The Sixth Extinction Summary

The Sixth Extinction explains how human activity is contributing to a rapid loss of species. Earth has experienced five major mass extinctions in which a large proportion of life disappeared. Elizabeth Kolbert argues that humanity may now be causing a sixth through climate change, habitat destruction, pollution, overexploitation and the movement of invasive species and diseases. She combines scientific explanations with reports from forests, oceans, laboratories and endangered habitats. The book received the 2015 Pulitzer Prize for General Nonfiction. Its central warning is that humans are transforming the planet so rapidly that many species cannot adapt or survive.

1. Mass extinction differs from ordinary extinction: It occurs when exceptionally large numbers of species disappear within a relatively short geological period.

1. Earth has experienced five previous mass extinctions: These events were caused by massive environmental disruptions.

1. Humans have become a geological force: Human activity now changes climate, landscapes, oceans and biological systems on a planetary scale.

1. Habitat destruction eliminates species: Forest clearing, urban growth and agricultural expansion remove the environments on which organisms depend.

1. Climate change shifts natural conditions: Species unable to migrate or adapt rapidly may decline or disappear.

1. Ocean acidification threatens marine life: Carbon dioxide absorbed by oceans changes water chemistry and harms organisms that build shells or skeletons.

1. Global travel spreads invasive species: Organisms and diseases introduced into new ecosystems can devastate native populations.

1. Species exist within networks: The loss of one organism can affect predators, prey, plants and ecological processes.

1. Human intelligence creates responsibility: The species capable of understanding extinction also possesses the greatest ability to reduce it.

1. Important quotation: “In pushing other species to extinction, humanity is busy sawing off the limb on which it perches.” - Paul Ehrlich, quoted in the book.