o The United Nations Environment Program recently released an assessment of the vulnerability of freshwater resources in Pacific Island Countries. While climate change was not the overall focus of the assessment, the authors note that many small Pacific islands are particularly vulnerable to water scarcity due to climate change. Aside from the risk of flooding due to sea level rise, islands are vulnerable because of their hydrology.
Typically, small islands have several layers of groundwater, the lowest level of which is salty. A lens of fresh groundwater floats on top of the salty groundwater, with a brackish transition layer at the boundary between the two. Where the transition between fresh and salty groundwater occurs depends on how thick the fresh water is, because the weight of the fresh water pushes the salt water down somewhat. During droughts, not only does the top of the water table fall, as happens on larger landmasses, but with less fresh water to push it down, the salty layer rises. Since the salt layer is also rising due to sea level rise from climate change, the prospect of wells becoming salty during droughts is becoming more likely. Since during a drought is when these islands typically depend on groundwater, the increased possibility of wells becoming salty is quite serious.
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The Health and Human Rights Approach to Climate Change