The Sixth Extinction: An Unnatural History


Elizabeth Kolbert




Date Reviewed:

May 29, 2015

award this book a four star rating, which is a strong endorsement that it is a good read. Yet, I caution you that you may not want to read it, because it will leave you depressed. The author, Elizabeth Kolbert, gives some stunning information on the rate at which our fellow creatures are disappearing from our planet - species are going extinct at an accelerating rate, and there is convincing evidence that homo sapiens is to blame. The title, the sixth extinction, refers to the fact that there have been five previous catastrophic events in the Earth's history where a large percentage of the species perished. The most recent of these extinctions was the famous astroid strike in Mexico that wiped out the dinosaurs. Currently, species are now going extinct at a rate comparable to those five previous tragedies - it seems like a slow motion disaster to us, because our lifespans are so short, but measured in geologic time, it is as if all these species are disappearing at once.

Kolbert does an excellent job describing different parts of the biosphere and explains how each of them are degraded and becoming more fragile, their plants and animals at risk of disappearing.

Here are some of the topic she covers: the disappearance of gold frogs in Costa Rica - once these were common amphibians, but now they are missing from the landscape. Indeed, amphibians are suffering throughout the world. The acidification of the ocean - higher levels of carbon dioxide in the atmosphere result in higher levels of CO2 in the ocean waters. The result is slight acidification of the ocean waters, but the small change is enough to cause calcium carbonate to dissolve, which means that creatures won't be able to grow hard shells. Even worse, the acidification of the ocean waters kills off the coral. If the reefs die, it will have a catastrophic impact on the marine ecosystem; yet Kolbert projects that within my expected life span all the coral reefs will perish.

It's not just climate change that is killing the animals. Globalization has resulted in species transported around the world (did you know that earthworms were brought over to the new world in the bilge of sailing ships, apparently earthworms are not native to the new world.) Now rats and beetles and pythons and asian carp are introduced into environments in which they have no natural predators, these creatures thrive by wiping out the defenseless native species (think of the brown tree snakes in Guam, wiping out all the bird populations). Humans also wipe out native species by destroying their native habitat. As we log the forests and plow the grasslands, there is not enough land left for the original animals to survive. We can set aside small parks of native landscape, but these are generally to small to allow for a healthy population of animals to thrive.

There is a lot of interesting material here, but ultimately the final verdict is depressing. There is more carbon dioxide pumped into the atmosphere every year, and every year the human population grows larger, consuming more of the resources of the entire biosphere, leaving less and less for the wild animals.