Everything you might want to know about life and death on islands here, there, and everywhere on the globe can be found in Quammen's study of island biogeography.
The National Magazine Award-winning science writer (Outside magazine; The Flight of the Iguana, 1988, etc.) asks, Why does island life differ radically from mainland life? The answer, not surprisingly, is evolution. There are unique evolutionary opportunities as well as pressures on islands. On oceanic islands, which arise from deep sea eruptions (such as the Galapagos Islands), there may be fewer varieties of species; the first arrivals often expand to fill all sorts of ecological niches in a process called adaptive radiation. So it was with the varied populations of finches that Charles Darwin observed in the Galapagos. Islands that sit on continental shelves near enough to mainlands to have been connected by land bridges at times of major glaciation may have animal species as varied as those on the mainland, but the species are likely to differ in their behavior or appearance from mainland relatives. Some reptiles isolated on islands grew large, like the Komodo dragon of Indonesia; some mammals shrank, like the pygmy elephants found in Sicily. Some birds became flightless, like the celebrated dodo native to Mauritius. Quammen provides abundant examples of the variables that can foster or doom populations, ranging from the sheer size of an island (big is better), to bouts of bad weather, to the introduction of farming and the animal camp followers of man: pigs, rats, and cats.
The book's virtues include Quammen's vivid account of his treks to the world's wild places and interviews with the experts he finds there. The downside is too much of a muchness; Quammen's zeal to spill all his notes and a breezy style that grows wearying. Taken in small bites, however, there is much to glean here about the wonders, and also the fragility, of life on earth.