There have been five mass extinctions in the history of the world. In The Sixth Extinction: An Unnatural History, Elizabeth Kolbert (a science writer for the New Yorker) argues that we are in the middle of, and that we are causing, a sixth extinction. In simple terms that the lay person can understand, she weaves the history of the five major extinctions, and the fate of flora and fauna today, through the stories of a variety of different species. She travels the world, studying animals that are no longer with us, and using them to explain how species have died out. For example, the ammonite, a tiny marine invertebrate mollusk, lived during the cretaceous period. Kolbert uses their history to describe the Cretaceous period and how it ended when a giant asteroid smashed into the Gulf of Mexico (also killing most of the dinosaurs).

At one point, people did not believe in the idea of extinction. It wasn’t until the very end of the 1700’s that Georges Cuvier, a French naturalist, studied the fossils of the American mastodon. The mastodon died out 1,3000 years ago – which Kolbert notes just happens to coincide with the spread of humans throughout the world. Cuvier determined they were a species that no longer existed. His contemporaries believed that these bones were the remains of rhinos or elephants who simply no longer lived in that North America. But Cuvier shocked the world with his theory and helped pave the way for scientists like Charles Darwin, and helped show that species are constantly changing, dying out, and morphing into something new.

Kolbert’s stories that really touched me were the ones that described man-induced extinction. One chapter is devoted to the Great Auk, a 3-ft tall flightless bird that lived on rocky islands in the North Atlantic and the East coast of North America. These birds once were everywhere, and were easily killed as food for visiting ships and even caught for feather pillows and mattresses. They were never able to build up a natural defense to man, and their slow reproduction cycle led to their death as they were overhunted in the 1700’s and 1800’s. The last two known Great Auk’s were killed off the coast of Iceland in 1844 by men looking to capture one for a collector. There are 78 remaining skins of Great Auks out there in the world, in various museums and collections, but the birds will never be seen walking and swimming again.

In a similar manner, we (humanity) are slowly killing off the coral reefs around the world. Kolbert discusses global warming and its counterpart – ocean acidification – and shows how there are traumatic effects of this climate change on huge numbers of species. She visits the Great Barrier Reef and swims among the coral (providing a lengthy and vivid overview of life under the waves), and shows that as the oceans become more acidic, reefs are slowly dying off as they can no longer calcify as fast as they are eaten by fish and beaten by the waves. These major changes in the global climate, which have dramatically taken place as the world has developed industrially over the past 150 years, are driving Kolbert’s ‘sixth extinction’ and are caused “solely by humanity’s transformation of the ecological landscape.”

The book is not all gloom and doom. Kolbert highlights the huge amount of good and the work that many are doing to help save a variety of species. Her best example is an intense description of how zoo veterinarians are trying to impregnate and breed Sumatran Rhinos. She notes that “in an ironic twist, humans have brought the species so low, that it seems only heroic human efforts can save it.” I will leave the details of the breeding work for you to find in the book, but suffice it to say, it gets juicy.

What is missing from this book: I wish Kolbert had delved a little more into the arguments surrounding climate change, even if only to break them down and prove her beliefs. She takes global warming and ocean acidification as entirely man made, and doesn’t acknowledge that some believe otherwise. She does acknowledge that as climates change, new species evolve, but doesn’t really explain the full value of attempting to save older species. There are many reasons (they are beautiful, diversity helps us all, we can learn from other species, etc), but I felt the book could have been strengthened with a discussion of these motives.

Favorite line in the book – “in life, as in mutual funds, past performance is no guarantee of future results.” The world is changing right now, and these changes are driving many species to their end. This is sad and even tragic. But at the same time, new species will develop and the cycle will continue, just like the world of mammals slowly grew out of the death of the dinosaurs. Score: 7.

Note: When I was thinking of buying this book, I read a much more passionate and informed book review by former Vice President Al Gore.  If you are interested, it is worth a read.