands may have been 90 percent forested prior to 

European colonization (Brandeis and Oswalt 2007), by 

1800 only about 5 percent or less of the forest cover 

remained, having been cleared primarily for sugar cane 
40

and cotton agriculture (USVI Dept. of Agric. 2010). 

With abandonment of agriculture from the 1800s to 

the early 20th century, forests gradually recovered 

(Brandeis and Oswalt 2007, Kennaway et al. 2008). 

However, in the past decade, young secondary forests 

have been increasingly cleared for expansion of urban 

areas, dispersed housing developments, and expansion 

of resorts, golf courses, and other tourism-related 

infrastructure (Brandeis and Oswalt 2007). Between 

1994 and 2004, 11 percent of St. Croix’s subtropical dry 

forest was lost, while St. Thomas lost 13 percent of its 

subtropical dry forest (Brandeis and Oswalt 2007).

Forest Resource Issues and Priorities

• Forest loss to development

The decrease of forest cover from 1994 to 2004 

illustrates that past gains in USVI’s forest cover are 

being lost (Brandeis and Oswalt 2007). Unprotected 

low-elevation forests face the greatest danger 

of deforestation due to development pressure 

(Kennaway et al. 2008). Contiguous forest (large 

patches of forest that are close although not always 

adjacent to other forest patches) and transitional 

St. Thomas, U.S. Virgin Islands. Photo by Keith Binns, istockphoto.com.

forest (areas that are changing to forest from 

agricultural or other uses) are most threatened by 

conversion to buildings and urban areas (Chakroff 

2010). Even on St. John, where 65 percent of 

the island is a national park that protects the 

island’s interior high-elevation semi-evergreen 

and deciduous forests, unprotected low-elevation 

dry forests are endangered and highly susceptible 

to development pressures. On St. Thomas, where 

such protections are not in place, development 

pressure is seen island-wide (Kennaway et al. 2008). 

With the loss or degradation of forests comes the 

loss of ecosystem services such as clean water; 

consequently, drinking water quality is among 

the foremost concerns in the U.S. Virgin Islands 

(Chakroff 2010).

• Urban forest sustainability

Forty-eight percent of the forests of St. Croix and 

60 percent of St. Thomas forests are classified as 

urban or community forest (Chakroff 2010). These 

forests contribute innumerable services to the people 

of the Virgin Islands, including health benefits, 
41

shade and cooling, clean air, cultural and economic 

values, and recreation opportunities (Chakroff 

2010). Urban forests are being fragmented and 

impaired, especially near roads, in part because of 

their accessibility and in part from lack of adequate 

oversight, management, and maintenance (Chakroff 

2010, Kenneway et al. 2008). In addition, urban 

and rural trees are subject to tropical storms and 

hurricanes, which not only damage the trees but 

also create hazards to vehicles, homes, and people 

(Chakroff 2010).

• Degradation of coastal forest ecosystems

Coastal areas with desirable views and ocean access 

are a prime target for development activities; such 

activities can be particularly damaging to coastal 

forests and the coral reefs that rely on forest’s 

to reduce and filter sediment from runoff and to 

stabilize shorelines (Chakroff 2010). Upland and 

coastal development is increasing the amount and 

magnitude of runoff from buildings and roads, thus 

threatening USVI coral reefs (Brandeis and Oswalt 

2007, Chakroff 2010, Gray et al. 2008). Degraded 

Urban trees and forests are a vital part of USVI’s natural landscape. Photo by Julie Hewitt, istockphoto.com.

and diminished coral reefs affect not only wildlife 

and fish but also the island’s tourism-based economy 

(Chakroff 2010).

Organic sediment is particularly harmful to coral reefs, such 

as those found in Trunk Bay, pictured here. In one 2007 rainy 

season the rate of organic deposits was 28 times higher for a 

coral reef below a developed USVI watershed than it was for 

a reef below an undeveloped watershed (Gray et al. 2008). 

Photo by Daniel W. Clark.
42

Development Projections

About 12 percent (~5,400 acres) of USVI’s private 

forest land is projected to undergo a substantial increase 

in housing density from 2000 to 2030, such that the 

category will shift from very rural (rural I) to less rural 

(rural II) or to urban-exurban (Fig. 6). Substantial 

housing increases are projected to occur in localized 

areas across the Virgin Islands, most notably in much 

of the remaining rural private forest across inland areas 

of northern St. Thomas. Increases are also expected in 

smaller patches of St. Thomas’ coastal forests, including 

those located on Neltjeberg Bay on the northeastern area 

of the island, as well as forests along Bovani Bay and the 

northeastern tip of Western Island. Projected change for 

St. John is minimal.

Figure 6.—Maps show projected housing density change on private forest land in U.S. Virgin Islands between 2000 and 2030 

along with public forest and nonforest areas. Pie chart reflects the percentage of private forest land area in each of the mapped 

change classes.

U.S. Virgin Islands

Projected Housing Density Change 

on Private Forest land (2000 to 2030)

Increase: rural 1 or rural 2 to urban/exurban

Increase: rural 1 to rural 2

No change: rural 1 or rural 2

No change: urban/exurban

Nonforest

Public forest

No projection data available

9%

3%

34% 53%

1.5%1.5% 9%

3%

53% 34%
43

Case Study

Caribbean Landscape Conservation Cooperative 

(CLCC): Science and Technology for Conservation 

Planning and Action 

The U.S. Forest Service’s International Institute for 

Tropical Forestry (IITF) has worked with other Federal 

and local agencies to establish the Caribbean Landscape 

Conservation Cooperative (CLCC), bringing the U.S. 

Virgin Islands and Puerto Rico into a national network 

of 22 landscape conservation cooperatives. The CLCC 

mission is “providing science and technology for 

conservation planning and action—addressing the need 

to restore and sustain natural resources in Caribbean land 

and seascapes.”

Landscape conservation cooperatives involve applied 

conservation science partnerships among State and 

Federal agencies, regional organizations, tribes, 

nongovernmental organizations, universities, and other 

entities within a geographic area. They are designed 

to provide science to inform resource management 

decisions in an integrated fashion across landscapes—

at a broader scale than any individual partner’s 

responsibility. Landscape conservation cooperatives 

consider landscape-scale stressors including climate 

change, habitat fragmentation, urban sprawl, invasive 

species, and water availability in order to assess the 

conservation status of species and habitats and provide a 

vision for sustainable landscapes under future scenarios. 

The CLCC emphasizes the connectivity of USVI 

and Puerto Rico with the greater Caribbean and the 

continental regions through shared species, habitats, and 

conservation opportunities and goals. The CLCC aims 

to provide a regional context for conservation planning 

and management at different scales—from decisions on 

site management to understanding the implications of 

management actions regionally, nationally, and globally. 

—Source: U.S. Forest Service 2012

The International Institute of Tropical Forestry (IITF). Photo by Maya Quinones, U.S. Forest Service. 

The map shows the extent of the Caribbean Landscape Conservation Cooperative in 2011. Colors 

represent developed land (black), forested land (green), shrubland (brown), and grassland (light tan). 

Source: U.S. Forest Service 2012. 
44

Summary and Conclusions

H

awaii, Puerto Rico, and other Pacific and Caribbean 

islands encompass diverse and invaluable tropical 

and subtropical forest resources that are confronted 

by housing pressures similar to those faced by mainland 

forests. Unlike the mainland, however, islands face 

additional challenges due to their small size, relative 

isolation, and unique plant and animal life. Island forests 

are highly susceptible to storms and climate change, and 

exceptionally vulnerable to the introduction of nonnative 

species (U.S. Forest Service 2007). Many have high 

demands for recreation, tourism, and agroforestry 

or forest product businesses but some have limited 

resources for forest management or development of 

sustainable forest products (U.S. Forest Service 2007). 

Private forests across these islands have been affected 

by past and present land use choices and are increasingly 

vulnerable to impacts from future development.

In localized areas of every island complex covered by 

this report, from 3 to 25 percent of private forest land 

could experience a substantial increase in housing 

density between 2000 and 2030. Such projections—

based on long-term growth trends and patterns, road 

densities, and locations of urban areas—assume that 

removal, fragmentation, or degradation of private forests 

on the islands is likely to continue despite the fact that, 

with the exception of Hawaii, human populations on 

the islands have declined somewhat in the past decade 

(Census Bureau 2011a-e).

As seen in the case studies sampled here, much 

is being done throughout America’s Pacific and 

Caribbean islands to prevent, reduce, or reverse the 

impacts of development on island forests. Creative and 

comprehensive approaches have included biological 

control of invasive species in Hawaii, restoration of 

native ecosystems through nurseries and training in 

American Samoa, and technical assistance for private 

landowners in Puerto Rico. Other positive steps include 

successful education and outreach in Guam, mitigation 

banking that protects endangered and endemic species 

in the Commonwealth of the Northern Mariana Islands, 

and a landscape-scale conservation collaborative in the 

U.S. Virgin Islands and Puerto Rico. The U.S. Forest 

Service’s Forest Stewardship, Forest Legacy, and Urban 

Forestry programs also have helped focus substantial 

effort on preservation and restoration of native forests on 

the islands. 

But the stakes are high and the work is nowhere near 

complete. Although in some places such as Puerto 

Rico, forest cover has increased substantially in recent 

decades, in other places such as Guam, accelerated loss 

of forest is expected to accompany an abrupt rise in 

population and development in the near future. Forests 

throughout the islands remain exposed to threats from 

invasive species of plants and animals, in part due to 

housing development. 

As in other Forests on the Edge reports, the development 

projections reported here serve not to pinpoint specific 

locations where housing development will occur but 

rather to suggest areas where development and related 

impacts can be expected at a broader scale. Some places 

identified here might have constraints or conditions that 

could preclude actual development—such as extremely 

steep slopes, or economic or social constraints—that our 

models were not able to consider fully.

It is critical that resource managers, developers, 

community leaders, and landowners consider the unique 

and sensitive ecologies of island forests when planning 

for future development. This is especially important 

in light of the added stressors that climate change will 

bring. Careful planning will help sustain and protect 

native species, water, and forest ecosystems—along with 

the people and cultures that depend on them.

The endangered halapepe (Pleomele hawaiiensis) in flower, 

Puuwaawaa, Hawaii Island, Hawaii. Photo by J.B. Friday.
45

Acknowledgments

We are grateful for the assistance of many 

individuals who helped guide, clarify, and 

improve the accuracy of this report, which covers 

areas that are not well-represented in the scientific 

literature in terms of current and consistent data on 

forests and development. We are particularly grateful to 

Lisa G. Mahal, University of Nevada/Las Vegas; Ronald 

E. McRoberts and Mark D. Nelson, U.S. Forest Service, 

Northern Research Station, for data and analysis in early 

stages; and Marge Victor, Oregon State University, for 

early drafts and research. We updated, expanded, and 

edited their prior contributions to produce this report. 

Extensive contributions and detailed technical reviews 

were provided by Susan Cordell, U.S. Forest Service, 

Institute of Pacific Islands Forestry; James B. Friday, 

University of Hawaii at Manoa, Komohana Research 

and Extension Center; and Eileen Helmer and Ariel 

Lugo, U.S. Forest Service, International Institute of 

Tropical Forestry. As with all Forests on the Edge 

reports, we continue to be grateful to David Theobald, 

senior scientist with Conservation Science Partners, 

Fort Collins, CO, for his insightful analyses and data on 

population and housing density.

The following specialists reviewed and provided 

instrumental content or clarification: Russell Benford, 

Commonwealth of the Northern Mariana Islands, 

Division of Fish and Wildlife; Ron Cannarella, Hawaii 

Department of Land and Natural Resources, Division 

of Forestry and Wildlife Planning and Information 

Services; Joe Donnegan, Forest Service, Forest 

Inventory and Analysis program; Lisa Fischer and 

Zhanfeng Liu, Forest Service, Pacific Southwest 

Region, Remote Sensing Lab; Magaly Figueroa, Forest 

Service, International Institute for Tropical Forestry, 

State and Private Forestry; Kathleen Friday, Forest 

Service, Pacific Southwest Region, State and Private 

Forestry; Diane Haase, Forest Service, Pacific Northwest 

Region, Cooperative Programs; John (Bart) Lawrence, 

USDA Natural Resources Conservation Service, Pacific 

Islands Area, Guam; Sheri Mann, Hawaii Department 

of Land and Natural Resources, Division of Forestry 

and Wildlife; and Ana Tunabuna-Buli, Land Resources 

Division of the Secretariat of the Pacific Community. 

Carly Wyman and Jennifer Geraci, Forest Service, 

Publishing Arts, helped research and write case studies.

Metrics Table 

When you know: Multiply by: To find:

Acres (ac) 0.405 Hectares (ha)

Feet (ft) 0.305 Meters (m)

Inches (in.) 2.540 Centimeters (cm)

Miles (mi) 1.609 Kilometers (km) 

Square miles (mi2) 2.590 Square kilometers (km2)

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51

Appendix: Methodology Details

Technical Information Regarding Datasets and Analysis

An overview of the analysis process appeared earlier 

in this report in the Methods section. The aim of this 

appendix is to provide sufficient additional detail so 

that interested parties can replicate or critique the 

methodology.

Maps appearing in this report were produced by using 

geographic information system (GIS) software (Esri’s 

ArcMap 10.0), including core functionality as well as 

the spatial analyst extension. Graphs were produced by 

exporting attribute data from geospatial datasets and 

generating summaries using pivot tables in Microsoft 

Excel 2010.

To assess the potential for increased housing 

development to impact private forest land, geospatial 

datasets were constructed that represent: (1) projected 

housing density changes between 2000 and 2030, 

(2) land ownership, and (3) land cover. All datasets were 

converted to raster format at a resolution that matched 

the available land cover data for each island. Additional 

detail for each of the data types is provided below.

Projected Housing Density Changes Between 2000 and 

2030

Using population and housing density data from the 

2000 U.S. Census (U.S. Census Bureau 2001 a-c) as a 

baseline16, projections of housing density increases were 

derived from predicted population changes. A spatially 

explicit model was used to predict the full urban-to rural 

spectrum of housing densities (Theobald 2005). The 

same projection approach was used in previous FOTE 

reports, and additional discussion and description can 

be found in those sources (for example, refer to the 

appendix in the Private Forests/Public Benefits report 

[Stein et al. 2009]). 

The projected housing density dataset contains elements 

of land use in addition to housing density categories 

(Table A-1). The land use categories are necessary to 

identify areas that are likely not developable. Categories 

in the projected housing density layer were aggregated 

into the general density categories used in this report, 

namely rural 1, rural 2, exurban, and urban (Table A-1).

Land Ownership

Ownership data for the islands were gathered from 

publicly available data sources and were compiled to 

create a geospatial data layer depicting ownership in five 

categories: private unprotected, private protected, public, 

tribal, and private unprotected (undevelopable). 

Land Cover

As described in the Methods section, sources of land 

cover were different for each island (Table A-2). 

The selection of land cover data source was based 

on a combination of dataset completeness and local 

expert opinion on the suitability of each dataset for 

distinguishing forest from nonforest. Land cover 

or vegetation categories for each data source were 

collapsed to a binary forest/nonforest designation 

(Tables A-3, A-4).

Once the three geospatial datasets were created for each 

island and converted to a common raster format and 

resolution, they were combined using a GIS operation 

(ArcMap spatial analyst combine command). The result 

of this operation was the attribution of each raster pixel 

on the island with the information provided in the three 

datasets. 

A simple set of decisions was then applied in order to 

assign each pixel to a final map category (Fig. A-1). We 

opted to use a simple, straightforward mapping process 

to provide maximum transparency of the methodology. 

For American Samoa’s Tutuila island only, we added 

an elevation threshold to the housing density model 

such that development was precluded from areas above 

328 feet above sea level, based on Digital Elevation 

Model data (Lim et al. 2010). This modification was in 

response to local experts who indicated that the northern 

coast of Tutuila is exceptionally steep and unlikely to be 

developed because of the rugged terrain.

16 2010 housing data for the trust territories were not available 

at the time of Theobald’s (2005) housing density analysis.
52

Table A-1.—Categories in a projected housing density geospatial datasets for subtropical and tropical 

islandsa, and the corresponding aggregated mapped categories

Housing Density Category Land use classes included

 Rural 1

Barren (and <8 units/mi2

)

Forestry (and <8 units/mi2)

Grazing (and <8 units/mi2)

Intensive agriculture (cropland and <8 units/mi2)

Residential - (very low-density, 8-16 units/mi2

)

 Rural 2

Residential - (low-density, 16-32 units/mi2)

Residential - (low-moderate density, 32-64 units/mi2)

 Exurban/urban

Residential - (moderate-density, 64-376 units/mi2

)

Residential - (moderate-high, 376-1067 units/mi2)

Residential - (high, 1067-6400 units/mi2)

Residential - (very high, >6400 units/mi2)

 Not developable

Commercial/industrial

Transportation

Urban parks/open space

Water

Built-up public land

Wetlands/riparian

Protected lands

a Hawaii, Guam, American Samoa, Commonwealth of the Northern Mariana Islands, Puerto Rico, and U.S. Virgin Islands.

Island/complex Dataset description Resolution Source

Hawaii LANDFIRE Existing Vegetation Type 30 m USDI and USDA (2013)

Guam Satellite imagery classification by the U.S. 

Forest Service

15 m Liu and Fischer (2007)

American Samoa Satellite imagery classification by the U.S. 

Forest Service

15 m Liu and Fischer (2006b)

Commonwealth of the 

Northern Mariana Islands

Satellite imagery classification by the U.S. 

Forest Service

15 m Liu and Fischer (2006a)

Puerto Rico—main island, 

Vieques, and Culebra

National Land Cover Data (NLCD) database 15 m Homer et al. (2007), based on 

Kennaway and Helmer (2007)

Puerto Rico—Mona Island Landsat, Ikonos imagery 15 m Martinuzzi et al. (2008)

U.S. Virgin Islands Satellite imagery and coarse resolution Lidar 15 m Kennaway et al. (2008)

Table A-2.—Sources of forest land cover definitions for the islands
53

Barren/sandy beach/bare 

rocks

Cropland

Other shrub and grass

Savanna complex

Strand

Urban built-up

Urban vegetation

Water

Wetland

Agroforest

Agroforest - coconut

Casuarina thicket

Leucaena leucocephala

(tangantangan)

Mixed introduced forest

Native limestone forest

Hawaiian introduced 

wetland vegetation – shrub

Hawaii wet cliff and ridge 

crest shrubland

Hawaii lowland dry 

shrubland

Hawaii lowland mesic 

shrubland

Hawaii montane – 

subalpine dry shrubland

Hawaii alpine dwarf 

shrubland

Hawaii dry cliff

Hawaii dry coastal strand

Hawaii wet – mesic coastal 

strand

Hawaii subalpine mesic 

shrubland

Hawaiian introduced 

deciduous shrubland

Hawaiian introduced 

evergreen shrubland

Introduced coastal wetland 

vegetation – shrub

Open water

Barren

Developed – open space

Developed – low intensity

Developed – medium 

intensity

Developed – high intensity

No data

Hawaii bog

Hawaii lowland dry 

grassland

Hawaii lowland mesic 

grassland

Hawaii montane – 

subalpine dry grassland

Hawaii montane – 

subalpine mesic grassland

Hawaiian introduced 

perennial grassland

Introduced coastal wetland 

vegetation – herbaceous

Agriculture – cultivated 

crops and irrigated 

agriculture

Hawaiian introduced 

wetland vegetation 

– herbaceous

Hawaiian introduced 

wetland vegetation - tree

Hawaii lowland rainforest

Hawaii montane cloud 

forest

Hawaii montane rainforest

Hawaii lowland dry forest

Hawaii lowland mesic forest

Hawaii montane-subalpine 

dry forest and woodland

Hawaii montane-subalpine 

mesic forest

Hawaiian introduced dry 

forest

Hawaiian introduced wetmesic forest

Introduced coastal wetland 

vegetation - tree

Hawaiian managed tree 

plantation

Littoral strand

Marshes

Summit scrub

Montane scrub

Agriculture

Urban cultivated

Secondary scrub

Sandy beach/bare rocks

Quarry and landfill

Urban built-up

Water

Freshwater swamps

Mangroves

Rainforest

Rhus secondary forest

Table A-3.—Categories in land cover or vegetation geospatial datasets for U.S.-affiliated subtropical and 

tropical islands in the Pacific Ocean and the corresponding forest/nonforest categories

American Samoa

Forest Nonforest

CNMI

Forest Nonforest

Hawaii

Forest Nonforest

Agriculture field

Badland

Barren

Coconut plantation

Marsh land

Other shrub/grass

Sandy beach/bare rocks

Savanna complex

Strand vegetation

Urban built-up

Urban cultivated

Water

Wetland

Acacia plantation

Casuarina thicket

Leucaena stand

Limestone forest

Mangrove swamp

Palma brava grove

Ravine forest

Scrub forest

Guam

Forest Nonforest
54

Table A-4.—Categories in land cover or vegetation geospatial datasets for U.S.-affiliated subtropical and 

tropical islands in the Caribbean and the corresponding forest/nonforest categories

Background/water

High-medium density urban

Low-medium density urban

Herbaceous agriculture 

– cultivated lands

Pasture, hay, or inactive 

agriculture (e.g., abandoned 

sugar cane)

Pasture, hay, or other 

grassy areas (e.g., soccer 

fields)

Emergent wetlands 

including seasonally flooded 

pasture

Salt or mud flats

Tidally flooded evergreen 

dwarf-shrubland and forb 

vegetation

Quarries

Coastal sand and rock

Bare soil (including 

bulldozed land)

Water – permanent

Active sun coffee and mixed 

woody agriculture

Drought deciduous open 

woodland

Drought deciduous dense 

woodland

Deciduous, evergreen 

coastal, and mixed forest or 

shrubland with succulents

Semi-deciduous and 

drought deciduous forest on 

alluvium and non-carbonate 

substrates

Semi-deciduous and drought 

deciduous forest on karst 

(includes semi-evergreen 

forest)

Drought deciduous, semideciduous, and seasonal 

evergreen forest on 

serpentine

Seasonal evergreen and 

semi-deciduous forest on 

karst

Seasonal evergreen and 

evergreen forest

Seasonal evergreen forest 

with coconut palm

Evergreen and seasonal 

evergreen forest on karst

Evergreen forest on 

serpentine

Elfin, sierra palm, 

transitional, and tall cloud 

forest

Mangroves

Seasonally flooded 

savannahs and woodlands

Pterocarpus swamp

U.S. Virgin Islands

Forest Nonforest

Open water

Developed – open space

Developed – low intensity

Developed – medium 

intensity

Developed – high intensity

Shrub/scrub

Grassland/herbaceous

Pasture/hay

Cultivated crops

Emergent herbaceous 

wetlands

Evergreen forest

Woody wetlands

Puerto Rico

Forest Nonforest

Woodland and shrubland

Nonforest vegetation

Barren

Urban

Forest

Puerto Rico, Mona Island

Forest Nonforest
55

Figure A-1.—Logic applied to three geospatial datasets to determine the impact of projected housing density changes on private 

forest land. Colors (rectangles) correspond to maps found earlier in the report. For American Samoa’s Tutuila Island only, we added 

an elevation threshold to the housing density model such that development was precluded from areas 328 feet or more above 

sea level.

Forest/

nonforest

Private/

public

Housing

density

Forest?

Nonforest

(white)

No Private? Yes

Public forest

(dark green)

No

Geospatial data layers

Urban/

Exurban

att1?

Rural at

t1 and t2?

R1 to R2?

Rural to

Urban/

Exurban?

Not

Developable

No change

(gray)

Increase

(red)

Increase

(orange)

No change

(light Green)

No change

(gray)

No

No

No

Private forest land

Yes

Yes

Yes

Yes

Yes Yes

No

Emerald tree skink, also called the green tree skink, (Lamprolepis smaragdina). 

Photo by Daniel W. Clark.
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 contract 

USDA’s TARGET Center at 202-720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 

1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call 800-795-3272 (voice) or 202-720-6382 (TDD). USDA is an equal opportunity 

provider and employer.

Forests on the Edge 

Forests on the Edge is a project of the U.S. Forest 

Service, State and Private Forestry, Cooperative 

Forestry staff, in conjunction with the Forest Service’s 

Research and Development and National Forest System 

deputy areas, universities, and other partners. The 

project aims to increase public understanding of the 

contributions of and pressures on America’s forests, 

and to create new tools for strategic planning. The first 

report identified private forested watersheds in the 

conterminous United States most likely to experience 

increased housing density. Subsequent reports have 

provided more in-depth discussion and data on: 

development pressures on America’s national forests 

and grasslands, impacts of increased housing density 

and other pressures on private forest benefits, threats 

to at-risk species, sustaining America’s urban trees and 

forests, and understanding and preparing for wildfire in 

the wildland-urban interface, among others. Forests on 

the Edge publications can be viewed or downloaded 

at the Forest Service Open Space Web site, 

http://www.fs.fed.us/openspace/fote.

Future Forests on the Edge reports in preparation 

feature the role of forests in protecting surface drinking 

water and potential impacts of future development; 

impacts of increased housing density on forest woody 

biomass; and impacts of climate change and rising sea 

levels on island forests. 

For further information on Forests on the Edge, contact: 

Coordinator, Open Space Initiative 

U.S. Forest Service, Cooperative Forestry staff

1400 Independence Avenue, SW, Mailstop 1123

Washington, DC 20250-1123

http://www.fs.fed.us/openspace/fote/ 

Photos on front cover, from top then left to right: Elysiumm/istockphoto.com; J.B. Friday; EhPoint/istockphoto.com; 

KeithBinns/istockphoto.com. Back cover: Skibreck, istockphoto.com.