The Sixth Extinction Summary
by Elizabeth Kolbert

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The Sixth Extinction Summary

American journalist Elizabeth Kolbert authored The Sixth Extinction: An Unnatural History in 2014. This is a nonfictional account of what Kolbert named "the sixth extinction": an extinction event caused by humans similar to ones that destroyed earlier forms of life, like the dinosaurs and megafauna. 

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Chapter one details the ancestry of frogs and examines the timeline of amphibians on Earth, as well as the increase in frog extinction rate. Kolbert argues that the observed extinction rates, which are exceeding expected background extinction rates, suggest that catastrophe is ahead for Earth. Humans are key to the extinction of Panamanian frogs due to their spreading of the Chtrid fungus, which is not native to Panama. Thus, Kolbert sees humans as significantly responsible for introducing invasive species. 

Chapter two examines catastrophism and the argument that a sudden, violent natural catastrophe must have been at fault for the extinction of the American mastodon. This positions catastrophe as a mechanism of extinction.

Chapter three takes a look at the great auk, a species which died out in 1844 due to overexploitation by human settlers in Iceland who used the bird for meat, fish bait, and much more.

Chapter four looks at the dust created by the Cretaceous-Paleogene extinction event, which resulted in many species—excluding the ammonites—dying out. This illustrates that the advantageous nature of some traits can be altered by a single moment. 

Chapter five examines glaciation and the extinction of graptolites and other clades. The decrease in sea level as a result of dropping carbon dioxide levels caused a huge change in the chemistry of the ocean. Human activity is a contributor in this through the damming of major rivers, the use of accessible freshwater run-off, the removal of primary producers from oceans, deforestation, and use of fossil fuels. 

Chapter six depicts the rising concentration of carbon dioxide in the air due to the burning of fossil fuels and deforestation, which has resulted in the production of carbonic acid in oceans, the drop in pH of those oceans, and the death of marine life.

Chapter seven details ocean acidification and the extinction of...

(The entire section is 527 words.)