The Sixth Extinction

The Sixth Extinction, by Elizabeth Kolbert, is an account of how the Earth's organisms have changed over time. The first half of the book touches on the first 5 mass extinctions (the most famous one being about 65 million years ago, when the dinosaurs were killed off). Kolbert discusses the likely reasons for each of the extinctions, and explains how the course of life becomes completely re-routed as some species die off and other survive to pass along their genes and evolve into new species. She also asks how different life on Earth might be if the extinctions had not happened. Would completely different life have evolved? Would humans still be here?

The second half of the book talks about more recent times- since humans have been on the planet. Humans, even in our earliest days, have had huge impacts on the planet. Our keen minds and our ability to craft tools has caused us to eliminate the majority of the large mammals in existence, most of them likely not on purpose. When our species first evolved, we even managed to kill of the Neanderthals (but not without breeding with them first!).

Current humans are having huge effects on the planet and its biodiversity. Climate change is acidifying the oceans and killing off coral. Our fragmentation of wild habitats, especially in the tropics, is killing off all sort of species, many that we haven't even discovered yet. Invasive species are out-competing endemic species. Pathogens and viruses, like the chytrid fungus and white-nose syndrome, are spreading and killing off entire species.

Most of our impact is unintentional. Most of us aren't trying to harm the planet or cause organisms to face extinction. But, like it or not, people change the world around us. Some of this is good change, and humans across the planet are working hard trying to save species from extinction. But most of our impact is negative. From pollution to resource use, climate change to poaching, humans seem to be the ultimate invasive species that has taken over our Earth.

I really enjoyed this book. Although I didn't whip through it like I had expected, I enjoyed reading each thoughtful chapter, and took time to reflect on what I had read. There are a lot of facts and a lot of science, but the chapters read more as an account of history and not like a textbook. It isn't a doomsday account, and really doesn't even talk all that much about global warming. It is more just a presentation of the evidence that surrounds us. Overall this gets a thumbs up and I think I am going to add this to my student's reading list for next term.


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