The small island states considered in this chapter are located mainly in the tropics and the subtropics. These island states span the ocean regions of the Pacific, Indian, and Atlantic, as well as the Caribbean and Mediterranean Seas. Because of the very nature of these states, the ocean exerts a major influence on their physical, natural, and socioeconomic infrastructure and activities.

Although small island states are not a homogeneous group, they share many common features that serve to increase their vulnerability to projected impacts of climate change. These characteristics include their small physical size and the fact that they are surrounded by large expanses of ocean; limited natural resources; proneness to natural disasters and extreme events; relative isolation; extreme openness of their economies, which are highly sensitive to external shocks; large populations with high growth rates and densities; poorly developed infrastructure; and limited funds, human resources, and skills. These characteristics limit the capacity of small island states to mitigate and adapt to future climate and sea-level change.

The most significant and immediate consequences for small island states are likely to be related to changes in sea levels, rainfall regimes, soil moisture budgets, and prevailing winds (speed and direction) and short-term variations in regional and local patterns of wave action. Owing to their coastal location, the majority of socioeconomic activities and infrastructure and the population are likely to be highly vulnerable to the impacts of climate change and sea-level rise.

Review of past and present trends of climate and climate variability indicates that temperatures have been increasing by as much as 0.1°C per decade, and sea level has risen by 2 mm yr^-1 in regions in which small island states are located. Analysis of observational data for these regions suggests that increases in surface air temperatures have been greater than global rates of warming (e.g., in the Pacific Ocean and the Caribbean Sea regions). Observational evidence also suggests that much of the variability in the rainfall record of Caribbean and Pacific islands appears to be closely related to the onset of El Niño-Southern Oscillation (ENSO). However, part of the variability in these areas also may be attributable to the influence of the Inter-Tropical Convergence Zone (ITCZ) and the South Pacific Convergence Zone (SPCZ). It is acknowledged however, that for some small islands it is difficult to establish clear trends of sea-level change because of limitations of observational records, especially geodetic-controlled tide gauge records.

The use of the state-of-the-art coupled atmosphere-ocean general circulation models (AOGCMs) to estimate future response of climate to anthropogenic radiative forcing suggests an enhanced climate change in the future. Several AOGCMs have been analyzed for the Atlantic, Pacific, and Indian Ocean regions and the Caribbean and Mediterranean Seas. The outputs from these models indicate general increases in surface air temperature for the 2050s and 2080s and an increase in rainfall of about 0.3% for the 2050s and 0.7% for the 2080s for the Pacific region. However, a marginal decline in rainfall is projected for the other regions, with a possible reduction of water availability. The diurnal temperature range is projected to decrease marginally for the regions of the small island states for both time horizons.

With respect to extreme events, AOGCM (CSIRO and ECHAM) transient experiments project that by the 2050s and 2080s, there will be increased thermal stress during summer, as well as more frequent droughts and floods in all four tropical ocean regions in which small island states are located.This projection implies that in the future these regions are likely to experience floods during wet seasons and droughts during dry seasons. Furthermore, warming in some regions (e.g., the Pacific Ocean) is likened to an El Niño pattern, suggesting that climate variability associated with the ENSO phenomenon will continue on a seasonal and decadal time scale. It is probable that such an association may dominate over any effects attributable to global warming. Given their high vulnerability and low adaptive capacity to climate change, communities in the small island states have legitimate concerns about their future on the basis of the past observational record and climate model projections. In this Third Assessment Report, analysis of the scientific-technical literature identifies the following key issues among the priority concerns of small island states.

Development, sustainability, and equity issues. The small island states account for less than 1% of global greenhouse gas (GHG) emissions but are among the most vulnerable of all locations to the potential adverse effects of climate change and sea-level rise. Economic development and alleviation of poverty constitute the single most critical concern of many small island states. Thus, with limited resources and low adaptive capacity, these islands face the considerable challenge of meeting the social and economic needs of their populations in a manner that is sustainable. At the same time, they are forced to implement appropriate strategies to adapt to increasing threats resulting from greenhouse gas forcing of the climate system, to which they contribute little.

Sea-level rise. Although there will be regional variation in the signal, it is projected that sea level will rise by as much as 5 mm yr^-1 over the next 100 years as a result of GHG-induced global warming. This change in sea level will have serious consequences for the social and economic development of many small island states. For some islands, the most serious consideration will be whether they will have adequate potential to adapt to sea-level rise within their own national boundaries.

Beach and coastal changes. Most coastal changes currently experienced in the small island states are attributable to human activity. With the projected increase in sea level over the next 50-100 years superimposed on further shoreline development, however, the coastal assets of these states will be further stressed. This added stress, in turn, will increase the vulnerability of coastal environments by reducing natural resilience, while increasing the economic and social "costs" of adaptation.

Biological systems. Coral reefs, mangroves, and seagrass beds, which provide the economic foundation for many small islands, often rely on "stable" coastal environments to sustain themselves. Although it is acknowledged that human-induced stresses are contributing to their degradation, these systems will be adversely affected by rising air temperature and sea levels. In most small islands, coral reefs already are undergoing great stress from episodic warming of the sea surface, causing widespread bleaching. Mangroves—which are common on low-energy, nutrient/sediment-rich coasts and embayments in the tropics—have been altered by human activities. Changes in sea levels are likely to affect landward and longshore migration of remnants of mangrove forests, which provide some protection for the coasts and backshore infrastructure. It is projected that changes in the availability of sediment supply, coupled with increases in temperature and water depth as a consequence of sea-level rise, will adversely impact the productivity and physiological functions of seagrasses. Consequently, this would have a negative downstream effect on fish populations that feed on these communities.

Biodiversity. It is estimated that 33% of known threatened plants are island endemics, and 23% of bird species found on islands also are threatened. Although there is still some uncertainty about precisely how and to what extent biodiversity and wildlife in small islands will be affected, available projections suggest that climate change and sea-level rise will cause unfavorable shifts in biotic composition and adversely affect competition among some species.

Water resources, agriculture, and fisheries. The availability of water resources and food remain critical concerns in island communities. In many countries, water already is in short supply because islands (many of which are drought-prone) rely heavily on rainwater from small catchments or limited freshwater lenses. Arable land for crop agriculture often is in short supply; thus, the likely prospect of land loss and soil salinization as a consequence of climate change and sea-level rise will threaten the sustainability of both subsistence and commercial agriculture in these islands. Because water resources and agriculture are so climate sensitive, it is expected that these sectors also will be adversely affected by future climate and sea-level change. Although climate change is not expected to have a significant impact on world fisheries output, it is projected to have a severe impact on the abundance and distribution of reef fish population on the islands.

Human health, settlement and infrastructure, and tourism. Several human systems are likely to be affected by projected changes in climate and sea levels in many small island states. Human health is a major concern in many tropical islands, which currently are experiencing a high incidence of vector- and water-borne diseases. This is attributable partly to changes in temperature and rainfall, which may be linked to the ENSO phenomenon, and partly to changes in the patterns of droughts and floods. Climate extremes also place a huge burden on human welfare; this burden is likely to increase in the future. Almost all settlements, socioeconomic infrastructure, and activities such as tourism in many island states are located at or near coastal areas. Their location alone renders them highly vulnerable to future climate change and sea-level rise. Tourism is a major revenue earner and generates significant employment in many small islands. Changes in temperature and rainfall regimes, as well as loss of beaches, could be devastating for the economies that rely on this sector. Because climate change and sea-level rise are inevitable in the future, it is vital that beach and coastal assets in the small island states are managed wisely. Integrated coastal management has been identified and proposed as an effective framework for accomplishing this goal.

Sociocultural and traditional assets. Other island assets, such as know-how and traditional skills (technologies), are under threat from climate change and sea-level rise. In some societies, community structures and assets such as important traditional sites of worship, ritual, and ceremony—particularly those at or near the coasts—could be adversely affected by future climate change and sea-level rise.

It is significant to note that although many vulnerability assessment methodologies have been applied to different regions of the world with varying degrees of success, global assessments have consistently identified the small island states as one of the most high-risk areas, irrespective of methodology employed. This evidently robust finding must be of considerable concern to these states. It is further established that climate change is inevitable as a result of past GHG emissions and that small islands are likely to suffer disproportionately from the enhanced effects of climate change and sea-level rise. Hence, identification and implementation of effective adaptation measures and avoidance of maladaptation ( i.e., measures that increase exposure rather than decrease vulnerability) are critical for small islands, even if there is swift implementation of any global agreement to reduce future emissions.

For most small islands, the reality of climate change is just one of many serious challenges with which they are confronted. Such pressing socioeconomic concerns as poverty alleviation; high unemployment; and the improvement of housing, education, and health care facilities all compete for the slender resources available to these countries. In these circumstances, progress in adaptation to climate change almost certainly will require integration of appropriate risk reduction strategies with other sectoral policy initiatives in areas such as sustainable development planning, disaster prevention and management, integrated coastal management, and health care planning.

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