Pest-free islands that serve as strongholds for some of the world's rarest species could be submerged if sea levels rise as high as climate scientists predict, according to a new study.

Researchers say conservation projects on islands involving pest eradications and translocation of endangered species could be undone because many are low-lying and in danger of being submerged by sea level rises of up to 2.3 metres by 2100.

The study, published in prestigious international journal Trends in Ecology & Evolution, estimates up to 20,000 islands globally could be entirely submerged threatening hundreds of endemic species with extinction.

Of 604 islands where invasive species have been eradicated, 26 are predicted to be completely inundated at a sea level rise of 1m.


"New Zealand has led the world in pest eradications and translocations for decades, but with impending climate change, we will need to shift our focus to conservation programmes on larger islands such as Rakiura [Stewart Island] and Aotea [Great Barrier Island], and the New Zealand mainland," said study co-author Dr James Russell, of the University of Auckland's School of Biological Sciences.

As well as rising sea levels, vulnerable species face a predicted increase in the number and intensity of cyclones, greater tidal ranges - causing more seawater flooding - and changing climatic conditions leading to habitat loss.

Unlike their mainland counterparts, island species had nowhere to go.

"It may be that eventually we will be faced with some tough decisions about whether we move species in order to save them or whether we do nothing and let them go extinct," said Dr Russell, who worked on the study alongside researchers from the University of Paris Sud and Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO).

"But one of the things we need to start thinking about now is which species are most at risk from rising sea levels and the options for saving them."

Climate change and the looming threat from rising sea levels would need to be a key consideration for future island restoration work, and it may be that larger islands at less risk of submersion will have to become a higher priority for invasive species eradication, the study concluded.