Snails in New Zealand sliding to extinction due to climate change

Climate change is a major factor for the near extinction of some of the most spectacular land snails in the world, New Zealand Department of Conservation (DOC) said on Monday.

"Right now, 43 types of carnivorous land snails are classified as nationally critical, the final status before extinction," said DOC Science Advisor Kath Walker.

The latest threat classification report on New Zealand's carnivorous land snails shows that of the 109 species assessed, 48 have declined in status while only six have improved.

The report's expert panel has called for actions to control exotic browsers and predators, protect habitat and address climate change, if many of the giant land snails are to survive.

The carnivorous land snail populations would crash by a further 95 percent over the next few decades, if the high rate of decline continues, said Walker, leader of the report panel.

Wainuia clarki snails have slid from nationally vulnerable to nationally critical due to a rat invasion on its previously secure island habitat on Lake Taupo, while its mainland colonies suffer from predation by thrushes and hedgehogs, and drier forest floor conditions, Walker said.

Te Paki kauri snails have become nationally critical due to predation by rats and pigs, and increasingly severe and frequent summer droughts have made it harder for these moisture-dependent snails to survive and breed successfully, she said, adding 28 taxa of Powelliphanta snails, some of the largest, most brightly colored land snails in the world, have become nationally critical.

Climate change is to be blamed as it is reducing soil moisture in summer, Walker said, adding high numbers of feral pigs, goats, deer, possums and hares are exacerbating climate change problem by drying, removing and degrading the leaf litter that nourishes snail habitat and their earthworm prey.

"A warming climate also means rats are invading some Powelliphanta species' mountain-top homes, which previously were predator-free," she said.