The Fragmentation of the World's Ecosystems

The main ecological theme to Quammen's book is that the large natural areas of the world are being continually divided into smaller pieces, forming what are essentially islands of habitat just as isolated from one another as islands in the ocean. Island biogeography, which studies how species evolve and go extinct on natural islands, can show us what kind of impact we can expect on species that are isolated by this activity.

As an example of this kind of fragmentation, Quammen writes about the Brazilian rainforest where it is being cleared to provide pasture for cattle. This clearing can create isolated pieces of forest surrounded by grassland. Birds and flying insects may cross these clear areas, but other animals that rely on continuous tree cover will not. The smaller size makes prey and shelter to scarce for larger land animals and they disappear...