On September 20th 2014, The Times published an article, “Snail ‘wiped out by climate change’ is alive and well.”

It reported the rediscovery of the Aldabran banded snail (Rhachistia aldabrae), which was declared extinct in 2009 by the International Union for the Conservation of Nature (IUCN), after repeated searches in its known habitat found no sign of the snail for over a decade.

In 2007, a scientific paper had pieced together the recent history of the snail population and the climate, and concluded that the snails extinction could be explained by the increasing frequency of dry years, leading to lower survival and reproduction.

But an expedition in August 2014 rediscovered the species in dense mixed scrub of a little-visited part of Aldabra. Conservationists celebrated the rediscovery, while also noting that the species is still extremely rare and its persistence by no means assured.

The Times article developed the story in a completely different direction, using it to challenge the basis for conclusions that the Intergovernmental Panel on Climate Change (IPCC) published earlier this year on species extinctions under climate change.

The Times claims that the Aldabran banded snail was cited in another paper (which I infer to be Cahill et al. 2013), a review of existing evidence, as “the clearest example of man-made climate change causing an extinction”.  It states that this was a major strand of evidence in the IPCC’s conclusions on future extinction risks, which were summarised as: “A large fraction of both terrestrial and freshwater species faces increased extinction risk under projected climate change during and beyond the 21st century”.

As a contributing author to the relevant IPCC chapter on terrestrial and inland water systems, I think it is important to clarify that neither of these assertions is correct.

First, Cahill et al do not list the snails as an example of manmade climate change causing an extinction. In fact, they don’t dwell on the details of any of the 20 species extinctions (out of 800) where IUCN includes climate change as a causal factor, because of the speculative nature of the evidence. They do highlight seven cases of local extinctions where climate change does seem to have played a role. But none of these is a global extinction, and the Aldabran banded snail is not one of the seven.

Secondly, our IPCC chapter reviewed a very large scientific literature and concluded that other pressures, especially habitat loss, overexploitation, pollution or invasive species, are the major causes of recent species extinctions. It is clear up until now these pressures have dominated, and the limited amount of climate change so far experienced has had little measurable impact. While there are a few species where climate change is implicated in local or global extinctions, it is almost always associated with other pressures, which interact and make it difficult to attribute extinction to any one cause.

Overall, the IPCC concludes that there is very low confidence that recent species extinctions can be attributed to climate warming. We cite the Cahill et al review mainly to support the conclusion that there are many other stronger pressures than climate change, and that the attribution evidence is generally very weak. That paper tells us little about future risks.

So the reported extinction of the Aldabran banded snail is not a significant part of the Cahill et al review, which in turn does not constitute a major strand of evidence used by the IPCC for assessing future climate change impacts on the natural world. The Times is wrong on both counts, as a reading of Cahill et al and our IPCC chapter would have quickly shown.

The IPCC concludes that:

“Future species extinctions are a high risk because the consequences of climate change are potentially severe, widespread and irreversible.”

But it also highlights the fact that other pressures are not abating, and that climate change

“…interacts with other stressors, such as habitat modification, over-exploitation, pollution, and invasive species.”

Risks to species from climate change will increase in future. That is a major cause for concern, as is our limited ability to predict which species will be at risk, where and when. The Aldabran banded snail is a recent case study that does little to inform us about these future risks.