o In 2011 UNEP The United Nations Environment Program recently released a report on 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.
CLIMATE EMERGENCY INSTITUTE
The Health and Human Rights Approach to Climate Change
IPCC 2014 AR5 chapter on Small Islands
Current and future climate-related drivers of risk for small islands during the 21st century include sea level rise (SLR), tropical and extratropical cyclones, increasing air and sea surface temperatures, and changing rainfall patterns (high confidence; robust evidence, high agreement).
Current impacts associated with these changes confirm findings reported on small islands from the Fourth Assessment Report (AR4) and previous IPCC assessments. The future risks associated with these drivers
include loss of adaptive capacity and ecosystem services critical to lives and livelihoods in small islands.
SLR poses one of the most widely recognized climate change threats to low-lying coastal areas on islands and atolls (high confidence; robust evidence, high agreement). It is virtually certain that global mean SLR rates are accelerating.
Projected increases to the year 2100 superimposed on extreme sea level events (e.g., swell waves, storm surges, El Niño-Southern Oscillation) present severe sea flood and erosion risks for low-lying coastal areas and atoll islands. Likewise, there is high confidence that wave over-wash of seawater will degrade fresh groundwater resources and that sea surface temperature rise will result in increased coral bleaching and reef degradation. Given the dependence of island communities on coral reef ecosystems for a range of services including coastal protection, subsistence fisheries, and tourism, there is high confidence that coral reef ecosystem degradation will negatively impact island communities and livelihoods.
Given the inherent physical characteristics of small islands, the AR5 reconfirms the high level of vulnerability of small islands to multiple stressors, both climate and non-climate (high confidence; robust evidence, high agreement).
There is increasing recognition of the risks to small islands from climate-related processes originating well beyond the borders of an individual nation or island. Such transboundary processes already have a negative impact on small islands (high confidence; robust evidence). These include air-borne dust from the Sahara and Asia, distant-source ocean swells from mid to high latitudes, invasive plant and animal species, and the spread of aquatic pathogens. For island communities the risks associated with existing and future invasive species and human health challenges are projected to increase in a changing climate.
The IPCC suggests adaptation benefits small islands to the extent of reducing risks, even with global warming as high as 4C. This is contyradicted by the projections and multiple devastating impacts and practically impossible at above a 1.5C global warming over the long term, as the Small Island States has complained of for many years.
Small Island States
Vanuato feature 2013 CSIRO Commonwealth Scientific and Industrial Research Organisation
Current and future climate of Vanuatu