Researchers say climate change could smash freshwater supplies for island nations.

A new US study examining 43 small island states found the majority of naturally occurring freshwater is groundwater, which is primarily recharged by precipitation.

Recharge rates are therefore likely to be impacted by climate change.

Freshwater resources on small islands are particularly vulnerable to climate change because they are limited in size and easily compromised.

The team used aquifer system characteristics and water-use data for 43 small island developing states distributed worldwide, based on local expert knowledge, publications and regional data sets.

Their vulnerability was assessed by evaluating the recharge volume per capita. For future vulnerability, climate change projections were used to estimate changes in aquifer recharge.

“We find that 44 per cent of islands are in a state of water stress, and while recharge is projected to increase by as much as 117 per cent on 12 islands situated in the western Pacific and Indian Ocean, recharge is projected to decrease by up to 58 per cent on the remaining 31 islands,” the researchers said in a statement.

“Of great concern is the lack of enacted groundwater protection legislation for many of the small island developing states identified as highly vulnerable to current and future conditions.

“Recharge indicators, shown alongside the state of legal groundwater protections, provide a global picture of groundwater supply vulnerability under current and future climate change conditions.”

The full study is accessible here.