RNZ reports most of these islands are dependent on ground water that is replenished by rainfall.
Researchers from Simon Fraser University in British Columbia, as part of a UNESCO study, looked at the state of ground water in 43 small island states in the Pacific and the Indian Oceans.
Their study has now been published in Nature Climate Change and author, Diana Allen, said when they looked at the ability of aquifers to recharge they found many small islands in a state of water stress.
She put this down to warmer temperatures causing higher evaporation.
