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The Sixth Extinction by Elizabeth Kolbert – review

 
Rainforests

Rainforests are under threat. Photograph: Wayne Lawler/Ecoscene/Corbis

 

Powered by Guardian.co.ukThis article titled “The Sixth Extinction by Elizabeth Kolbert – review” was written by Caspar Henderson, for The Guardian on Friday 14th February 2014 10.30 UTC

One day around 66m years ago – it was in June or July if the evidence from fossilised pollen traces has been interpreted correctly – an asteroid somewhat larger than Manhattan ploughed into the Earth near what is now Chicxulub in the Yucután Peninsula, Mexico at 45,000 mph. As it hit with a force equivalent to more than 100m megatons of TNT, or about 1,500 times the total content of the world’s present nuclear arsenals, the asteroid sent a vast cloud of scalding vapour thousands of miles in all directions, and blasted more than 50 times its own mass of pulverised rock high into the sky where, as tiny particles, it incandesced and heated the entire atmosphere to several hundred degrees centigrade, killing almost everything unprotected by soil, rock or deep water. Many scientists believe that about three-quarters of animals, including the pterosaurs, the mosasaurs and, as every child now knows, the non-avian dinosaurs were wiped out as a result. It took millions of years for life to recover and surpass its previous diversity, this time with a new ensemble of species that included our distant ancestors. This event, known as the Cretaceous-Paleogene (and formerly as the Cretaceous-Tertiary) extinction, is counted as one of five mass extinctions over the last 500m years or so, where a mass extinction is defined as an event in which a significant proportion of life is eliminated in a geologically insignificant amount of time.

The Sixth Extinction: An Unnatural History by Elizabeth KolbertAt first glance, the footprint of industrialised humanity on the biosphere may look small compared with that of the Chicxulub asteroid. The additional input of heat into the world’s oceans resulting from greenhouse gases put there by the combustion of fossil fuels, for example, is equivalent to only about four atomic bomb detonations, or well under a tenth of a megaton per second. But first glances are sometimes misleading. Humans are affecting the Earth system in many ways, and have been doing so every moment for decades and indeed centuries. It may seem like a diffuse, drawn-out affair to us as individuals but compared with many natural processes (for which animals and plants are, in Jacob Bronowski’s phrase, equipped with “exact and beautiful adaptations”), it is virtually instantaneous. Perhaps the current transformation will turn out to be more like the end-Permian 252m years ago, the third of the “big five” extinctions, which is thought to have been kicked off by massive pulses of carbon dioxide to the atmosphere, each of which lasted only a few decades, but which together resulted in the death of up to 95% of all life.

Or not. A lot is uncertain. What is beyond reasonable doubt is that something big is under way. The best estimates are that the Earth is losing species at many times the background rate (the natural churn in which a few species go extinct every year while new ones evolve), and that 30% to 50% will be functionally extinct by 2050.

The plight of the non-human world has inspired many works of popular science over the last 20 years or so. A 1995 book by Richard Leakey and Roger Lewin, presciently titled The Sixth Extinction, David Quammen’s The Song of the Dodo, in 1996, and numerous essays by EO Wilson are among those that speak with clarity and urgency. Books about the death of single species, from Sam Turvey’s Witness to Extinction (2008) about the Yangtze river dolphin to Joel Greenberg’s A Feathered River Across the Sky (2014) about the passenger pigeon sometimes reach substantial audiences. John Platt’s Extinction Countdown is one of many useful blogs on the web. The calamity has inspired artists too. Maya Lin continues to develop a remarkable project titled What is Missing?. Extinctathon, a computer game imagined by Margaret Atwood in her Oryx and Crake trilogy (2003-13), now exists in the real – virtual – world. In The Road (2006), Cormac McCarthy disgorges a nightmare of a world that humans have killed.

But with extinctions and new discoveries piling up, there is a need for still more studies. And in The Sixth Extinction, Elizabeth Kolbert, a staff writer for the New Yorker, offers well-composed snapshots of history, theory and observation that will fascinate, enlighten and appall many readers.

Kolbert begins with a visit to a research station in Costa Rica, where researchers are documenting the disappearance of the golden frog, Atelopus zeteki. Amphibians, the class that includes frogs, are the most endangered group of animals in the world, with an extinction rate as much as 45,000 times the background rate.

 

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