Andreas Späth

We’re causing a mass extinction!

2014-06-09 15:13

Andreas Wilson-Späth

It's official: human activities, intentionally or not, are killing off animal and plant species at a catastrophic rate.

To a future geologist, one of the defining characteristics of the Anthropocene, the period during the earth's history in which humans pervasively transformed the biosphere of the entire planet, will be a mass extinction event that wiped out 75% or more of all species forever - quite possibly including Homo sapiens itself.

Reviewing the distribution, conservation and extinction rates of all complex life forms, a paper recently published in the journal Science concludes that "current rates of extinction are about 1000 times the background rate of extinction".

That is, animal and plant species are disappearing 1 000 times faster today than they did during the entire history of life prior to the rise of modern human civilisation. This figure is higher than previously believed, but the authors of the study think it is still likely to be an underestimation.

New species arise very slowly. Each vertebrate species, for instance, is thought to produce a new species once every 10 million years or so. But even at this slow pace, new species have appeared faster than old ones have vanished for almost all of the time that life has existed on earth.

The exceptions to this have been a number of geologically short-lived yet extremely dramatic episodes captured in the fossil record as mass extinction events. Among the "Big Five" mass extinctions, the most famous is the Cretaceous-Paleogene extinction event 66 million years ago, which eradicated 75% of all species alive at the time, including the dinosaurs. The most devastating was the Permian-Triassic extinction event, which eliminated up to 96% of all species 185 million years earlier.

Scientists believe  that current global extinction rates are as fast or faster than they were during the Big Five mass extinctions and that the world is in for a similarly massive die off of life forms within the next few centuries.

The major difference is that previous mass extinctions are thought to have been caused by events like gigantic volcanic eruptions, precipitous drops in sea level and asteroid impacts, whereas the present situation is the result of problems created by humans such as agricultural expansion and overexploitation, deforestation, pollution, the effects of global warming and the spread of invasive aliens, all of which have resulted in a widespread denigration and loss of natural habitats.

To give a local example, some climate change models forecast the extinction of up to 65% of the species endemic to the Cape's fynbos by 2050.

It's not all bad news, though. Conservation does work and we do still have the opportunity to soften the impact we're having on the plants and animals we share this planet with.

Research indicates that without the conservation efforts that are being made around the world right now, losses in biodiversity would be substantially higher than they already are, but it also suggests that much more is needed to turn the situation around.

Detailed studies of the most vulnerable species, including, for instance, these fantastic maps of global biodiversity, will go some way towards allowing conservationists to fine-tune their work.

More troubling is a recent idea referred to as "biodiversity offsetting" in which companies would be permitted to destroy the environment in one locality as long as they made a financial contribution towards the restoration of the biosphere somewhere else.

A market place for trading in "biosphere credits" akin to the system that allows the world’s worst air polluters to greenwash their image through carbon offsetting while continuing their dirty business as usual. If you ask me, the one sounds as retarded an idea as the other.

- Andreas is a freelance writer with a PhD in geochemistry. Follow him on Twitter: @Andreas_Spath
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