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1 April 2004Printer-friendly versionEmail a friend

Biodiversity: don't get in a flap
The decline of British butterflies does not put us on the brink of a manmade mass extinction.

by Tony Gilland

The prestigious journal Science recently published a paper that, as the press release put it, bolstered 'the "Sixth Extinction" hypothesis' - the notion that 'the biological world is approaching the sixth major extinction event in its history' (1). This is a pretty startling claim - and the UK media reacted in kind, emphasising that this would be the first mass extinction to be caused by the activities of humans.

The paper provided a statistical analysis of the comparative fortunes of British butterfly, bird and plant populations over the past 40 years. The central finding was that the 58 British butterfly species they studied had fared significantly worse than birds or plants. Focusing on this, the authors tentatively conclude that, if insects globally were as sensitive to contemporary environmental changes (in other words, those driven by human activity) as these butterflies, the findings would lend strength to the Sixth Extinction hypothesis.

But can so much really rest on the fortunes of 58 species of butterfly breeding in Britain?

Globally, over one million species of insect have been classified to date, and there are thought to be several million more remaining to be discovered. The geographical and climatic conditions found in Britain are clearly very different from those found in many other parts of the world.

When I spoke to the paper's lead author, Jeremy Thomas, from the Natural Environment Research Council's Centre for Ecology and Hydrology, he freely admitted that 'to go from UK butterflies to world insects is a massive extrapolation', and stated that while the authors of the paper 'are confident about the UK data, the rest is speculation'. It is worth asking why, then, so much attention has been paid to the speculation.

The substance of the paper is a statistical comparison of data collected by volunteers over the past 40 years on the presence of bird, butterfly and plant species native to Britain, in 2861 ten-kilometre-square (km2) grids of England, Wales and Scotland. Some 15million records were collected in six separate surveys by more than 20,000 volunteer recorders. They are the most comprehensive data sets in the world of the changing status for each taxon (birds, butterflies and plants).

The scale of the research helps to explain the interest in the data. But it also emphasises how little is actually known about the changing fortunes of many species that inhabit vast swathes of the planet.

The key finding of the paper, and something that surprised the authors, is that, butterflies, in general, have declined more significantly than birds and plants in terms of their range - the number of 10km2 grids each native species has been recorded in. The authors found that 28 per cent of native plant species (from a total of 1253 species) have decreased in Britain over the past 40 years, 54 per cent of native bird species (from a total of 201 species) decreased over 20 years, and 71 percent of butterfly species (from a total of 58 species) declined over a 20-year period. Two butterfly species have been declared extinct.

Of course, behind the general statistics there is a lot more detail. For example, if you were to look at the data behind the general statistic for birds, you would find that for 84 of the 201 species there has been little substantial change in their range (plus or minus 10 per cent), and that 41 species have increased in range by more than 25 per cent, compared to 25 species that have declined in range by more than 25 per cent. So what is the significance of this high-level statistical analysis?

Jeremy Thomas told me that the wider interpretation of the paper's findings was important because other studies had previously suggested that insects, which make up 54 per cent of the 1.75million species described to date, might be adjusting better to environmental change than their better recorded, but declining, counterparts in the bird and mammal kingdoms. At least for British butterflies, the authors of this paper appear to have shown that this is not the case.

However, Thomas also told me that there had been much debate between the nine authors of the paper about the interpretation of their findings - some being more cautious and others more bold. The broader conclusion they agreed upon for the published paper was therefore carefully worded and cautious in tone:

'If insects elsewhere are similarly sensitive, we tentatively agree with the suggestion that the known global extinction rates of vertebrate and plant species may have an unrecorded parallel among the insects, strengthening the hypothesis, derived from plant, vertebrate, and certain mollusc declines, that the biological world is approaching the sixth major extinction event in history.'

UK governments have promoted the importance of biodiversity in every corner of the country
The 'if' in question does look to be pretty big. Surely this should prompt further debate and research among the world's biologists, before any significant conclusions are reached?

Thomas agreed that the paper should be a starting point for scientific debate. But he also warned that 'if you are advising policy makers you usually can't wait until you have the decimal points in place but have to go on the best available information even if it is tiny. Otherwise there is a danger that it will be too late to do anything'.

If nobody but botanists and biologists cared about the fate of Britain's butterflies and plants, there might be more merit to such a headline-grabbing approach. But given that there is an official obsession with biodiversity in the UK - and, indeed, a reluctance to believe anything but scare stories - this latest extinction hypothesis seems rather unnecessary and unhelpful.

Politicians and policymakers have been quick to grab hold of the biodiversity agenda. First coined in the late 1980s, the concept of biodiversity was quickly turned into an international environmental problem, gaining formal recognition through the UN's Biodiversity Convention signed by 150 countries at the Rio Earth Summit in 1992.

Since then, successive UK governments have led the way in promoting the importance of biodiversity in every corner of the country, from farmland to city centres. The UK government's 'Biodiversity Action Plan' tells us that 'Biodiversity encompasses the whole variety of life on Earth. It is not restricted to rare or endangered species but includes the whole of the natural world from the commonplace to the critically endangered' (2).

This broader context indicates why research linked to biodiversity tends to gain such a wide airing in today's media - particularly when its findings are negative. This is less about the scientific findings, and what these tell us about real changes in the natural environment, than with the fact that they press the right buttons - tapping into a heightened concern about nature and an intense negativity about humanity.

In its concern about preserving the 'natural' world, the biodiversity agenda stigmatises human activity. The natural is valued indiscriminately, almost religiously, while human intervention - even human existence - is presented as a problem. So environmental writer Mark Lynas can, writing in the mainstream publication the New Statesman, describe humans as 'an infectious plague' displacing 'other living species from the planetary food web' (3) - and this is seen as a reasonable point to argue.

Apart from the anti-human character of the biodiversity agenda, this heightened preoccupation with the negative consequences of human activity ignores many of the facts about how the environment has actually changed. Following the last major extinction event about 65million years ago, when most dinosaurs became extinct, the number of species living on the planet multiplied massively in response to the Earth's slowly changing physical characteristics and the process of evolution. The diversity of species has never been richer than during the relatively brief period that humans have been around. If now, due to human advances and achievements, some species diversity is being lost, then at one level, this is simply more change. There is no divine order unless we wish to turn biodiversity into a new god.

If we are to benefit from the latest insights from science, and decide what is and what is not problematic, our approach needs to be an unashamedly human-centred one. Unfortunately, it is human-centredness that seems in most danger of dying out.

Read on:

spiked-issue: Genetics

(1) 'Comparative losses of British butterflies, birds and plants and the global extinction crisis', JA Thomas et al, Science Vol 303, 19 March 2004

(2) The UK Biodiversity Action Plan, Defra

(3) Mark Lynas, New Statesman, 23 February 2004

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