The Cresting wave of the sixth extinction

I’ve just read an incredible piece in The Guardian by Jan Zalaziewicz, a professor of paleobiology at Leicester University. A recent study conservatively estimates that over 450 vertebrates have gone extinct since 1900. If we state those numbers as an estimate versus a conservative rate of what nature does itself, that’s 10 to 100 times the rate of extinction. Other estimates have placed the rate at over 1,000. But the study Zalaziewicz writes about tried to be conservative, to avoid the chicken little effect.

This section struck me, for both its starkness and the elegance of its language:

The scientist Vaclav Smil, of the University of Manitoba, has calculated that simply measured by mass, humans now make up a third of land vertebrates, and the animals that we keep to eat – cows, pigs, sheep and so on – make up most of the other two thirds. All the wild animals – elephants, giraffes, tigers and so on – are now less than 5% by mass. It’s a measure of how they have been pushed to the fringes by humans.

Humans change things in other ways – they now direct the evolution of the animals that are useful to them, by breeding and by genetic engineering: again, it’s a planetary novelty. The energy our species obtains from photosynthesis is not enough, and so we mine stored photosynthetic energy from the ground, as hydrocarbons, in enormous amounts, and use that to power our machines.

These machines – cars, planes, computers and much else – have, together with their human software, been termed the technosphere by the geologist Peter Haff of Duke University. He views it as an emergent system with its own internal dynamics (and which humans currently drive but don’t really control) – in effect an offshoot of the biosphere. Whatever it is, it is evolving at lightning speed by comparison with biological evolution.

There is already widespread agreement among scientists that we live in the Anthropocene, the age of humans. But there is some disagreement about when it started. Perhaps the technosphere will give us a clue.


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