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This Overview section

More detailed chapter from  "Foundation" report.

The National Assessment Overview and Foundation Reports were produced  by the National Assessment Synthesis Team, an advisory committee chartered under the Federal Advisory Committee Act, and were not subjected to OSTP's Information Quality Act Guidelines. The National Assessment was forwarded to the President and Congress in November 2000 for their consideration.

For background information on scenarios used in this assessment, see About Scenarios and Uncertainty and  Tools for Assessing Climate Change Impacts

Some models suggest more persistent El Niño-like conditions across the Pacific.

KEY ISSUES • Freshwater Resources • Public Health and Safety • Ecosystems and Biodiversity • Sea-level Variability

The 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.

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

Adequate 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 development.

Public Health and Safety

Both 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.

 

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

�Jack Jeffery Endangered Hawaiian hakalau.

The 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 climate-sensitive. 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.

�P.Grabhorn Coral reef ecosystem.

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.

 

�P. Grabhorn Mangrove

 

Sea-level Variability

Sea-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.

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 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. 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.