A Changing Climate for Small Island States
Sea Level Rise and Climate Change: Impacts on Small Island States
Sea level rise is one of the most tangible and readily acknowledged consequences of climate change. By 2100, conservative estimates place global average sea level rise at approximately 1m (3 feet), with a more significant rise of 2-3 meters (6-10 feet) possible. Many small island countries are no higher than only a few meters above sea level, and are extremely vulnerable sea level rise. In addition, these states will suffer from a range of other impacts of climate change, including changes in precipitation patterns; groundwater salinization; higher sea surface temperatures; and ocean acidification. As these physical impacts of climate change interact with social and economic vulnerabilities, climate change poses a significant threat to the islands’ physical, social, and economic well-being.
Sea level rise is complex, and will not impact small island states uniformly: oceans are expected to rise at different rates in different parts of the world, and the effects of any rise will depend on other conditions specific to the island (for example, the health of mangrove forests or coral reefs which can protect against erosion). However, some impacts of sea level rise are very likely to affect small island states generally, including higher risk of erosion, and more frequent and severe flooding of low-lying and coastal areas.
Because of small islands’ high coastline to land area ratio, most of their human settlements, agricultural lands, and critical infrastructure (including airports, bridges, port facilities and road networks) are at or near the coasts. Coastal erosion will therefore be especially harmful to the islands’ economies and societies.
Potential changes in precipitation patterns and sea level rise collectively pose a threat to the islands’ supply of freshwater, which usually comes from limited groundwater sources and rainfall. A decrease in precipitation would decrease both the amount of rainwater collected directly and diminish the recharge of the freshwater lens which supplies groundwater, while increased intensity of precipitation could reduce soil fertility and lead to general soil degradation. Sea level rise can exacerbate ground water salinization, as salt water penetrates the groundwater and leaves it brackish. These physical impacts resulting from climate change would further compromise a water supply which is often already strained under the pressures of both domestic and agricultural demands.
Climate change is leading to higher sea surface temperatures, as well as increased ocean acidification, both of which threaten coral reefs. Coral reefs play a vital role in the overall health of tropical Pacific islands, as they help to protect against flooding and erosion and provide habitats for the fish and shellfish which provide sustenance and an income source for residents. Rising ocean temperatures lead to coral bleaching, and acidification leads to lower rates of calcification, both of which damage the health and growth of coral reefs. In addition, rising sea surface temperatures are expected to decrease fish catch, as changes in the temperature and salinity of ocean water lead to changes in the distribution and abundance of fish and to their migratory patterns.
The Vulnerability of Small Island States
Certain physical and socioeconomic characteristics common to small island states tend to intensify their vulnerability to climate change. A high ratio of coast line to land area, high population density, and minimal elevation above sea level puts large parts of the population at risk from storms, flooding and erosion. Scarce freshwater supplies are at risk from even relatively small shifts in precipitation patterns or sea level: for example, in Tarawa Atoll, Kiribati, the combination of a 25% reduction in rainfall and 50 cm of sea level rise is expected to reduce the size of the freshwater lens by 65%. In addition, small island states often depend on coastal ecosystems, including mangroves and coral reefs, for household income, revenue from tourism, and food. These ecosystems are threatened by rising sea surface temperatures, ocean acidification, and increased storm intensity as a result of climate change.
The vulnerability of small island states to the physical impacts of climate change is exacerbated by a number of socioeconomic stressors: high population growth and high population densities, for example, strain water resources through over-pumping of groundwater, excessive damming, and pollution as well as placing additional stress on food supplies, utilities, infrastructure, coastal settlements and waste disposal facilities. Over-development of coastal infrastructure, including seawalls, groins, and causeways, often results in net erosion by interfering with the natural patterns of sediment flows, despite the fact that these structures are intended to prevent erosion and preserve island structure. Finally, the threat to mangrove forests and coral reefs posed by climate change is exacerbated by coastal development, marine pollution, runoff of sediment and nutrients, overfishing, mining, and dynamiting.
Given the many climate-related challenges facing small island states, their ability to adapt is critical for prosperity in a changing climate. Unfortunately, adaptive capacity is often limited by insufficient technical and institutional capacity as well as by lack of funds. The cost of many adaptation measures, especially “hard” engineering measures, is frequently beyond the means of national governments. Even when such projects can be financed internationally, it can be at risk of diverting development aid from other priorities.
Small island states are uniquely vulnerable to climate change because of their geography and socioeconomic characteristics, and their economies are particularly threatened in the context of those environmental challenges. They serve as an important reminder that climate change is a global problem whose impacts are felt locally. The physical impacts of a changing climate do not exist in a vacuum, disturbing only an isolated segment of an islands’ physical structure. Instead, they alter a complex web of physical, social, and economic characteristics that collectively determine an island’s ability to adapt and thrive in a changing climate.