In The Lazarus Snail’s Tale, I wrote about the climate change-caused extinction of an island snail, which turned out to be nothing of the sort. Leaving aside that the climate data was thin to the point of non-existent, the main problem with the claim was that the snail was not, in fact, extinct.

Thus another “It was climate change wot dunnit” story went into the bin, or it did for those of us who were paying attention.

I wrote about another such in The Golden Toad’s Tale. (Though this species is, sadly, deceased.)

But to go extinct, you first have to pass through the stage where you are endangered. Your population is sliding downwards, but you still exist; the golden thread holds. After the fact, it matters why the extinction happened, as a lesson. It also matters why a population is sliding down through abundance categories, from scarce to rare to endangered, or distributional ones, widespread to restricted to local – because here there is still time to do something to salvage the situation. Naturally, as a species you can be common, but in a very restricted area, such as an oceanic island. This is no protection against precipitous decline; the overall population is low, and all eggs are in the same basket.

Now, regarding snails on oceanic islands, they are a conservation disaster. What tended to happen in pre-historic times was one or a few colonisation events, and the lucky snail species that arrived on the remote island (probably rafted there by debris, washed down a river from a “nearby” continent) subsequently underwent adaptive radiation, so one colonising species became ten, or more, endemic species.

Next, humans arrive on the scene, and far before carbon dioxide was even a gleam in Al Gore’s eye, we went to work. Not that anything was deliberate at the beginning. Other things were more important, and conservation didn’t even exist. So if we needed wood, we destroyed forests. Goats were released, so that they could breed, and be eaten on a ship’s return years later. Rats came by accident. And so on. By the middle of the twentieth century, a series of snail introductions went on, accidental or deliberate. We had the giant edible snails, and then, when they started throwing their weight around, we had the carnivorous rosy wolfsnail Euglandina rosea, as mentioned in the Lazarus Snail’s Tale. These found the indigenous gastropods more to their liking than the giant rubbery introduced species they had been sent to hunt, and consequently the local species were wiped out by the dozen. (Actually, hundreds of species of land snails on oceanic islands have gone extinct in historical times.)

The Guardian enters the Bermuda Triangle

With that as a primer, today came news of a success story in island snail conservation:

Bermuda snail thought to be extinct now thrives after a decade’s effort

It was a familiar tale of direct human influence, whether intentional or unintentional, and a last-minute reprieve, thanks to strenuous efforts by conservationists. Or was it? Not entirely, not according to the Guardian:

The snails, which are only found in Bermuda, had been hit by global heating and habitat loss, but their decline was accelerated by the introduction of predatory “wolf snails” and carnivorous flatworms, which ate the smaller native species.

(Thank you to Mark for reporting this disgraceful line by our friends, those liars for Gaia, at the Guardian.)

They just couldn’t help themselves, eh? They just had to shoehorn in “global heating,” without which no bad event would ever happen. Now wait a minute, I hear you cry. Just give them a chance. Maybe, this time, they’re right.

Well, they’re not. Euglandina was introduced to Bermuda between 1955 and 1972, by which time those making the introductions ought to have known better. [Even the Guardian might admit that this pre-dates the era of “global heating,” making their statement a nonsense, even if climate had anything to do with anything.] Of the series of introductions, Cowie et al (2026) say:

In the Atlantic, Euglandina, as well as G. quadrilateralis and G. kibweziensis, have only been introduced to Bermuda, from Hawaii between 1958 and 1972. These introductions were intended for control of two other introduced snail species, Rumina decollata, accidentally introduced in the 1870s with imported plants and a facultative snail predator itself, and Otala lactea, introduced initially for food in 1928 but escaped; both became agricultural pests. The intended control by Euglandina in particular was not successful, but the drastic decline of species in the endemic genus Poecilozonites was attributed to it.

Cowie et al, references removed for clarity

[G. quadrilateralis and G. kibweziensis are other predatory snails.]

Of 11 species of Poecilozonites, found nowhere else but Bermuda, only 2 remain. The larger of the two was apparently thought extinct, but was re-found in an old alleyway in 2014. Naturally, the alleyway habitat was destroyed for development, but snails were collected and a breeding programme begun, at the Zoological Society of London, and Chester Zoo. The smaller species was collected earlier, and was “extinct in the wild”.

Here (page 9) you can read about the breeding and release of Poecilozonites. A journal (all right, a newsletter) called Tentacle has got to be worth a read, right?

The larger species has been released on islets around Bermuda, that are free of Euglandina and chums: Nonsuch Island, Hall’s Island, Trunk Island, Nelly’s Island and Saltus Island. (As well as two sites on the main island). The smaller species has been released on Nonsuch, but in a more controlled way, with protective enclosures. The idea, I’m sure, is to have populations on as many safe islets as possible. But the total area occupied is measured in hectares, rather than square kilometres. I suppose the thought has not occurred to the Guardian that, if “global heating” really is the problem, then there is not much point starting new populations… in exactly the same place.

Finally, the IUCN Red Listing for the larger snail makes no mention of climate change, or even “global heating.” Note that the assessment pre-dates the reintroductions, being dated to 2019. Note also that while the IUCN used to scrupulously avoid blaming climate change for anything, they have let their standards slip recently; nevertheless, they do not blame climate change for this snail’s problems.

The only known extant subpopulation of this species occurs on Port’s Island, where its continued presence is threatened by accidental introduction of invertebrate predators, mainly Euglandina rosea and terrestrial flatworms (e.g., Bipalium vagum). These predators are believed to be the reason for the demise of the species from the larger islands of Bermuda and could relatively rapidly spread throughout the small (7.6 ha) Port’s Island.

IUCN Redlist

Please, Guardian, rediscover your principles.

/message ends

PS. Poecilozonites was the subject of Stephen Jay Gould’s doctoral thesis.

PPS. The featured image is from Gould’s research on Poecilozonites. It’s the larger of the two extant species.