On one fateful day 66 million years ago, the Earth’s gravitational field captured an asteroid. It was travelling at around seventy thousand kilometres per hour on a flat trajectory. It slammed into the Yucatan Peninsula and generated a white-hot, supersonic shock-wave which was directed mainly northward. The author of this book quotes a geologist who said: “Basically, if you were a triceratops in Alberta, you had about two minutes before you got vaporized (sic)”. Trillions of tons of sulphur- rich material were blasted into the air, which led to a condition analogous to a ‘nuclear winter’. Whole orders, families, genera and species of plants and animals went extinct – most famously the non-avian dinosaurs. It took the world millions of years to recover from these catastrophic circumstances – but they are probably why we’re here, rather than some descendant of the dinosaurs.
There had, in fact, been four mass extinction events before the one described above. The most devastating was probably the one at the end of the Permian, some 252 million years ago when around 96% of all living things went extinct – although the reasons for that event are not as well understood. When interviewed recently (http://www.theguardian.com/theobserver/2014/mar/09/elizabeth-kolbert-whole-world-becoming-zoo) the author of this book, Elizabeth Kolbert, stated that life on Earth is “contingent” i.e. subject to chance or unforeseen circumstances. The title of her book is based on the rapidly growing consensus among scientists that we’re now living through the sixth extinction event in the history of life on Earth – and that our own species, Homo sapiens, is directly responsible for it. Our current epoch is increasingly being referred to as the “Anthropocene” because our species is now so dominant and has so modified the planet’s surface and atmosphere that the fate of the biosphere is now in our hands.
Elizabeth Kolbert is an American journalist and author. She is best known for her book on climate change, ‘Field Notes from a Catastrophe’ (2006), and as an observer and commentator on environmental matters for the ‘New Yorker’ magazine. This present book is brilliant, lucid, very readable, scientifically up-to-date, tragic and utterly terrifying. We learn that although certain species, such as the Great Auk and the Dodo, have been deliberately exterminated through over-exploitation in the recent past, more recent losses can be directly attributed to our gross and ruthless modifications of the planet’s surface and atmosphere – in particular there are direct links between species’ extinction and climate change. For example, carbon dioxide is soluble in water and produces a weak acid. As the CO2 content of the atmosphere increases, the oceans become more acidic. This affects the viability of organisms that use calcium in their body plans; shellfish and corals are particularly badly affected. In tropical waters, reefs formed by corals provide ecological niches for thousands of non-coral species; if corals are damaged or killed, all of those dependent species are put at risk as well. Tropical rain forests contain hundreds of different tree species. Each tree species has specific habitat requirements and also provides niches for many other species of plants and animals. As temperature rises, trees which produce few seeds and/or are slow growing are at a serious disadvantage, and, consequently, so are their attendant species. Trees which produce lots of seeds and/or are fast growing can move uphill to cooler climes. But even the latter are still at risk because many rain forests are now so fragmented that there are limited spaces for them to move to.
The much vaunted ‘globalisation’ is a serious problem too. Many organisms have been (often inadvertently) transported around the world and have caused havoc in places in which they do not belong. Currently, Central American amphibians and North American bats are being wiped out by imported fungal diseases.
I took away two surprising ideas from this book:
1. This is undoubtedly the first extinction event in history which is being studied, in meticulous detail, by elements of the causal agent! In her research for this book, Ms Kolbert interviewed many scientists working in the field and accompanied some of them on their field trips. The ingenuity and dedication of these scientists is often astonishing.
2. Time scales can often be difficult, or impossible, to grasp; who can get their head round 66 million years – let alone 252 million years – for example? It is now, more or less, agreed that when humans migrated out of Africa, they exterminated large animals (mammoths, giant ground sloths, moas etc.) everywhere they went. Kolbert interviewed a paleobiologist, named John Alroy, who described this ‘megafauna extinction’ as a “geologically instantaneous ecological catastrophe too gradual to be perceived by the people who unleashed it.” The ominous fact is, though, that extinctions are currently happening within single human lifetimes.
Dave Bishop, March 2014
Note: This review first appeared in 'Manchester Climate Monthly'. To find out more about Manchester's premier climate journal, you should e-mail the editor, Marc Hudson, on firstname.lastname@example.org.
PS: I tried to add a picture of the cover of this book to top of this article but, for some unknown reason, this - bleep, bleep, bleep, bleeping - software wouldn't let me!!