Wednesday, February 25, 2015

The American Signal Crayfish – a parable for our times

White Claw Crayfish
In the UK we have a neat little crayfish called the White Claw Crayfish (though its claw doesn't look very white in this picture). It’s smaller than its American cousin, the Signal Crayfish, and was widely dispersed around the UK as recently as 2002. But things have changed.

On a recent episode of the BBCs Winterwatch, Chris Packham visited a stream in Devon that is now not only devoid of our native crayfish, but is devoid of anything other than the Signal. In the example we saw in Devon, they have eaten everything out of one stream so that the only recourse left to them is cannibalism.

So what happened?

The American Signal crayfish was brought over to the UK for the restaurant trade – some were let loose (perhaps to build up a local stock for consumption) and being the adaptable creature that it is, it didn’t take long for this small crustacean to take over new territories, including most of the UK and a lot of Europe (read this paper for more technical descriptions of how the crayfish spread and are welcome, and unwelcome, across Europe).

Signal Crayfish
The fact that the crayfish adapted well to our environment is no surprise, we already had our own crayfish, so the habitat was ideal. What wasn’t known when crayfish were introduced in Europe is that they carried a ‘crayfish plague’. Not only are their voracious appetites causing our indigenous crayfish to decline, they are also infecting them with a deadly disease.

We can eat crayfish, in fact eating the Signal is positively encouraged on some websites. But you need a licence, because our White Claw is now an endangered species.  The estimate is that it has declined by around 95% since the 1970s. That may seem like a long period, but follow the projections through and our native crayfish is likely to be extinct in a few decades, if not sooner.

So we have the introduced species who were quite happy and thriving in their own environment (the USA).  They have arrived in new lovely habitats with virtually no predators and an abundant food source. And they are devastating the habitat with no thought to their future (of course, they are base animals, they cannot think ahead), and destroying the other living creatures around them. Where there are limited resources, their long term future is rather dubious.

I work in conservation – in an organisation who specialise in wildlife trade monitoring. I see rhinos poached to the brink of extinction, I see wild plants being harvested so that seeking natural medicines in a forest that may have taken a villager a day, now takes a week. I have seen forests destroyed (by legal and illegal logging) and palm oil planted, displacing orang-utans and other native forest dwellers. I see a growing human population: if everyone consumed food at the rate (and volume of meat) that we do in the West, it would take several planet earths to feed us all.  The species that turns from symbiotic to parasitic has a limited future, unless we can change. Unlike the crayfish, we can see into the future – and at the moment, I’m not so sure that we won’t suffer the same fate as the cannibalistic Devon invaders.

Photo credits:
Signal Crayfish: Open University
White Claw Crayfish: BBC Wales

Further reading:
From this blog:
From the web:


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