Climate Change and Small Islands

Small, low-lying islands are particularly vulnerable to global climate change and sea level rise with the principal impacts falling into three main categories: shoreline erosion, inundation and flooding, and saline water intrusion into surficial freshwater aquifers. Fresh groundwater on small islands occurs primarily as freshwater lenses, floating atop saline groundwater, whose natural size depends on island area, shape, and topography, aquifer properties (transmissivity), and rainfall. Freshwater lenses are limited resources that are vulnerable to salinization from over exploitation and from storm overwash. The sustainability of freshwater lenses depends on maintaining a balance between recharge, captured discharge, and pumping. Decreases in recharge during drought periods can result is a profound shrinkage of freshwater lenses. Anthropogenic activities can impact freshwater lenses through induced changes in recharge rates caused by increased impervious covers. Management of freshwater lenses can be improved through improved well and wellfield design, monitoring of aquifer water levels and salinity, controls on groundwater pumping, implementation of land use practices to reduce the risk of anthropogenic contamination, and managed aquifer recharge.