Water vole of old rubbish

Browsing the web today, I was reminded of what was the possibly worst example in 2009 of PR masquerading as a wildlife news story.

In November the BBC reported that a survey of the UKs canals had shown that 2009 had been a ‘bumper year’ for water voles. You might remember the story as it was quite widely reported, being covered in:

The Guardian

The Independent

The Telegraph



Mail Online

Good news apparently, and something that interested me. So I naturally looked at the source: the British Waterways Wetland Wildlife Survey.

Members of the public were invited to send in their sightings of wildlife on canals.

The public had done something similar in 2008 as well.

You can see the results here but as they don’t take up much space I’ve reproduced them in full below.

The results of the 2008 and 2009 British Waterways National Wildlife Survey

It was the remarks at the end of the piece on the BBC’s November 2009 article that caught my eye.

In 2009 the survey went web-based and there were ‘a lot more entries [in 2009] than in the previous years‘ according to a British Waterways spokesperson.

And the total number of records went up from ‘6000-7000’ a year to ‘42,000’.

It was at this point I began to smell a rat – well, more specifically a water rat.

In 2008 there were 43 records of water voles. In 2009 there were 89 sightings of water voles. This was what the BBC and other reported as a ‘bumper year’ for water voles.

But hold on a moment: the total number of observations increased by about 6 times – from somewhere between 6 and 7 thousand to 42,000, presumably because more people sent results in – not because wildlife suddenly increased 6 fold on the canals. (Nobody would seriously suggest that there had been a near 20 fold increase in mallard between the two years – take a look at the real data here collected by the British Trust for Ornithology which shows a long-term increase in breeding mallard with number fairly stable since 2000).

If you take that increase in recording effort roughly into account – by multiplying the 2008 count of water voles by six – you see that if you’d applied the 2009 amount of survey effort in 2008 there should have been around 250 water voles recorded.

So, far from being a bumper year, if anything the survey suggests that water voles might have declined. Of course, the truth is that the survey is so silly that it’s not really worth any attention at all.

The story, and the survey itself, is just a bit of nonsense – but it is a PR triumph.

Does it matter – well, probably not much. It’s just one flawed piece of work – a little floating thing in the otherwise fairly clean stream of information. Harmless you might say, except next time when you hear a more balanced story about the state of water vole populations, which one will you believe? I can’t help feeling that this kind of thing feeds the mistrust people have of statistics, and if we want to protect the world that does matter.


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