Letters to the Guardian telling us we’re doomed are a dime a dozen, but this one is signed by some big names like Noam Chomsky, Rowan Williams, and Professor Grayling, Master of the New College of the Humanities, London. OK, it’s also signed by Caroline Lucas, Naomi Klein, Jonathon Porritt, and Dr Rupert Read, the Socrates of Norwich, but the first named three are not people you would normally think of as thick as planks. Not the kind of people you’d expect to sign any old bit of paper without checking the small print. Well they are and they have.

The letter starts:

In our complex, interdependent global ecosystem, life is dying, with species extinction accelerating. The climate crisis is worsening much faster than previously predicted. Every single day 200 species are becoming extinct. This desperate situation can’t continue.

And continues:

Political leaders worldwide are failing.. corporate capitalism… global catastrophe.. Complacency… paralysis… grave responsibility… climate-emergency… impoverished nations… unsustainable economic growth… planet-plundering imperialism… extreme weather.. emergency investment in agro-ecological extreme-weather-resistant food production… urgent summit…

and ends:

We further call on concerned global citizens to rise up and organise against current complacency in their particular contexts, including indigenous people’s rights advocacy, decolonisation and reparatory justice – so joining the global movement that’s now rebelling against extinction (eg Extinction Rebellion in the UK) … Every one of us, especially in the materially privileged world, must commit to accepting the need to live more lightly, consume far less, and to not only uphold human rights but also our stewardship responsibilities to the planet.

Among the 53 signatories from Britain, I counted nine psychotherapists and the like, and ten representatives of African organisations (for some reason spelt the German way – “Afrikan”) in Britain. There’s also a professor who holds a Leadership Chair in Contentious Politics, the director of Virtual Migrants, Mr Ghosthorse of the Lakota nation, and the King of Djougou.

You’ll note that the emphasis of the letter is on biodiversity and species loss, and there is just one “fact” in the entire eight paragraphs, to whit, “Every single day 200 species are becoming extinct.” So I looked up “200 species extinct” to see where this fact came from.

First stop, the WWF biodiversity page, which says:

How many species are we losing? Well… this is the million dollar question. And one that’s very hard to answer. Firstly, we don’t know exactly what’s out there. It’s a big complex world and we discover new species to science all the time.

Of course, they space it out better than that on the page.

In different typefaces.

For their Readers.

Who haven’t read a book to the end since The Very Hungry Caterpillar..

So, if we don’t know how much there is to begin with, we don’t know exactly how much we’re losing. But we do have lots of facts and figures that seem to indicate that the news isn’t good. If there are: -100,000,000 different species on Earth – and the extinction rate is just 0.01%/year – at least 10,000 species go extinct every year Just to illustrate the degree of biodiversity loss we’re facing, let’s take you through one scientific analysis… The rapid loss of species we are seeing today is estimated by experts to be between 1,000 and 10,000 times higher than the natural extinction rate .

These experts calculate that between 0.01 and 0.1% of all species will become extinct each year.

If the low estimate of the number of species out there is true – i.e. that there are around 2 million different species on our planet** – then that means between 200 and 2,000 extinctions occur every year.

But if the upper estimate of species numbers is true – that there are 100 million different species co-existing with us on our planet – then between 10,000 and 100,000 species are becoming extinct each year. ** Between 1.4 and 1.8 million species have already been scientifically identified.

Well, yes. If you play around with two quantities known to the nearest magnitude, and a third known to the nearest two magnitudes, you’re going to get some pretty impressive numbers. So the number of species disappearing might indeed be 200 a year, or 200 a day, or 200 a minute, whatever.

Of the figures used, the estimates of the natural extinction rate come from fossil studies, I think. I once found one that estimate the rate of loss of species now by looking at the rate of loss of mollusc genera 60 million years ago. The estimate of species loss of “1,000 and 10,000 times higher than the natural extinction rate” comes from a throwaway remark in a book by E.O. Wilson written in the 1970s, when the world was cooling. It wasn’t based on anything, he just made it up. You can do that when you’re a famous biologist. E.O. Wilson was ten years old when he wrote it, or maybe a hundred. Please don’t ask me for exact references. I mean, who cares about details?

The “200 a day” figure may come from a 2010 UNEP report. From the Huffington Post:

According to the UN Environment Programme, the Earth is in the midst of a mass extinction of life. Scientists estimate that 150-200 species of plant, insect, bird and mammal become extinct every 24 hours. This is nearly 1,000 times the “natural” or “background” rate…

So if UNEP gets 200 extinctions a day using E.O. Wilson’s lower estimate of one thousand times the background rate, just imagine what they could do if they took his higher rate? Especially if, like the WWF, they rounded up the known number of species (1.4 to 1.8 million) to a tidy hundred million.

So how many species are actually going extinct? According to the International Union for the Conservation of Nature (IUCN) about 15 since 1950. Not quite the 200 a day claimed by Professors Chomsky and Grayling then.

In other contexts these professors can be quite fussy about figures. I remember Professor Chomsky taking someone to task for repeating the unverified claim that Pol Pot killed 2 million Cambodians. (Professor Chomsky thinks the true figure is several hundred thousand less.) And Professor Grayling gets quite shirty if you claim that a majority of the population voted for Brexit. When you add in the people that didn’t vote, and those who couldn’t vote but who Professor Grayling thinks should have been allowed to (under 18s, the unborn etc.) the true number voting for Brexit goes down from 12 million to about twenty three (WWF figures.)

Are they like this in ordinary life, do you think?