Are our scientific institutions being colonised by activists less interested in pursing objective truth than in spinning a political narrative? It is worth asking given an extraordinary spat which is developing among evolutionary biologists as to whether life on Earth is experiencing a ‘sixth mass extinction’.
The trouble with all these extrapolations is that they are being made from a tiny number of extinctions which have occurred so far
In April a paper by John Wiens of the University of Arizona and published in the journal Trends in Ecology & Evolution argued that while the Earth is ‘on the brink of a major diversity loss’ which would be ‘catastrophic’, there was little evidence to suggest that it will be on the scale of the five mass extinctions which fossil records indicate have occurred during the Earth’s history. While extrapolations from current evidence could possibly support a case for arguing that between 12 and 40 per cent of the world’s species of fauna could be lost, he and his co-authors argued, they do not suggest that the losses would reach 75 per cent of all species – the usual definition of a mass extinction event.
Wiens and his colleagues analysed scientific papers which used the term ‘sixth mass extinction’ and concluded that many don’t present any evidence at all. Others are based on extrapolations such a distance in the future as to be meaningless – one paper suggested that the 75 per cent threshold would be reached in 3.6 million years, by which time many new species will presumably have evolved. Human beings, after all, have only been around for about a million years.
The trouble with all these extrapolations is that they are being made from a tiny number of extinctions which have occurred so far – less than 0.1 per cent of the world’s creatures have gone extinct in the past 500 years. Moreover, Wiens points out, a lot of the extinctions which have occurred so far have involved species whose island habitats have been invaded by outside species. Most of the world’s species live in very different conditions, where they have already been forced to compete with rival species. Simply extrapolating from species which have been lost so far ignores something rather important: that the extinction of one species is often the product of the success of another species – the demise of the former does not spell similar doom for the latter.
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All these points, one might have thought, would be received by other biologists as valuable contributions to scientific debate. But that is not quite how things have turned out. A letter also published in Trends in Ecology & Evolution, authored by Robert Cowie of the University of Hawaii, does not so much argue against the case made by Wiens as try to damn him for daring to question the existence of a sixth extinction in the first place. ‘Arguing that we are not experiencing a Sixth Mass Extinction, or at least playing it down, give support to those who would happily allow it to happen.’ The title on the letter even includes the word ‘denying’. In other words, don’t spoil our narrative – if you do, you will give succour to all those nasty, right wing Trumpians who would love to quote your work to justify their climate-denying assault on Planet Earth.
Wiens, though, can hardly be accused of being a Donald Trump sympathiser. On the President’s first election in 2016 he described the event as a ‘global disaster’. In that same year he wrote a paper in the journal PLOS Biology which suggested that he then thought the Earth was indeed heading for a sixth mass extinction. We are not there yet, he wrote, ‘but I think unfortunately we are on track for that to happen. That’s sort of good news – it hasn’t happened yet. But if we don’t do anything it seems like that’s going to happen in the next 50 to 100 years.’
If he has now had a change of heart on a mass extinction (while still thinking a pretty disastrous species lies ahead) it would seem to be less an ideological position than the result of a simple re-assessment of the evidence. As he writes in his latest paper: ‘continuing to use this phrase risks the credibility of conservation biology and science in general. Similarly, rejecting scientific scrutiny of the sixth mass extinction because of fears regarding media coverage seems particularly inappropriate. Science that cannot be scrutinized is not science at all.’
Quite, but that is evidently not how all people employed as scientists seem to see it. On the contrary, many seem more than happy to lob the emotive word ‘denier’ at anyone with whom they disagree – and not just in the world of climate science.
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