Small islands have characteristics which make them especially vulnerable to the effects of climate change, sea-level rise and extreme events (very high confidence).
These include their limited size and proneness to natural hazards and external shocks. They have low adaptive capacity, and adaptation costs are high relative to GDP [16.5].
Sea-level rise is likely to exacerbate inundation, storm surge, erosion and other coastal hazards, thus threatening the vital infrastructure that supports the socio-economic well-being of island communities (very high confidence).
Some studies suggest that sea-level rise could cause coastal land loss and inundation, while others show that some islands are morphologically resilient and are expected to persist [16.4.2]. In the Caribbean and Pacific Islands, more than 50% of the population live within 1.5 km of the shore. Almost without exception, the air and sea ports, major road arteries, communication networks, utilities and other critical infrastructure in the small islands of the Indian and Pacific Oceans and the Caribbean tend to be restricted to coastal locations (Table TS.2). The threat from sea-level rise is likely to be amplified by changes in tropical cyclones [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. Many small islands in the Caribbean and Pacific are likely to experience increased water stress as a result of climate change [16.4.1]. Predictions under all SRES scenarios for this region show reduced rainfall in summer, so that it is unlikely that demand will be met during low rainfall periods. Increased rainfall in winter will be unlikely to compensate, due to a lack of storage and high runoff during storms [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 NiÒo-Southern Oscillation (ENSO) events are likely to have severe impacts on commercial and artisanal fisheries. Increasing sea surface temperature and sea level, increased turbidity, nutrient loading and chemical pollution, damage from tropical cyclones, and decreases in growth rates due to the effects of higher CO2-concentrations on ocean chemistry, are very likely to lead to coral bleaching and mortality [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 (see Table TS.2). Increases in extreme events in the short term are virtually certain to affect the adaptation responses of forests on tropical islands, where regeneration is often slow. In view of their small area, forests on many islands can easily be decimated by violent cyclones or storms. On some high-latitude islands it is likely that forest cover will increase [16.4.4, 15.4.2].
Table TS.2. Range of future impacts and vulnerabilities in small islands [B16.1]. These projections are summarised from studies using a range of scenarios including SRES and Third Assessment Report sea-level rise projections.
|Latitude ||Region and system at risk || Impacts and vulnerability |
Iceland and isolated Arctic islands of Svalbard and the Faroe Islands: Marine ecosystem and plant species
The imbalance of species loss and replacement leads to an initial loss in diversity. Northward expansion of dwarf-shrub and tree-dominated vegetation into areas rich in rare endemic species results in their loss.
Large reduction in, or even a complete collapse of, the Icelandic capelin stock leads to considerable negative impacts on most commercial fish stocks, whales and seabirds.
|High-latitude islands (Faroe Islands): Plant species |
- Scenario I (temperature increase 2°C): species most affected by warming are restricted to the uppermost parts of mountains. For other species, the effect will mainly be upward migration.
- Scenario II (temperature decrease 2°C): species affected by cooling are those at lower altitudes.
|Sub-Antarctic Marion Islands: Ecosystem |
- Changes will directly affect the indigenous biota. An even greater threat is that a warmer climate will increase the ease with which the islands can be invaded by alien species.
|Five islands in the Mediterranean Sea: Ecosystems |
- Climate change impacts are negligible in many simulated marine ecosystems.
- Invasion into island ecosystems becomes an increasing problem. In the longer term, ecosystems will be dominated by exotic plants irrespective of disturbance rates.
|Mediterranean: Migratory birds (pied flycatchers: Ficedula hypoleuca) |
- Reduction in nestling and fledgling survival rates of pied flycatchers in two of the southernmost European breeding populations.
|Pacific and Mediterranean: Sim weed (Chromolaena odorata) |
- Pacific Islands at risk of invasion by sim weed.
- Mediterranean semi-arid and temperate climates predicted to be unsuitable for invasion.
|Pacific small islands: Coastal erosion, water resources and human settlements |
- Accelerated coastal erosion, saline intrusion into freshwater lenses and increased flooding from the sea cause large effects on human settlements.
- Lower rainfall coupled with accelerated sea-level rise compounds the threat on water resources; a 10% reduction in average rainfall by 2050 is likely to correspond to a 20% reduction in the size of the freshwater lens on Tarawa Atoll, Kiribati.
|American Samoa, fifteen other Pacific, Islands: Mangroves |
- 50% loss of mangrove area in American Samoa; 12% reduction in mangrove area in fifteen other Pacific Islands.
|Caribbean (Bonaire, Nether-lands Antilles): Beach erosion and sea-turtle nesting habitats |
- On average, up to 38% (±24% standard deviation) of the total current beach could be lost with a 0.5 m rise in sea level, with lower narrower beaches being the most vulnerable, reducing turtle nesting habitat by one-third.
| ||Caribbean (Bonaire, Barbados): Tourism |
- The beach-based tourism industry in Barbados and the marine-diving-based ecotourism industry in Bonaire are both negatively affected by climate change through beach erosion in Barbados and coral bleaching in Bonaire.
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, sea-water intrusion into freshwater lenses, soil salinisation and a decline in water supply will very likely 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, 15.4.2].
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 are likely to contribute to accelerated beach erosion, degradation of coral reefs and bleaching (Table TS.2). In addition, loss of cultural heritage from inundation and flooding will reduce 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 are also likely to 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 lie in tropical or sub-tropical zones with weather conducive to the transmission of diseases such as malaria, dengue, filariasis, schistosomiasis, and food- and water-borne diseases. Outbreaks of climate-sensitive diseases can be costly in terms of lives and economic impact. Increasing temperatures and decreasing water availability due to climate change are likely to increase the burdens of diarrhoeal and other infectious diseases in some small-island states [16.4.5].