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Climate change affects islands, but one snail hangs on.

By Paul Robinson - 09 Sep 2014 9:14:0 GMT
Climate change affects islands, but one snail hangs on.

This small gastropod snail represents the equally small islands now threatened with sea-level rise and climate change. While the continents have areas to which we can remove, if drought or flood affects us, islands have no such "refugia." The consequences of this warming we have brought on ourselves have been felt, are being felt and in future, you can bet we'll all be feeling them; Aldabra image; Credit: © C.Onezia, SIF

Climate change doesn't have such career-threatening effects, if you're a snail!

The whole scenario of extinction for species as the globe warms is correct, but one snail, Rhachistia aldabrae, that was thought extinct in Aldabra, has been found in thick scrub on Malabar. This species was previously abundant, in the 70s, but a change in the ecology has caused its demise, probably associated with rainfall. Young snails were killed off in the extreme hot summers while the adults simply died of old age. This is hardly very good news, but it makes us all feel better, along with the Seychelles Islands Foundation who announced this reincarnation.

The group discovering several juveniles and adults last week in an "expeditionary force" included Junior Skipper Shane Brice along with Senior Ranger Training Officer Catherina Onezia , who took the photographs so expertly. They state on their Facebook page here as Absolutely Amazing News that "the snail is a beauty and a perfect beacon of hope for small islands." This message should reassure some of us that endemic island species can survive, but unfortunately it's the vagaries of changing weather that seem to have rescued this gastropod.

Aldabra is simply a coral atoll, built on an extinct volcano and famous for its giant shells, but they're tortoises. In 1997, the last snail was seen on the UNESO World Heritage Site, as the island's rainfall declined, but whether it has been missed within its ecosystem is uncertain. Every species has its place however, and we can assume that several bird species and many other possible plants and animals such as algae will benefit from its presence. Rachistia is a genus of air-breathing algae-grazers from both East Africa and Asia, so it's impossible to tell from which direction the colonists came to this isolated atoll. In the future, we have little hope that we can avoid a re-extinction because the numbers are very small, the gene pool must be in a classic "bottleneck" and those summers are very hot. As a case study for every species on a distant island, this snail is an excellent example. How can we cope with climate change and avoid losing plants, animals and people from these delicate examples of those areas subject to the first climate change losses.

For the latest information on atmospheric and oceanic links on climate change, we reported on - Calamity in climate change here.