Executive summary 689
16.1 Introduction 690
16.2 Current sensitivity and vulnerability 690
16.2.1 Special characteristics of small islands 690
16.2.2 Climate and weather 691
16.2.3 Other stresses 692
16.2.4 Current adaptation 694
16.3 Assumptions about future trends 694
16.3.1 Climate and sea-level change 694
16.3.2 Other relevant conditions 695
16.4 Key future impacts and vulnerabilities 695
16.4.1 Water resources 695
Box 16.1 Range of future impacts and vulnerabilities in small islands 696
16.4.2 Coastal systems and resources 697
16.4.3 Agriculture, fisheries and food security 698
Box 16.2 Non-climate-change threats to coral reefs of small islands 699
16.4.4 Biodiversity 700
16.4.5 Human settlements and well-being 700
16.4.6 Economic, financial and socio-cultural impacts...701 Box 16.3 Grenada and Hurricane Ivan 702
16.4.7 Infrastructure and transportation 702
16.5 Adaptation: practices, options and constraints 703
16.5.1 Role of adaptation in reducing vulnerability and impacts 703
16.5.2 Adaptation options and priorities:
examples from small island states 703
Box 16.4 Future island conditions and well-being:
the value of adaptation 704
Box 16.5 Adaptive measures in the Maldives 705
16.5.3 Adaptation of 'natural' ecosystems in island environments 706
16.5.4 Adaptation: constraints and opportunities 706
Box 16.6 Climate dangers and atoll countries 707
16.5.5 Enhancing adaptive capacity 708
16.6 Conclusions: implications for sustainable development 709
Box 16.7 Capacity building for development of adaptation measures in small islands: a community approach 710
16.7 Key uncertainties and research gaps 711
16.7.1 Observations and climate change science 711
16.7.2 Impacts and adaptation 711
Small islands, whether located in the tropics or higher latitudes, have characteristics which make them especially vulnerable to the effects of climate change, sea-level rise, and extreme events (very high confidence).
This assessment confirms and strengthens previous observations reported in the IPCC Third Assessment Report (TAR) which show that characteristics such as limited size, proneness to natural hazards, and external shocks enhance the vulnerability of islands to climate change. In most cases they have low adaptive capacity, and adaptation costs are high relative to gross domestic product (GDP). [16.1, 16.5]
Sea-level rise is expected to exacerbate inundation, storm surge, erosion and other coastal hazards, thus threatening vital infrastructure, settlements and facilities that support the livelihood of island communities (very high confidence).
Some studies suggest that sea-level rise could lead to a reduction in island size, particularly in the Pacific, whilst others show that a few islands are morphologically resilient and are expected to persist. Island infrastructure tends to predominate in coastal locations. In the Caribbean and Pacific islands, more than 50% of the population live within 1.5 km of the shore. Almost without exception, international airports, roads and capital cities in the small islands of the Indian and Pacific Oceans and the Caribbean are sited along the coast, or on tiny coral islands. Sea-level rise will exacerbate inundation, erosion and other coastal hazards, threaten vital infrastructure, settlements and facilities, and thus compromise the socio-economic well-being of island communities and states. [16.4.2,16.4.5,16.4.7]
There is strong evidence that under most climate change scenarios, water resources in small islands are likely to be seriously compromised (very high confidence).
Most small islands have a limited water supply, and water resources in these islands are especially vulnerable to future changes and distribution of rainfall. Many islands in the Caribbean are likely to experience increased water stress as a result of climate change. Under all Special Report on Emissions Scenarios (SRES) scenarios, reduced rainfall in summer is projected for this region, so that it is unlikely that demand would be met during low rainfall periods. Increased rainfall in winter is unlikely to compensate, due to lack of storage and high runoff during storms. In the Pacific, a 10% reduction in average rainfall (by 2050) would lead to a 20% reduction in the size of the freshwater lens on Tarawa Atoll, Kiribati. Reduced rainfall coupled with sea-level rise would compound this threat. Many small islands have begun to invest in the implementation of adaptation strategies, including desalination, to offset current and projected water shortages. [16.4.1]
Climate change is likely to heavily impact coral reefs, fisheries and other marine-based resources (high confidence).
Fisheries make an important contribution to the GDP of many island states. Changes in the occurrence and intensity of El Nino-Southern Oscillation (ENSO) events are likely to have severe impacts on commercial and artisanal fisheries. Increasing sea surface temperature and rising sea level, increased turbidity, nutrient loading and chemical pollution, damage from tropical cyclones, and decreases in growth rates due to the effects of higher carbon dioxide concentrations on ocean chemistry, are very likely to affect the health of coral reefs and other marine ecosystems which sustain island fisheries. Such impacts will exacerbate non-climate-change stresses on coastal systems. [16.4.3]
On some islands, especially those at higher latitudes, warming has already led to the replacement of some local species (high confidence).
Mid- and high-latitude islands are virtually certain to be colonised by non-indigenous invasive species, previously limited by unfavourable temperature conditions. Increases in extreme events are virtually certain to affect the adaptation responses of forests on tropical islands, where regeneration is often slow, in the short term. In view of their small area, forests on many islands can easily be decimated by violent cyclones or storms. However, it is possible that forest cover will increase on some high-latitude islands. [16.4.4, 184.108.40.206]
It is very likely that subsistence and commercial agriculture on small islands will be adversely affected by climate change (high confidence).
Sea-level rise, inundation, seawater intrusion into freshwater lenses, soil salinisation, and decline in water supply are very likely to adversely impact coastal agriculture. Away from the coast, changes in extremes (e.g., flooding and drought) are likely to have a negative effect on agricultural production. Appropriate adaptation measures may help to reduce these impacts. In some high-latitude islands, new opportunities may arise for increased agricultural production. [16.4.3, 220.127.116.11]
New studies confirm previous findings that the effects of climate change on tourism are likely to be direct and indirect, and largely negative (high confidence).
Tourism is the major contributor to GDP and employment in many small islands. Sea-level rise and increased sea water temperature will cause accelerated beach erosion, degradation of coral reefs, and bleaching. In addition, a loss of cultural heritage from inundation and flooding reduces the amenity value for coastal users. Whereas a warmer climate could reduce the number of people visiting small islands in low latitudes, it could have the reverse effect in mid- and high-latitude islands. However, water shortages and increased incidence of vector-borne diseases may also deter tourists. [16.4.6]
There is growing concern that global climate change is likely to impact human health, mostly in adverse ways (medium confidence).
Many small islands are located in tropical or sub-tropical zones whose weather and climate are already conducive to the transmission of diseases such as malaria, dengue, filariasis, schistosomiasis, and food- and water-borne diseases. Other climate-sensitive diseases of concern to small islands include diarrhoeal diseases, heat stress, skin diseases, acute respiratory infections and asthma. The observed increasing incidence of many of these diseases in small islands is attributable to a combination of factors, including poor public health practices, inadequate infrastructure, poor waste management practices, increasing global travel, and changing climatic conditions. [16.4.5]
While acknowledging their diversity, the IPCC Third Assessment Report (TAR) also noted that small island states share many similarities (e.g., physical size, proneness to natural disasters and climate extremes, extreme openness of their economies, low adaptive capacity) that enhance their vulnerability and reduce their resilience to climate variability and change.
Analysis of observational data showed a global mean temperature increase of around 0.6°C during the 20th century, while mean sea level rose by about 2 mm/yr, although sea-level trends are complicated by local tectonics and El Nino-Southern Oscillation (ENSO) events. The rate of increase in air temperature in the Pacific and Caribbean during the 20th century exceeded the global average. The TAR also found much of the rainfall variability appeared to be closely related to ENSO events, combined with seasonal and decadal changes in the convergence zones.
Owing to their high vulnerability and low adaptive capacity, small islands have legitimate concerns about their future, based on observational records, experience with current patterns and consequences of climate variability, and climate model projections. Although emitting less than 1% of global greenhouse gases, many small islands have already perceived a need to reallocate scarce resources away from economic development and poverty alleviation, and towards the implementation of strategies to adapt to the growing threats posed by global warming (e.g., Nurse and Moore, 2005).
While some spatial variation within and among regions is expected, the TAR reported that sea level is projected to rise at an average rate of about 5.0 mm/yr over the 21st century, and concluded that sea-level change of this magnitude would pose great challenges and high risk, especially to low-lying islands that might not be able to adapt (Nurse et al., 2001). Given the sea level and temperature projections for the next 50 to 100 years, coupled with other anthropogenic stresses, the coastal assets of small islands (e.g., corals, mangroves, sea grasses and reef fish), would be at great risk. As the natural resilience of coastal areas may be reduced, the 'costs' of adaptation could be expected to increase. Moreover, anticipated land loss, soil salinisation and low water availability would be likely to threaten the sustainability of island agriculture and food security.
In addition to natural and managed system impacts, the TAR also drew attention to projected human costs. These included an increase in the incidence of vector- and water-borne diseases in many tropical and sub-tropical islands, which was attributed partly to temperature and rainfall changes, some linked to ENSO. The TAR also noted that most settlements and infrastructure of small islands are located in coastal areas, which are highly vulnerable not only to sea-level rise (SLR) but also to high-energy waves and storm surge. In addition, temperature and rainfall changes and loss of coastal amenities could adversely affect the vital tourism industry. Traditional knowledge and other cultural assets (e.g., sites of worship and ritual), especially those near the coasts, were also considered to be vulnerable to climate change and sea-level rise. Integrated coastal management was proposed as an effective management framework in small islands for ensuring the sustainability of coastal resources. Such a framework has been adopted in several island states. More recently, the Organisation of Eastern Caribbean States (OECS, 2000) has adopted a framework called 'island systems management', which is both an integrated and holistic (rather than sectoral) approach to whole-island management including terrestrial, aquatic and atmospheric environments.
The TAR concluded that small islands could focus their efforts on enhancing their resilience and implement appropriate adaptation measures as urgent priorities. Thus, integration of risk reduction strategies into key sectoral activities (e.g., disaster management, integrated coastal management and health care planning) should be pursued as part of the adaptation planning process for climate change.
Building upon the TAR, this chapter assesses recent scientific information on vulnerability to climate change and sea-level rise, adaptation to their effects, and implications of climate-related policies, including adaptation, for the sustainable development of small islands. Assessment results are presented in a quantitative manner wherever possible, with near, middle, and far time-frames in this century, although much of the literature concerning small islands is not precise about the time-scales involved in impact, vulnerability and adaptation studies. Indeed, independent scientific studies on climate change and small islands since the TAR have been quite limited, though there are a number of synthetic publications, regional resource books, guidelines, and policy documents including: Surviving in Small Islands: A Guide Book (Tompkins et al., 2005); Climate Variability and Change and Sea-level rise in the Pacific Islands Region: A Resource Book for Policy and Decision Makers, Educators and Other Stakeholders (Hay et al., 2003); Climate Change: Small Island Developing States (UNFCCC, 2005); and Not If, But When: Adapting to Natural Hazards in the Pacific Island Region: A Policy Note (Bettencourt et al., 2006).
These publications rely heavily on the TAR, and on studies undertaken by global and regional agencies and contracted reports. It is our qualitative view that the volume of literature in refereed international journals relating to small islands and climate change since publication of the TAR is rather less than that between the Second Assessment Report in 1995 and the TAR in 2001. There is also another difference in that the present chapter deals not only with independent small island states but also with non-autonomous small islands in the continental and large archipelagic countries, including those in high latitudes. Nevertheless the focus is still mainly on the autonomous small islands predominantly located in the tropical and sub-tropical regions; a focus that reflects the emphasis in the literature.
16.2 Current sensitivity and vulnerability
Many small islands are highly vulnerable to the impacts of climate change and sea-level rise. They comprise small land masses surrounded by ocean, and are frequently located in regions prone to natural disasters, often of a hydrometeorological and/or geological nature. In tropical areas they host relatively large populations for the area they occupy, with high growth rates and densities. Many small islands have poorly developed infrastructure and limited natural, human and economic resources, and often small island populations are dependent on marine resources to meet their protein needs. Most of their economies are reliant on a limited resource base and are subject to external forces, such as changing terms of trade, economic liberalisation, and migration flows. Adaptive capacity to climate change is generally low, though traditionally there has been some resilience in the face of environmental change.
16.2.2 Climate and weather
The climate regimes of small islands are quite variable, generally characterised by large seasonal variability in precipitation and by small seasonal temperature differences in low-latitude islands and large seasonal temperature differences in high-latitude islands. In the tropics, cyclones and other extreme climate and weather events cause considerable losses to life and property.
The climates of small islands in the central Pacific are influenced by several contributing factors such as trade wind regimes, the paired Hadley cells and Walker circulation, seasonally varying convergence zones such as the South Pacific Convergence Zone (SPCZ), semi-permanent sub-tropical high-pressure belts, and zonal westerlies to the south, with ENSO as the dominant mode of year-to-year variability (Fitzharris, 2001; Folland et al., 2002; Griffiths et al., 2003). The Madden-Julian Oscillation (MJO) is a major mode of variability of the tropical atmosphere-ocean system of the Pacific on time-scales of 30 to 70 days (Revell, 2004), while the leading mode of variability with decadal time-scale is the Interdecadal Pacific Oscillation (IPO) (Salinger et al., 2001). A number of studies suggest that the influence of global warming could be a major factor in accentuating the current climate regimes and the changes from the normal that come with ENSO events (Folland et al., 2003; Hay et al., 2003).
The climate of the Caribbean islands is broadly characterised by distinct dry and wet seasons with orography and elevation being significant modifiers on the sub-regional scale. The dominant influences are the North Atlantic Sub-tropical High (NAH) and ENSO. During the Northern Hemisphere winter, the NAH lies further south, with strong easterly trades on its equatorial flank modulating the climate and weather of the region. Coupled with a strong inversion, a cool ocean, and reduced atmospheric humidity, the region is generally at its driest during the Northern Hemisphere winter. With the onset of the Northern Hemisphere spring, the NAH moves northwards, the trade wind intensity decreases, and the region then comes under the influence of the equatorial trough.
In the Indian Ocean, the climate regimes of small islands in tropical regions are predominantly influenced by the Asian monsoon; the seasonal alternation of atmospheric flow patterns which results in two distinct climatic regimes: the south-west or summer monsoon and the north-east or winter monsoon, with a clear association with ENSO events.
The climates of small islands in the Mediterranean are dominated by influences from bordering lands. Commonly the islands receive most of their rainfall during the Northern Hemisphere winter months and experience a prolonged summer drought of 4 to 5 months. Temperatures are generally moderate with a comparatively small range of temperature between the winter low and summer high.
16222 Observed trends
New observations and reanalyses of temperatures averaged over land and ocean surfaces since the TAR show consistent warming trends in all small-island regions over the 1901 to 2004 period (Trenberth et al., 2007). However, the trends are not linear. Recent studies show that annual and seasonal ocean surface and island air temperatures have increased by 0.6 to 1.0°C since 1910 throughout a large part of the South Pacific, south-west of the SPCZ. Decadal increases of 0.3 to 0.5°C in annual temperatures have been widely seen only since the 1970s, preceded by some cooling after the 1940s, which is the beginning of the record, to the north-east of the SPCZ (Salinger, 2001; Folland etal., 2003).
For the Caribbean, Indian Ocean and Mediterranean regions, analyses shows warming ranged from 0 to 0.5°C per decade for the 1971 to 2004 period (Trenberth et al., 2007). Some high-latitude regions, including the western Canadian Arctic Archipelago, have experienced warming more rapid than the global mean (McBean et al., 2005).
Trends in extreme temperature across the South Pacific for the period 1961 to 2003 show increases in the annual number of hot days and warm nights, with decreases in the annual number of cool days and cold nights, particularly in the years after the onset of El Niño (Manton et al., 2001; Griffiths et al., 2003). In the Caribbean, the percentage of days having very warm maximum or minimum temperatures has increased considerably since the 1950s, while the percentage of days with cold temperatures has decreased (Peterson et al., 2002).
Analyses of trends in extreme daily rainfall across the South Pacific for the period 1961 to 2003 show extreme rainfall trends which are generally less spatially coherent than those of extreme temperatures (Manton et al., 2001; Griffiths et al., 2003). In the Caribbean, the maximum number of consecutive dry days is decreasing and the number of heavy rainfall events is increasing. These changes were found to be similar to the changes reported from global analysis (Trenberth et al., 2007).
Variations in tropical and extra-tropical cyclones, hurricanes and typhoons in many small-island regions are dominated by ENSO and decadal variability which result in a redistribution of tropical storms and their tracks, so that increases in one basin are often compensated by decreases in other basins. For example, during an El Niño event, the incidence of tropical storms typically decreases in the Atlantic and far-western Pacific and the Australian regions, but increases in the central and eastern Pacific, and vice versa. Clear evidence exists that the number of storms reaching categories 4 and 5 globally have increased since 1970, along with increases in the Power Dissipation Index (Emanuel, 2005) due to increases in their intensity and duration (Trenberth et al., 2007). The total number of cyclones and cyclone days decreased slightly in most basins. The largest increase was in the North Pacific, Indian and SouthWest Pacific oceans. The global view of tropical storm activity highlights the important role of ENSO in all basins. The most active year was 1997, when a very strong El Niño began, suggesting that the observed record sea surface temperatures (SSTs) played a key role (Trenberth et al., 2007). For extratropical cyclones, positive trends in storm frequency and intensity dominate during recent decades in most regional studies performed. Longer records for the North Atlantic suggest that the recent extreme period may be similar in level to that of the late 19th century (Trenberth et al., 2007).
In the tropical South Pacific, small islands to the east of the dateline are highly likely to receive a higher number of tropical storms during an El Niño event compared with a La Niña event and vice versa (Brazdil et al., 2002). Observed tropical cyclone activity in the South Pacific east of 160°E indicates an increase in level of activity, with the most active years associated with El Niño events, especially during the strong 1982/1983 and 1997/1998 events (Levinson, 2005). Webster et al. (2005) found more than a doubling in the number of category 4 and 5 storms in the South-West Pacific from the period 1975-1989 to the period 1990-2004. In the 2005/2006 season, La Niña influences shifted tropical storm activity away from the South Pacific region to the Australian region and, in March and April 2006, four category 5 typhoons occurred (Trenberth et al., 2007).
In the Caribbean, hurricane activity was greater from the 1930s to the 1960s, in comparison with the 1970s and 1980s and the first half of the 1990s. Beginning with 1995, all but two Atlantic hurricane seasons have been above normal (relative to the 1981-2000 baseline). The exceptions are the two El Niño years of 1997 and 2002. El Niño acts to reduce activity and La Niña acts to increase activity in the North Atlantic. The increase contrasts sharply with the generally below-normal seasons observed during the previous 25-year period, 1975 to 1994. These multi-decadal fluctuations in hurricane activity result almost entirely from differences in the number of hurricanes and major hurricanes forming from tropical storms first named in the tropical Atlantic and Caribbean Sea.
In the Indian Ocean, tropical storm activity (May to December) in the northern Indian Ocean has been near normal in recent years. For the southern Indian Ocean, the tropical cyclone season is normally active from December to April. A lack of historical record-keeping severely hinders trend analysis (Trenberth et al., 2007).
Analyses of the longest available sea-level records, which have at least 25 years of hourly data from 27 stations installed around the Pacific basin, show the overall average mean relative sea-level rise around the whole region is +0.77 mm/yr (Mitchell et al., 2001). Rates of relative sea level have also been calculated for the SEAFRAME stations in the Pacific. Using these results and focusing only on the island stations with more than 50 years of data (only four locations), the average rate of sea-level rise (relative to the Earth's crust) is 1.6 mm/yr (Bindoff et al., 2007). Church et al. (2004) used TOPEX/Poseidon altimeter data, combined with historical tide gauge data, to estimate monthly distributions of large-scale sea-level variability and change over the period 1950 to 2000. Church et al. (2004) observed the maximum rate of rise in the central and eastern Pacific, spreading north and south around the sub-tropical gyres of the Pacific Ocean near 90°E, mostly between 2 and 2.5 mm/yr but peaking at over 3 mm/yr. This maximum was split by a minimum rate of rise, less than 1.5 mm/yr, along the equator in the eastern Pacific, linking to the western Pacific just west of 180° (Christensen et al., 2007).
The Caribbean region experienced, on average, a mean relative sea-level rise of 1 mm/yr during the 20th century. Considerable regional variations in sea level were observed in the records; these were due to large-scale oceanographic phenomena such as El Niño coupled with volcanic and tectonic crustal motions of the Caribbean Basin rim, which affect the land levels on which the tide gauges are located. Similarly, recent variations in sea level on the west Trinidad coast indicate that sea level in the north is rising at a rate of about 1 mm/yr, while in the south the rate is about 4 mm/yr; the difference being a response to tectonic movements (Miller, 2005).
In the Indian Ocean, reconstructed sea levels based on tide gauge data and TOPEX/Poseidon altimeter records for the 1950 to 2001 period give rates of relative sea-level rise of 1.5,1.3 and 1.5 mm/yr (with error estimates of about 0.5 mm/yr) at Port Louis, Rodrigues, and Cocos Islands, respectively (Church et al., 2006). In the equatorial band, both the Male and Gan sea-level sites in the Maldives show trends of about 4 mm/yr (Khan et al., 2002), with the range from three tidal stations over the 1990s being from 3.2 to 6.5 mm/yr (Woodworth et al., 2002). Church et al. (2006) note that the Maldives has short records and that there is high variability between sites, and their 52-year reconstruction suggests a common rate of rise of 1.0 to 1.2 mm/yr.
Some high-latitude islands are in regions of continuing postglacial isostatic uplift, including parts of the Baltic, Hudson Bay, and the Canadian Arctic Archipelago (CAA). Others along the Siberian coast and the eastern and western margins of the CAA are subsiding. Although few long tide-gauge records exist in the region, relative sea-level trends are known to range from negative (falling relative sea level) in the central CAA and Hudson Bay to rates as high as 3 mm/yr or more in the Beaufort Sea (Manson et al., 2005). Available data from the Siberian sector of the Arctic Ocean indicate that late 20th century sea-level rise was comparable to the global mean (Proshutinsky et al., 2004).
Climate change and sea-level rise are not unique contributors to the extreme vulnerability of small islands. Other factors include socio-economic conditions, natural resource and space limitations, and the impacts of natural hazards such as tsunami and storms. In the Pacific, vulnerability is also a function of internal and external political and economic processes which affect forms of social and economic organisation that are different from those practiced traditionally, as well as attempts to impose models of adaptation that have been developed for Western economies, without sufficient thought as to their applicability in traditional island settings (Cocklin, 1999).
Socio-economic contributors to island vulnerability include external pressures such as terms of trade, impacts of globalisation (both positive and negative), financial crises, international conflicts, rising external debt, and internal local conditions such as rapid population growth, rising incidence of poverty, political instability, unemployment, reduced social cohesion, and a widening gap between poor and rich, together with the interactions between them (ADB, 2004).
Most settlements in small islands, with the exception of some of the larger Melanesian and Caribbean islands, are located in coastal locations, with the prime city or town also hosting the main port, international airport and centre of government activities. Heavy dependence on coastal resources for subsistence is also a major feature of many small islands.
Rapid and unplanned movements of rural and outer-island residents to the major centres is occurring throughout small islands, resulting in deteriorating urban conditions, with pressure on access to urban services required to meet basic needs. High concentrations of people in urban areas create various social, economic and political stresses, and make people more vulnerable to short-term physical and biological hazards such as tropical cyclones and diseases. It also increases their vulnerability to the impacts of climate change and sea-level rise (Connell, 1999, 2003).
Globalisation is also a major stress, though it has been argued that it is nothing new for many small islands, since most have had a long history of colonialism and, more latterly, experience of some of the rounds of transformation of global capitalism (Pelling and Uitto, 2001). Nevertheless, in the last few years, the rate of change and growth of internationalisation have increased, and small islands have had to contend with new forms of extra-territorial economic, political and social forces such as multinational corporations, transnational social movements, international regulatory agencies, and global communication networks. In the present context, these factors take on a new relevance, as they may influence the vulnerability of small islands and their adaptive capacity (Pelling and Uitto, 2001; Adger et al., 2003a).
Most small islands have limited sources of freshwater. Atoll countries and limestone islands have no surface water or streams and are fully reliant on rainfall and groundwater harvesting. Many small islands are experiencing water stress at the current levels of rainfall input, and extraction of groundwater is often outstripping supply. Moreover, pollution of groundwater is often a major problem, especially on low-lying islands. Poor water quality affects human health and carries water-borne diseases.
Water quality is just one of several health issues linked to climate variability and change and their potential effects on the well-being of the inhabitants of small islands (Ebi et al., 2006).
It is also almost inevitable that the ecological systems of small islands, and the functions they perform, will be sensitive to the rate and magnitude of climate change and sea-level rise, especially where exacerbated by human activities (e.g., ADB, 2004, in the case of the small islands in the Pacific). Both terrestrial ecosystems on the larger islands and coastal ecosystems on most islands have been subjected to increasing degradation and destruction in recent decades. For instance, analysis of coral reef surveys over three decades has revealed that coral cover across reefs in the Caribbean has declined by 80% in just 30 years, largely as a result of continued pollution, sedimentation, marine diseases, and over-fishing (Gardner et al., 2003).
External pressures that contribute to the vulnerability of small islands to climate change include energy costs, population movements, financial and currency crises, international conflicts, and increasing debt. Internal processes that create vulnerability include rapid population growth, attempts to increase economic growth through exploitation of natural resources such as forests, fisheries and beaches, weak infrastructure, increasing income inequality, unemployment, rapid urbanisation, political instability, a growing gap between demand for and provision of health care and education services, weakening social capital, and economic stagnation. These external and internal processes are related and interact in complex ways to heighten the vulnerability of island social and ecological systems to climate change.
Natural hazards of hydrometeorological origin remain an important stressor and cause impacts on the economies of small islands that are disproportionally large (Bettencourt et al., 2006). The devastation of Grenada following the passage of Hurricane Ivan on 7 September 2004 is a powerful illustration of the reality of small-island vulnerability (Nurse and Moore, 2005). In less than 8 hours, the country's vital socio-economic infrastructure, including housing, utilities, tourism-related facilities and subsistence and commercial agricultural production, suffered incalculable damage. The island's two principal foreign-exchange earners - tourism and nutmeg production - suffered heavily. More than 90% of hotel guest rooms were either completely destroyed or damaged, while more than 80% of the island's nutmeg trees were lost. One of the major challenges with regard to hydrometeorological hazards is the time it takes to recover from them. In the past it was common for socio-ecological systems to recover from hazards, as these were sufficiently infrequent and/or less damaging. In the future, climate change may create a situation where more intense and/or more frequent extreme events may mean there is less time in which to recover. Sequential extreme events may mean that recovery is never complete, resulting in long-term deteriorations in affected systems, e.g., declines in agricultural output because soils never recover from salinisation; urban water systems and housing infrastructure deteriorating because damage cannot be repaired before the next extreme event.
Past studies of adaptation options for small islands have largely focused on adjustments to sea-level rise and storm surges associated with tropical cyclones. There was an early emphasis on protecting land through 'hard' shore-protection measures rather than on other measures such as accommodating sea-level rise or retreating from it, although the latter has become increasingly important on continental coasts. Vulnerability studies conducted for selected small islands (Nurse et al., 2001) show that the costs of overall infrastructure and settlement protection are a significant proportion of GDP, and well beyond the financial means of most small island states; a problem not always shared by the islands of metropolitan countries (i.e., with high-density, predominantly urban populations). More recent studies since the TAR have identified major areas of adaptation, including water resources and watershed management, reef conservation, agricultural and forest management, conservation of biodiversity, energy security, increased development of renewable energy, and optimised energy consumption. Some of these are detailed in Section 16.5. Proposed adaptation strategies have also focused on reducing vulnerability and increasing resilience of systems and sectors to climate variability and extremes through mainstreaming adaptation (Shea et al., 2001; Hay et al., 2003; ADB, 2004; UNDP, 2005).
16.3 Assumptions about future trends
16.3.1 Climate and sea-level change
Since the TAR, future climate change projections have been updated (Ruosteenoja et al., 2003). These analyses reaffirm previous IPCC projections that suggest a gradual warming of SSTs and a general warming trend in surface air temperature in all small-island regions and seasons (Lal et al., 2002). However, it must be cautioned that, because of scaling problems, these projections for the most part apply to open ocean surfaces and not to land surfaces. Consequently the temperature changes may well be higher than current projections.
Projected changes in seasonal surface air temperature (Table 16.1) and precipitation (Table 16.2) for the three 30-year periods (2010 to 2039, 2040 to 2069 and 2070 to 2099) relative to the baseline period 1961 to 1990, have been prepared by Ruosteenoja et al. (2003) for all the sub-continental scale regions of the world, including small islands. They used seven coupled atmosphere-ocean general circulation models (AOGCMs), the greenhouse gas and aerosol forcing being inferred from the IPCC Special Report on Emissions Scenarios (SRES; Nakicenovic and Swart, 2000) A1FI, A2, B1 and B2 emissions scenarios.
All seven models project increased surface air temperature for all regions of the small islands. The Ruosteenoja et al. (2003) projected increases all lie within previous IPCC surface air temperature projections, except for the Mediterranean Sea. The increases in surface air temperature are projected to be more or less uniform in both seasons, but for the Mediterranean Sea, warming is projected to be greater during the summer than the winter. For the South Pacific, Lal (2004) has indicated that the surface air temperature by 2100 is estimated to be at least 2.5°C more than the 1990 level. Seasonal variations of projected warming are minimal. No significant change in diurnal temperature range is likely with a rise in surface temperatures. An increase in mean temperature would be accompanied by an increase in the frequency of extreme temperatures. High-latitude regions are likely to experience greater warming, resulting in decreased sea ice extent and increased thawing of permafrost (Meehl et al., 2007).
Regarding precipitation, the range of projections is still large, and even the direction of change is not clear. The models simulate only a marginal increase or decrease (10%) in annual rainfall over most of the small islands in the South Pacific. During summer, more rainfall is projected, while an increase in daily rainfall intensity, causing more frequent heavier rainfall events, is also likely (Lal, 2004).
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