Tuvalu's ambassador to the United Nations, Enele Sopoaga, says more saltwater is getting into the water table, making drinking water brackish.
Mr Sopoaga has told reporters at a UN conference the islands where he visited his aunts as a boy are now gone.
He says the taro roots his family have eaten for generations grow less robustly each year - owing to increased salt water.
Mr Sopoaga says that 25 people were forced to leave after three houses disappeared in the lagoon of his home island, Nukufetau.
He says some atolls have been reduced to uninhabitable patches of sand, devoid of vegetation.
Mr Sopoaga says people have asked him why he hasn't moved his people inland.
He says he responded by telling them there WAS no 'inland'.