Did I ever tell you how exciting snails are?

DSC_4024 Did I ever tell you how exciting snails are? No, wait, don’t go away… Oh well. Now the rest of you have settled down, I’ll continue. My pic, incidentally, shows some Sphacterian snails I met in Greece this summer, which exhibited this odd clustering behaviour I’ve not seen before. But that’s nothing to do with this post.

I was reading the Times, as one does in Waitrose cafe when one can’t find the Torygraph, and came across an interesting article which is paywalled, so in revenge I won’t point you at it. Extinct snail re-discovered at Aldabra Atoll will do instead, and its rather more neutral, which is nice (re-reading: neutral? Maybe, but there’s definitely drivel in there, such as SIF CEO Dr Frauke Fleischer-Dogley said of the re-discovery, “Despite major global environmental threats like climate change, this discovery shows that investments into protecting unique island biodiversity are well-placed”. The substance is:

The Aldabra banded snail (Rhachistia aldabrae), declared extinct in 2007, has been re-discovered alive and well at the UNESCO World Heritage Site of Aldabra Atoll, Seychelles. Before the discovery, the last living individual of the species, which only occurs on Aldabra, was recorded in 1997. Subsequent searches yielded only shell remains. The snail’s apparent demise was linked to declining rainfall on Aldabra and was widely publicised internationally as one of the first casualties of climate change impacts.

I’m a little dubious about The snail’s apparent demise was linked to declining rainfall on Aldabra and was widely publicised internationally cos I remember none of it, but it may be true[*]. It made Biol. Lett. 2007 Short-term climate change and the extinction of the snail Rhachistia aldabrae (Gastropoda: Pulmonata) as published by the Royal Society.

[*] Actually, lets examine this a bit more. Forbes (link below) who are no friends to GW say A 2012 article by Abigail Cahill and Matthew Aiello-Lammens and colleagues in Procedings of the Royal Society B cited it as one of just a handful of cases where climate change is thought to be the immediate cause of extinction.The UN’s Intergovernmental Panel on Climate Change referred to the Cahill study… which I interpret as trying to show how widely used this example was. But note that the IPCC (WG II) didn’t actually refer to the Gerlach paper at all; only to the Cahill overview (for some reason the IPCC call it Cahill 2013, even though it looks to be 2012; odd [But see comment #4]). And what the IPCC has to say from Cahill is quite nuanced:

At the opposite end of the spectrum, species extinctions are very difficult to attribute to climate change (Section, in part because other factors dominate recent extinctions. This does not mean that climate has not played an important contributing role; indeed it has been argued that the low level of confidence in attribution is due to the lack of studies looking for climate signals in extinctions (Cahill et al. 2013)

As you’d expect, the obvious suspects made the obvious hay over this. And the Light Side largely ignored it. But should we? As well as a chance to show “balance” this is also a chance to ride one of my once-favourite hobbyhorses, so I’ll take the chance. And the equine is: if you want to know if global warming is occurring, look at the temperature record over a climatologically meaning period. Or, something tied very strongly to it, like sea level or ocean heat content. Other stuff – weather extremes, and in particular extinctions, aren’t good markers because they’re inherently statistically less stable (and for extinctions in most places you have to worry about habitat loss as a cause, too; that’s usually anthro as well, of course, but its not GW). Promoting them to gee up the troops because they’re sexier and more exciting than just-a-few-degrees-warming isn’t a good idea. I really have said this kind of thing before; I’m not making it up. Mind you, it wasn’t popular with the folks then; I doubt it will be now.

Continuing, it seems – in retrospect, though I defend myself from failing to think this at the time on the grounds that I paid no attention at the time – fairly obvious that trying to work out if this particular snail was extinct or not was pretty tricky, of itself. Because, as Clive Hambler says The vast majority of the habitat is virtually inaccessible and has never been visited. It is unwise to declare this species extinct after a gap in known records of ten years. We predict rediscovery when resources permit (warning! Link is to ideologically offensive site, “Forbes”). And just for good measure there’s the usual rather regrettable problem of a journal refusing to publish corrections.

This is a good place to link to Eli’s “words” on the views of government.


* Retraction Watch: At a snail’s pace: Species rediscovered, but paper on its disappearance remains.
* Strangest thing you can see in Ulm

12 thoughts on “Did I ever tell you how exciting snails are?”

  1. “for some reason the IPCC call it Cahill 2013, even though it looks to be 2012; odd”

    It looks to be a cite-checking mistake. When I was working in law I used to double check citations. Nothing infuriates the senior partners more than getting a cite wrong. It is easy to get the cites right, but just because is easy it does not mean you do it without due care.

    “Promoting them to gee up the troops because they’re sexier and more exciting than just-a-few-degrees-warming isn’t a good idea.”

    Bringing up extinctions does get people out of their seats, but it is too often brought up as a current problem when it is more a future problem. Enviro’s try to walk the line on this one, with varying degree of success. I have a few times on the enviro site Grist brought up that we need to get the facts right. There will be plenty of people to shout far and wide if we do not.


  2. What part of “Proc. R. Soc. B 7 January 2013” is so hard to understand?

    [You’re right. I searched that page visually for 2013 and failed to find it; but “Published online before print 17 October 2012 doi: 10.1098/rspb.2012.1890 Proc. R. Soc. B 7 January 2013 vol. 280 no. 1750 20121890” it is indeed. So IPCC are correct, as you’d expect -W]


  3. In all fairness, Gerlach (2007) doesn’t mention temperature as a factor at all. He links it to rainfall.

    [Well yes. But he definitely links it to climate change. Linking the *extinction* to climate change is definitely wrong. It might have been correct to link a restriction of range to climate change; that’s less noisy. But less sexy, too -W]

    And to add more fairness, Cahill et al mentions the Gerlach study just once, in the context of *global* extinctions that are possibly linked to climate change, in a supplementary table.

    Molehill, meet mountain.


  4. Well, he linked climate change to extinction because there were no more observations and all other factors he could imagine simply didn’t work well in the face of the evidence.

    He did not have any evidence of a “restriction of range” either. It turns out to be the case, but in hindsight we always know better (one hopes…).


  5. It’s easy to find reasons to be worried about t’environment, such as the WWF announcement that we’ve lost half our vertebrates (in number) since the 1970’s. GW as a force multiplier is a reasonable argument to make for difficulties Nature is facing, but as ever the context must the be whole package. The small section on ’emergent properties arising from’ in the AR5 (WG3?) is interesting and disconcerting.


  6. Fergus, the Living Planet Index/Report didn’t say ‘we’ve lost half our vertebrates (in number) since the 1970s’. Here’s a useful explainer from an unlikely source (plugged by the ZLS on Twitter earlier today, so if not yer actual horse’s mouth, it’s yer actual horse’s bridle; or something):


    The average vertebrate species is estimated to have lost half of its individuals, not agglomerated vertebrate individuals are down by a half.

    The latter trend would be interesting to know (if not very useful), as would a wild vertebrate biomass trend, but that’s not what ZLS/WWF supplied.


  7. Speaking of the LPI, much has been made of its finding that climate change is one of several current/future threats or the major current/future threat or the sole current/future threat for 7.1% of the vertebrate species it studied or of those species it studied that showed a decline in population since 1970, or something.

    Which variant is it, exactly? The usual suspects didn’t care. 7.1% of all wildlife has been killed by climate change.

    The Living Planet Report says very little about this much-plugged finding – a brief word about caribou, tropical frogs and polar bears and a vaguely worded suggestion that the 7.1% had come from compiling the top three threats suggested by the providers of the time series for the populations of various species. The ZSL, WWF and Living Plant Index websites provide no further info.

    Hoping to clear this up, I signed up for access to the LPI database.

    Not much help there, either. Threats aren’t listed for each species. All you get is brief classification and biome info, some population estimates and the source(s) for the estimates.*

    So: does anyone know what the 7.1% actually means?


    *The first** species I looked at was Atelopus varius, a Costa Rican tropical frog that was supposed to have been driven to extinction by climate change. The sole ‘time series’ source is from 2005 and it gives two population estimates. The second (from 2002, IIRC*) is zero. Hence the extinction. Last year, however, that frog and four of its climate-challenged Costa Rican chums were rediscovered. A fifth chum, the famous Golden Toad, remains extinct – but attributing its fate to climate change has been out of fashion for several years now. Ditto the decline, if not extinction, of its back-from-the-dead chums. Which leaves caribou and polar bears – and the caribou attribution is similarly out of fashion. Which leaves polar bears. Which I’ll give them.

    **And last. The website has been unreachable since fifteen minutes after I logged on. I was on there long enough to find out that none of the supposed supporting documents was available. A shambles. Don’t bother signing up.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: