80

he Caribbean and Pacific islands that are affiliated with the US provide a

unique setting for consideration of climate variability and change. Islands contain diverse and productive ecosystems,and include many specialized and unique

species. After centuries of depending on subsistence agriculture and fishing,island

economies are now based heavily on tourism,tuna processing and transshipment,

and agricultural production for export (including sugar cane,bananas,pineapple,

spices,and citrus fruits),making them highly responsive to external economic

forces. The stability of these economies is also dependent on the health of the

unique natural resources,all of which are sensitive to climate.

Many islands are facing the stresses of rapid human population growth,increasing

vulnerability to natural disasters,and degradation of natural resources.Droughts and

floods are among the climate extremes of most concern as they affect the amount

and quality of water supplies in island communities and thus can have significant

health consequences.Due to their small size and isolation,many islands face chronic water shortages and problems with waste disposal. Some are facing a species

extinction crisis; for example,the Hawaiian Islands have the highest extinction rate

of any state in the nation. For most island communities,infrastructure and economic activities are located near the coast,making them highly vulnerable to storm

events and sea-level fluctuations.

Observed Climate Trends

n the Pacific,tropical storms and typhoons are common between May and

December, but can occur in any month. In the Caribbean,the hurricane season

spans the months from June to November. The El Niño Southern Oscillation

(ENSO) cycle affects sea level,rainfall,and cyclone activity (hurricanes or typhoons,

depending on the region). In the Caribbean, Atlantic hurricanes are suppressed

during El Niño,while they increase during La Niña. In the Pacific,during El Niño

events,Hawaii,Micronesia,and the islands of the southwest tropical Pacific often

receive below normal rainfall. Additionally, areas of above normal precipitation,

along with greater tropical cyclone activity, typically shift eastward towards French

Polynesia. The region of greater tropical cyclone activity includes the central Pacific

(Hawaiian waters),eastern Marshalls and Guam,and northern Marianas.

Over the last century, average annual temperatures in the Caribbean islands have

increased by more than 1oF (0.5oC). Average annual temperatures in the Pacific

Islands have increased by about 0.5oF (0.25oC). Globally,sea level has risen by 4 to

8 inches (10-20 cm) in the past 100 years with significant local variation. Relative

The Value of Climate

Forecasts

The 1997-1998 El Niño event offers a vivid

example of how information about potential

consequences can be used to support decision making and benefit society. In 1997,

the Pacific ENSO Applications Center

(based in Hawaii and Guam) provided early

forecasts of El Niño-related droughts in

Hawaii, Micronesia, and the tropical southwest Pacific. The Applications Center subsequently pursued an aggressive program

of government briefings, public education,

and outreach. As a result, many Pacific

Island governments established "drought

task forces" and developed mitigation

plans. In addition to addressing governmental actions, these drought task forces

helped inform the public about strategies to

conserve water, prevent outbreaks of diseases associated with droughts, and reduce

the risk of wildfires that often increase during droughts.

These task forces employed radio and television announcements, information hotlines,

brochures, and presentations on El Niño

and drought in local schools. In response

to the public information campaign, water

I

ISLANDS IN THE CARIBBEAN

AND THE PACIFIC

T

Hawaiian Islands

KEY ISSUES

• Freshwater Resources

• Public Health and Safety

• Ecosystems and

Biodiversity

• Sea-level Variability 

The scope of this section includes the USaffiliated islands of the Caribbean and

Pacific. In the Caribbean, this includes

Puerto Rico and the US Virgin Islands. In

the Pacific, it includes the Hawaiian

Islands, American Samoa, the

Commonwealth of the Northern Mariana

Islands, Guam, the Federated States of

Micronesia, the Republic of the Marshall

Islands, and the Republic of Palau.
81

Some models suggest more

persistent El Niño-like conditions across the Pacific. This

would lead to a reduction of

fresh water resources.

management agencies implemented water

conservation plans and repaired their systems; residents repaired their water catchment systems; and local vendors supplied

new catchment systems and new water

storage tanks.

Even with these precautionary measures,

the 1997-1998 El Niño produced such

extensive drought conditions that water

rationing became necessary, limited hours

of water use were imposed on most islands,

and eventually water augmentation was

required on several Pacific islands.

sea level,which also takes into account natural and human-caused changes in

the land elevation such as tectonic uplifting and land subsidence (sinking),is

also showing an upward trend (3.9 inches, about 10 cm,per 100 years) at sites

monitored in the Caribbean and Gulf of Mexico. Although absolute sea level is

also rising in the Pacific,trends vary greatly from island to island due to the fact

that some islands are rising;ENSO and other short-term variations further complicate the picture. Low-lying islands that are not rising are very likely to be at

risk from sea-level rise.

Scenarios of Future Climate 

acific and Caribbean islands will possibly be affected by: changes in patterns of natural climate variability (such as ENSO); changes in the frequency, intensity, and tracks of tropical cyclones;and changes in ocean currents.

These islands are very likely to experience increasing air and ocean temperatures and changes in sea level (including storm surges and sustained rise).

Some recent climate model studies also project that ENSO extremes are likely

to increase with increasing greenhouse gas concentrations. Some models suggest more persistent El Niño-like conditions across the Pacific. This would lead

to a reduction of fresh water resources in areas of the western Pacific,

Micronesia,and the southwest tropical Pacific,and a reduction in Atlantic hurricane frequency.

One hurricane modeling study suggests that peak wind speed will increase by

5-10% by the end of the 21st century along with significant increases in peak

precipitation rates. Apart from the linkage with ENSO, there is significant

uncertainty about how increasing global temperatures will affect hurricane and

typhoon frequency and tracks.

P

Agriculture suffered from the droughts

everywhere except on Guam, where there

was ample water for irrigation.

Still, the consequences could have been

worse. Advance warning through emerging

forecasting capabilities and a focused program of education and outreach clearly

helped mitigate the negative impacts.

These actions prevented death and greatly

reduced suffering to less than occurred during the 1983 El Niño.

Endangered Hawaiian hakalau. Coral reef ecosystem. Mangrove. 

Islands are home to unique

ecosystems and species,

with unsurpassed biodiversity. These resources are

already threatened by invasive non-native plant and

animal species, as well as

urban expansion and various

industrial activities, resulting

in the highest extinction rates

of all regions of the US.

They can also be highly

climate-sensitive.
Freshwater Resources

dequate water supplies are critical for the well-being and economic security of the islands and are

needed for tourism, agriculture,fish

processing,and urban/municipal

users,as well as natural ecosystems.

On many islands, water resources or

access to them are already limited

and subject to competing demands.

It is possible that climate change and

the resulting sea-level rise will

adversely affect water supplies in the

future through more frequent

droughts, floods,and salt water intrusion into freshwater lenses. The populations of the Pacific Islands are primarily concerned with future conditions that are likely to exacerbate

drought. In Puerto Rico and the US

Virgin Islands drought is also a concern,as are flooding and landslides

associated with heavy precipitation

events.

Adaptations: Strategies for providing

adequate water resources include

improved rainfall catchment;

improved storage and distribution

systems;development of under-utilized or alternative sources,better

management of water supply and

infrastructure;increased water conservation programs;construction of

groundwater recharge basins for

runoff;more effective use of ENSO

forecast information;and application

of new technology,such as desalinization. For agriculture,strategies

include exploring the feasibility of

planting more drought-resistant

crops.Consideration of the effects of

climate change and variability on

freshwater resources should be integrated into community planning and

tourism develpment.

Public Health and Safety

oth coastal and inland island

populations and infrastructure

are already at risk from climate

extremes. Storms can damage or

destroy buildings,damage infrastructure,and disrupt public services.

Both the Pacific and Caribbean

regions are familiar with severe

cyclones,which have caused billions

of dollars in damage from the

destruction of housing, agriculture,

roads and bridges,and lost tourism

revenue. In both regions,a large percentage of people,infrastructure,and

economic activities are located near

the coast,leading to dense areas of

vulnerability. The unique topography

of Puerto Rico and the Virgin Islands

makes them susceptible to floods and

landslides often resulting from severe

storms. It is possible that the frequency of extreme events may

increase over the next few decades to

a century thereby increasing the risk

to public health and safety.

Adaptations: Strategies include

upgrading and protection of infrastructure,comprehensive disaster

management programs, changes in

land use policies,and adoption and

enforcement of more stringent building codes. For reducing public health

risks,strategies include improved sanitation and health care infrastructure,

emergency plans,and public education about health risks posed by

floods and droughts.

82

ISLANDS IN THE CARIBBEAN 

AND THE PACIFIC KEY ISSUES

A

B

Freshwater

Lens

Saltwater Saltwater

Freshwater Lens Effect in Island Hydrology

On many islands, the underground pool of freshwater that

takes the shape of a lens is a critical water source. The freshwater lens is suspended by salt water. If sea level increases,

and/or if the lens becomes depleted because of excess withdrawals, salt water from the sea can intrude, making the water

unsuitable for many uses. The size of the lens is directly related to the size of the island: larger islands have lenses that are

less vulnerable to tidal mixing and have enough storage for

withdrawals. Smaller island freshwater lenses shrink during

prolonged periods of low rainfall, and water quality is easily

impaired by mixing with salt water. Short and light rainfall contributes little to recharge of these sources. Long periods of

rainfall are needed to provide adequate recharge.

Path of Hurricane Georges in Relation to

Puerto Rico with Precipitation Totals 

On September 21, 1998, Hurricane Georges swept across Puerto Rico. The eye of

the hurricane was 25-30 miles wide and passed within 15 miles of the capital, San

Juan, leaving a trail of devastation in its wake. The path of the hurricane and rainfall

totals are shown here. Some areas received up to 26 inches of rain within 24 hours.

Flooding, landslides, and catastrophic losses in infrastructure resulted.
Ecosystems and Biodiversity

he isolation of islands has made

them living laboratories for

understanding species adaptation and

evolution,but has also made them

extremely vulnerable to invasive

species and other stresses. Islands

are home to unique ecosystems and

species,with unsurpassed biodiversity. These resources are already threatened by invasive non-native plant and

animal species,as well as urban

expansion and various industrial

activities,resulting in the highest

extinction rates of all regions of the

US. They can also be highly climatesensitive. For example,coral bleaching associated with El Niño events

and the long-term warming of surface

waters has become widespread in

both the Pacific and Caribbean since

the 1990s. During the El Niño of

1997-98,coral bleaching in Palau,

known for its spectacular coral reefs,

was extensive.

Other possible concerns include

increased extinction rates of mountain species that have limited opportunities for migration;increased rates

of changes in mangrove ranges and

health;and declines in forests due to

floods,droughts,or increased incidence of pests,pathogens,or fire. It

is possible that increases in the frequency or intensity of hurricanes

would generally favor invasive

species. In addition,the unique

“cloud forests”located on some of

the islands occupy a narrow geographical and climatological niche. A

slight shift in temperature or precipitation patterns would possibly cause

this zone to shift upwards enough to

be eliminated.

Adaptations: While options are limited,strategies include efforts at slowing biological invasions,strengthening and enforcing policies that protect critical habitats,improving

understanding of the local effects of

climate variability and change,and

increasing the awareness of tourists

and the public concerning the value

of species and biodiversity.

Sea-level Variability

ea-level rise,both long-term and

episodic,is already an extremely

important issue for many of the

islands.Sea-level rise results in coastal

erosion.inundation,and salt water

intrusion into freshwater lenses and

coastal agricultural zones (where

taro,pulaka,and yams are grown).

Future sea-level rise,both global and

due to episodic events (such as

extreme lunar tides,ENSO-related

changes,and storm-related wave conditions) will increasingly contribute

to negative consequences for island

populations and ecosystems. Most at

risk are low-lying islands and atolls.

Examples of sites that are already

close to sea level include the

Republic of the Marshall Islands in

the Pacific and much of the metropolitan area of San Juan in Puerto Rico.

Adaptations: Strategies include

efforts to protect coastal infrastructure,transportation and water systems, agriculture,and communities;

integrated coastal zone management;

and crop diversification and the use

of salt-resistant crops. Retreat from

risk prone areas is likely to be necessary in some cases,but will be complicated due to land ownership,and

could have significant consequences

for social and cultural identity.

83

T

S

El Niños and La Niñas

Observed and Projected Sea Surface Temperature Anomalies 

With Projected Increases of

Historical CO2 and Sulfates (1990-2100) (1860-1990)

Sea Surface Temperature Anomaly (SSTA oC) Sea Surface Temperature Anomaly (SSTA oC)

Some model projections suggest more frequent El Niño-like conditions and stronger La Niñas as a result of climate change. Sea surface temperature (SST) deviations from normal in the equatorial Pacific are used to measure the strength of El Niños and La Niñas. These high resolution model

projections by the Max Planck Institute suggest more SST deviations from normal and thus more frequent El Niños and stronger La Niñas in the

future. The high bars in the center are occurrences of normal SSTs. In the projections in the right hand graph, these normal temperatures occur

less frequently, while lower (La Niña) and higher (El Niño) SSTs occur more frequently. The Max Planck model is used here because it has been

able to reproduce the strength of these events better than other models due to its physics and ability to resolve fine scale structure in the ocean.