Reliable access to freshwater is one of the fundamental pillars on which society is built. It is a necessary prerequisite for ensuring food security and a functioning system of public health. For small island developing states, securing adequate freshwater supplies for drinking, sanitation and agriculture is a constant challenge, and climate change is only making it more difficult.
Rainfall is the primary source of freshwater for most islands. While seemingly plentiful in some regions, rainfall is not as dependable a source of water as, for example, land-based glaciers, something that low-lying and low-
latitude islands lack. Instead, SIDS must rely on surface water and groundwater supplies, which themselves are recharged by rainfall. However, these sources are threatened by climate change in a number of ways.
First, shifts in rainfall patterns are expected to increase the frequency and intensity of droughts in some regions. A single prolonged drought can have disastrous consequences on pluvial agriculture and can lead to the rapid depletion of an island's surface and groundwater resources. Second, rising sea level is leading to saltwater intrusion into the groundwater supply. This is an especially serious problem for atoll islands, which are permeable and prone to flooding from within. Saltwater intrusion has already forced some islands to switch from traditional subsistence crops to more salt-tolerant varieties. Additionally, higher air temperatures lead to higher rates of water evaporation, reducing soil moisture and decreasing the rate of groundwater recharge.
There are few good options available to SIDS. Desalinization is energy intensive and expensive. Importing freshwater to remote islands is also expensive and not practicable for supporting any meaningful agricultural activity. Building new freshwater storage facilities can help to extend supplies to a certain extent; but even they would likely prove inadequate in the face of a severe drought.
An important problem already affecting numerous coastal areas, including small islands, is saltwater infiltration in soils or salinization, especially in atoll countries such as Tuvalu, the Maldives or Kiribati. Atolls get their freshwater supplies from rainfall or groundwater (rainfall filtered in the ground). Freshwater is lighter than saltwater; a lens is formed under the atoll with freshwater on top. This reserve of freshwater is vulnerable to a decrease in rainfall (as the lens cannot replenish) and over-drilling, which can contaminate the lens water with brackish water.
As projections from the IPCC have shown, there is strong evidence that water resources and distribution of rainfall on small islands will be compromised with climate change. In Kiribati, for instance, a 10 per cent reduction in average rainfall by 2050 would lead to a 20 per cent reduction in the size of the freshwater lens. In addition, increased frequency of extreme weather events, sea-level rise and resulting land loss are likely to increase the stress on freshwater lens on atolls. For example, studies in Tarawa, Kiribati, demonstrated that a 50cm rise in sea level accompanied by a reduction in rainfall of 25 per cent would reduce the freshwater lens by 65 per cent.
These negative impacts of climate change cumulated with population increase and put the availability of freshwater resources at risk. Water quality is likely to be degraded by saltwater infiltration. This could lead to health problems related to the scarcity of freshwater and to the spread of water-borne diseases. As freshwater becomes scarce, life on islands, in general, will be more difficult to sustain. The inhabitants of the Carteret Islands in Papua New Guinea are currently suffering increased water shortage and rely on coconut water since average precipitation has decreased and their freshwater supplies have been contaminated by saltwater infiltration.
Saltwater infiltration also has severe adverse impacts upon agricultural practices. As saltwater infiltrates the aquifers and soils, many salt-intolerant traditional crops, such as taro or pulaka, die from salt contamination, which affects the traditional diet of islanders. For example, across the Pacific, taro crop is a fundamental element of islanders' diet. Because of salt contamination in soils, many island communities have been forced to relocate their plantations further inland or in higher grounds. For atolls, which culminate at less than 5m above sea level, the situation is even more precarious: some island communities (e.g. in Tuvalu) have started growing traditional crops in tin cans since they are unable to relocate to higher grounds. Other communities are switching to salt-resistant crops. However, these are expensive or difficult to obtain. Indeed, some require genetic modification to adapt to saline soils (e.g. tomato and rice), or others are not part of the traditional diet of the islanders. The implantation of such crops is, thus, modifying the diet and culture of islanders around the world.
Similarly, the import of foreign goods/foods (such as rice) to palliate the scarcity of locally grown goods from increased soil salinity has not erased all problems. Islands are often removed from major centres. As a result, these imported foods are often expensive and take time to be shipped to these islands. Therefore, the risk of food scarcity is a threat that constantly looms over island communities.
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