Ecosystems: Although projected temperature rise is not anticipated to have widespread adverse consequences, some critical ecosystems, such as coral reefs, are very sensitive to temperature changes. Although some reefs have the ability to keep pace with the projected rate of sea-level rise, in many parts of the tropics (e.g., the Caribbean Sea, the Pacific Ocean) some species of corals live near their limits of temperature tolerance. Elevated seawater temperatures (above seasonal maxima) can seriously damage corals by bleaching and also impair their reproductive functions, and lead to increased mortality. The adaptive capacity of mangroves to climate change is expected to vary by species, as well as according to local conditions (e.g., the presence or absence of sediment-rich, macrotidal environments, the availability of adequate fresh water to maintain the salinity balance). The natural capacity of mangroves to adapt and migrate landward also is expected to be reduced by coastal land loss and the presence of infrastructure in the coastal zone. On some islands, ecosystems already are being harmed by other anthropogenic stresses (e.g., pollution), which may pose as great a threat as climate change itself. Climate change would add to these stresses and further compromise the long-term viability of these tropical ecosystems.

Hydrology and Water Resources: Freshwater shortage is a serious problem in many small island states, and many such states depend heavily on rainwater as the source of water. Changes in the patterns of rainfall may cause serious problems to such nations.

Coastal Systems: Higher rates of erosion and coastal land loss are expected in many small islands as a consequence of the projected rise in sea level. In the case of Majuro atoll in the Marshall Islands and Kiribati, it is estimated that for a 1-m rise in sea level as much as 80 per cent and 12.5 per cent (respectively) of total land would be vulnerable. Generally, beach sediment budgets are expected to be adversely affected by reductions in sediment deposition. On high islands, however, increased sediment yield from streams will help to compensate for sand loss from reefs. Low-lying island states and atolls also are expected to experience increased sea flooding, inundation and salinization (of soils and freshwater lenses) as a direct consequence of sea-level rise.

Human Settlements and Infrastructure: In a number of islands, vital infrastructure and major concentrations of settlements are likely to be at risk, given their location at or near present sea level and their proximity to the coast (often within 1-2 km; e.g., Kiribati, Tuvalu, the Maldives, the Bahamas). Moreover, vulnerability assessments also suggest that shore and infra-structure protection costs could be financially burdensome for some small island states.

Human Health: Climate change is projected to exacerbate health problems such as heat-related illness, cholera, dengue fever and biotoxin poisoning, and would place additional stress on the already over-extended health systems of most small islands.

Tourism: Tourism is the dominant economic sector in a number of small island states in the Caribbean Sea and the Pacific and Indian Oceans. In 1995, tourism accounted for 69 per cent, 53 per cent, and 50 per cent of gross national product (GNP) in Antigua, the Bahamas and the Maldives, respectively. This sector also earns considerable foreign exchange for a number of small island states, many of which are heavily dependent on imported food, fuel and a range of other vital goods and services. Foreign exchange earnings from tourism also provided more than 50 per cent of total revenues for some countries in 1995. Climate change and sea-level rise would affect tourism directly and indirectly: loss of beaches to erosion and inundation, salinization of freshwater aquifers, increasing stress on coastal ecosystems, damage to infrastructure from tropical and extra-tropical storms, and an overall loss of amenities would jeopardize the viability and threaten the long-term sustainability of this important industry in many small islands.

Conclusions: To evaluate the vulnerability of these island states to projected climate change, a fully integrated approach to vulnerability assessments is needed. The interaction of various bio-physical attributes (e.g., size, elevation, relative isolation) with the islands' economic and sociocultural character ultimately determines the vulnerability of these islands. Moreover, some islands are prone to periodic nonclimate-related hazards (e.g., earthquakes, volcanic eruptions, tsunamis); the overall vulnerability of these islands cannot be accurately evaluated in isolation from such threats. Similarly, vulnerability assessments for these small island states should take into consideration the value of nonmarketed goods and services (e.g., subsistence assets, community structure, traditional skills and knowledge), which also may be at risk from climate change. In some island societies, these assets are just as important as marketed goods and services.

Uncertainties in climate change projections may discourage adaptation, especially because some options may be costly or require changes in societal norms and behavior. As a guiding principle, policies and development programmes which seek to use resources in a sustainable manner, and which can respond effectively to changing conditions such as climate change, would be beneficial to the small island states, even if climate change did not occur.

The small island states are extremely vulnerable to global climate change and global sea-level rise. A range of adaptation strategies are theoretically possible. On some small low-lying island states and atolls, however, retreat away from the coasts is not an option. In some extreme cases, migration and resettlement outside of national boundaries might have to be considered.