It has been thought that the Pacific nation of Tuvalu was under threat from sea level rise, but it has been found to actually be expanding.

Comprising of 101 islands across nine atolls, research from Auckland University found 73 of the islands are larger than they were 40 years ago.

Researcher Dr Murray Ford from the School of Environment says Tuvalu has seen a net increase in land area of 2.9 percent or 73.5 hectares.

"Tuvalu has been experiencing sea level rise at a rate of over three millimetres per year, and what this shows is that the island's themselves are highly dynamic.

"Primarily, it's driven by the generation of sediment from the reef around it. And that might be from storms breaking up the reef, or just regular biological activity on the coral reef itself."

The researchers say Tuvalu is still likely to be habitable a century from now.