The Sixth Extinction: An Unnatural History by Elizabeth Kolbert

audiobook read by Anne Twomey.

The Sixth Extinction: An Unnatural History is about how we as a planet are currently undergoing the sixth great extinction event. This event is largely because we (humans) have spread to every environment and those that we don’t live in we still affect through our actions.

In the geologic record there have been five major extinction events, some due to climate change, some due to asteroid impacts or volcano eruptions, some due to a drop in sea level. Over the billions of years years that the Earth has been around, these events only happen every hundred million years or so, and in a geologic time scale they can happen quickly. Relative to human scale, “quickly” can still encompass all of human (homo sapiens) history. We’ve been around for the blink of a geologic eye. In that time span we’ve started the sixth major extinction.

Kolbert frames each chapter out as a story about a single species, and how that species is an indicator of a larger trend. For example she talks about the Panamanian golden frog as an example of a disappearing species, but uses it as an example of a larger trend of amphibians around the world going extinct (the leading theory is that a mite from an African frog has spread worldwide and kills amphibians). The Great Auk was one of the first species observed to go extinct from human interaction (hunting for food, feathers and collecting, the last pair of Great Auks was killed at the request of a merchant who wanted a specimen).

Kolbert also highlights important historical figures to give context to and highlight important ideas about extinction. For example in the chapter about Mastodons, she talks about how Gorges Cuvier used the teeth and bones being discovered in the 18th century to theorize that species could disappear from the world entirely. In the chapter about Galapagos tortoises she gives an overview of Charles Darwin’s life and his work that led to evolution and natural selection.

She also talks more generally about not individual species, but areas and habitats that are in danger. She spends time at a coral reef diving and observation station in the Pacific to tell the story of the oceans in general. With the increase of carbon dioxide (C02) in the atmosphere, oceans are becoming more acidic as they absorb more and more of the CO2. When this happens coral have to work harder and harder to create the reefs, eventually the oceans could become so acidic that not only will coral not be able to build new reefs, old reefs will start to dissolve. Another habitat that is vulnerable is the rain forests, trekking into the deep Brazilian rain forests to observe the complex habitats and highly specialized species that inhabit them. As more and more people venture into the jungle we segment parts of it to create farm land, this fragmentation can lead to stress on highly specialized species that can lead to extinction. At the same time Kolbert also talks about how climate change of even a few degrees can lead to disaster for the hyper-specialized species that inhabit specific areas of the rain forests.

On of the other larger trends that Kolbert talks about is the reversal of millions of years of continental drift through human interaction. Like the Panamanian Golden Frog being wiped out by invasive mites from Africa, bat species in New England are being decimated by an invasive fungus from Europe. Plants and animals are moving to different parts of the world and pushing out native species. Sometimes a new species is introduced and it can’t handle the new environment, sometimes it can overrun the new environment that it was unleashed upon (like the Emerald Ash Borer beetles or Chestnut blight fungus wiping out American ash and chestnut species respectively).

While this does seem like a very negative book, Kolbert is trying to shock you into action. She ends on a message of hope, talking about the Hawaiian Crow. There only a few hundred of the birds left, but we are going to great lengths to save him, almost absurd lengths. We (humanity) have caused great damage, but we are now recognizing the impact that we’ve had, and can start undoing and mitigating the damage. If we can get our act together, we might be able to slow down the sixth extinction.

Overall a very good book. The personal narratives intermixed with research and history that Elizabeth Kolbert crafts is a very engaging book. It intermixes the science with accessible details about people or species or other relevant facts. I can clearly see why this was rated as one of the best science books of 2014. The audio book is read by Anne Twomey, who reads almost like a voice synthesizer, with very subtle inflection, to the point of almost being robotic. This was off putting at first but eventually grew on me as a soothing monotone.


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