Tuesday, March 09, 2010

"Humans driving extinction faster than species can evolve"

This doesn't seem like it would be news....

From the Guardian:

For the first time since the dinosaurs disappeared, humans are driving animals and plants to extinction faster than new species can evolve, one of the world's experts on biodiversity has warned.

Conservation experts have already signalled that the world is in the grip of the "sixth great extinction" of species, driven by the destruction of natural habitats, hunting, the spread of alien predators and disease, and climate change.

However until recently it has been hoped that the rate at which new species were evolving could keep pace with the loss of diversity of life.

Speaking in advance of two reports next week on the state of wildlife in Britain and Europe, Simon Stuart, chair of the Species Survival Commission for the International Union for the Conservation of Nature – the body which officially declares species threatened and extinct – said that point had now "almost certainly" been crossed.

"Measuring the rate at which new species evolve is difficult, but there's no question that the current extinction rates are faster than that; I think it's inevitable," said Stuart.

The IUCN created shock waves with its major assessment of the world's biodiversity in 2004, which calculated that the rate of extinction had reached 100-1,000 times that suggested by the fossil records before humans.

No formal calculations have been published since, but conservationists agree the rate of loss has increased since then, and Stuart said it was possible that the dramatic predictions of experts like the renowned Harvard biologist E O Wilson, that the rate of loss could reach 10,000 times the background rate in two decades, could be correct.

"All the evidence is he's right," said Stuart. "Some people claim it already is that ... things can only have deteriorated because of the drivers of the losses, such as habitat loss and climate change, all getting worse. But we haven't measured extinction rates again since 2004 and because our current estimates contain a tenfold range there has to be a very big deterioration or improvement to pick up a change."

Extinction is part of the constant evolution of life, and only 2-4% of the species that have ever lived on Earth are thought to be alive today. However fossil records suggest that for most of the planet's 3.5bn year history the steady rate of loss of species is thought to be about one in every million species each year.

Only 869 extinctions have been formally recorded since 1500, however, because scientists have only "described" nearly 2m of an estimated 5-30m species around the world, and only assessed the conservation status of 3% of those, the global rate of extinction is extrapolated from the rate of loss among species which are known. In this way the IUCN calculated in 2004 that the rate of loss had risen to 100-1,000 per millions species annually – a situation comparable to the five previous "mass extinctions" – the last of which was when the dinosaurs were wiped out about 65m years ago.

Critics, including The Skeptical Environmentalist author, Bjørn Lomborg, have argued that because such figures rely on so many estimates of the number of underlying species and the past rate of extinctions based on fossil records of marine animals, the huge margins for error make these figures too unreliable to form the basis of expensive conservation actions.

However Stuart said that the IUCN figure was likely to be an underestimate of the problem, because scientists are very reluctant to declare species extinct even when they have sometimes not been seen for decades, and because few of the world's plants, fungi and invertebrates have yet been formally recorded and assessed.

The calculated increase in the extinction rate should also be compared to another study of thresholds of resilience for the natural world by Swedish scientists, who warned that anything over 10 times the background rate of extinction – 10 species in every million per year – was above the limit that could be tolerated if the world was to be safe for humans, said Stuart.

"No one's claiming it's as small as 10 times," he said. "There are uncertainties all the way down; the only thing we're certain about is the extent is way beyond what's natural and it's getting worse."

Many more species are "discovered" every year around the world, than are recorded extinct, but these "new" plants and animals are existing species found by humans for the first time, not newly evolved species...

Later this year the Convention on Biological Diversity is expected to formally declare that the pledge by world leaders in 2002 to reduce the rate of biodiversity loss by 2010 has not been met, and to agree new, stronger targets...

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