The claim that a third of the world's animal species have been made extinct is a dead duck.
Following the publication on 10 July 2002 of a report by WWF (no, not the World Wrestling Federation, but the conservation organisation formerly known as the World Wildlife Fund), it was widely reported that more than one in three animal species have been wiped from the face of the Earth since 1970.
‘[H]uman economic activity [has] reduced the number of surviving animal, bird and fish species by 35 percent over the past 30 years’, stated the environmental news service Planet Ark (1). ‘Freshwater fish [have] been especially badly hit, losing over half the species in existence in 1970′, it continued – adding that marine species have declined by nearly 40 percent. The Environmental News Network, Yahoo and even Reuters also presented some or all of these statistics (2).
That’s an awful lot of species to lose in such a short space of time, even in comparison to estimates of the more doom-mongering elements of the environmentalist movement. If we assume (conservatively) that there are 10million species on the planet, then it means that something like 3.5million species have disappeared in the course of a single human generation. That is even more than the 1.2million extinctions that would have occurred over the same period at a rate of 40,000 per year – an oft-cited and highly dubious estimate made by conservationist Norman Myers in 1979 (3). Fortunately, however, the reported figures are wrong.
In fact, the WWF report on which these stories were based – Living Planet 2002 – has little to say about extinction rates at all (4). It is actually concerned with the rates of decline of populations of species, and it finds evidence that, on average, species comprise 37 percent fewer individuals today than in 1970.
The error may be attributable to an ambiguously worded press release put out by WWF about the report (5) – in which case, certain journalists apparently did not seek clarification from the report itself.
But it is not difficult to understand how, once the mistake had been made, such outlandish figures got by so many news editors. News of environmental catastrophe tends to be accepted without question. The idea of plummeting biodiversity has become so ingrained in our mindset that the actual number of species reported to be disappearing per unit time doesn’t matter – just as long as it’s a very big number. Society, it seems, is content only when it can be confident that Mother Nature is drawing her final, wheezing breath.
Of course, though not necessarily a harbinger of imminent environmental carnage, the finding that all the planet’s species have declined by an average of 35 percent is worthy of further attention. But a closer look at the WWF report reveals a gaping chasm between the actual data and the conclusions drawn from them.
The study is based on a sample of 694 species for which long-term population data are available. It cannot be assumed that such a sample is representative of all the world’s species. Indeed, the report’s authors admit that ‘Inevitably, the [sample] is dominated by species which people have an interest in monitoring.’ (6) Which means that the sample is sure to contain a disproportionately large number of species consumed or otherwise utilised by humans, as well as those already receiving attention from conservationists.
It is, therefore, likely to be biased in favour of species that are, by definition, declining. And, if you look at population trends in a sample of organisms that are declining, don’t be surprised if you discover that they are, well, declining.
The authors of the report have not controlled for this highly likely possibility. But this did not stop them applying the rate of decline of their sample to the world as a whole: ‘[S]ince 1970, populations of the world’s forest species declined by some 15 percent, marine species populations by 35 percent and freshwater species populations by a particularly alarming 54 percent.’ (7)
What is worrying here is less the rate of global ecosystem decline, than that unjustified extrapolations from a small, poorly controlled, non-peer-reviewed study can make it into the mainstream press unscrutinised, and become exaggerated beyond recognition along the way.
Perhaps we’d have a better understanding of the state of the planet had the research been conducted not by the conservation organisation formerly known as the World Wildlife Fund, but by the World Wrestling Federation. And Harry Carpenter might have made a better job of reporting on it.
Stuart Blackman is a freelance science journalist.
(1) Living standard seen slumping as resources run out, Planet Ark, 10 July 2002
(2) World seen facing slump as natural resources run out, Environmental News Network, 10 July 2002; World Seen Facing Slump as Natural Resources Run Out, Yahoo, 9 July 2002; Earth may slump as natural resources run out, Reuters, 9 July 2002
(3) The Sinking Ark: A New Look at the Problem of Disappearing Species, Norman Myers, Oxford: Pergamon Press, 1979. The estimate is criticised in The Skeptical Environmentalist, Bjørn Lomborg, Cambridge University Press, 2001, Chapter 23
(4) Living Planet 2002 (.pdf), WWF
(5) Wake-up call for Planet Earth as natural resources decline, WWF-UK, 9 July 2002
(6) Living Planet 2002 (.pdf), p30
(7) Wake-up call for Planet Earth as natural resources decline, WWF-UK, 9 July 2002
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