The Song of the Dodo
This is a book of physical adventure — travels in exotic and even dangerous places to see extraordinary creatures. It is also a book of intellectual adventure, in which the excitement of new understanding builds over 600 pages until at last the baton is passed to the reader. This is only fitting because the last sentence will leave more than a few readers on their feet, punching the air with a fist and saying "Yes!"
David Quammen is a Montana novelist who for the past 15 years has written a formidably researched column for Outside magazine. (The final one, on his fear that all surviving animals will end up as tame as city pigeons, appeared in the March issue.) For the past eight years he has traveled the world on a Guggenheim grant to see for himself some of the most endangered animals on the planet. For all those years and more he has been talking to biologists, sometimes in their university offices, other times on trails in Madagascar, in the Atlantic forest of Brazil, on what is left of Krakatau or on Guam at night, looking for brown tree snakes. He has walked Tasmanian trails where thylacines once roamed and been ambushed on a trail in Indonesia by a Komodo dragon.
His subject, Quammen says, is "the extinction of species in a world that has been hacked to pieces." To some, extinctions within an ecosystem are "relaxation to equilibrium." Others say "faunal collapse." Quammen prefers the phrase of the Smithsonian's Tom Lovejoy: "ecosystem decay."
He begins with travels in Indonesia, following in the footsteps of the self-supporting British naturalist Alfred Russell Wallace, who figured out natural selection at the same time as Darwin. He spends time in the Galapagos. Baja California. Mauritius.
The book fills us in on some of the great field biologists, and little by little we become comfortable with the jargon, understanding adaptive radiation and trophic cascades. We follow their progress and their battles as they struggle to understand how life works.
A milestone in that saga comes in 1967 when Robert MacArthur and Edward O. Wilson publish a mathematical treatise called The Theory of Island Biogeography. (Biogeography is the study of what organisms live where — and why.) MacArthur and Wilson argue that the number of species on any given island represents a balance between immigration and extinction. The species themselves may change as some become extinct and new ones arrive, but there is for every island an equilibrium.
Quammen explains why islands are a good place to start. "Islands are distinct from mainlands in that they represent simplified, exaggerated versions . . . of exactly those evolutionary processes that occur on mainlands." Wilson is no mere theorist. He and his then graduate student, Dan Simberloff, tested the theory in Florida Bay. They censused the insects on minute mangrove islands, then had a professional exterminator from Miami wrap the islands in canvas a la Christo and fumigate them. After several years they censused the islands again. Their insect populations all had equilibrated around their original numbers.
MacArthur and Wilson, of course, knew they were talking about more than islands surrounded by water: "Insularity is moreover a universal feature of biogeography." Four years later James H. Brown pointed to one example of nonequilibrium insular biogeography. The tops of mountains in the Far West's Great Basin are effectively islands, he said, with animals and plants from a colder time stranded there since the last Ice Age. These sky islands have no immigration, only extinction. This, Quammen concludes, is the phenomenon of ecosystem decay. And, he adds, the theory applies to all fragmented habitats, which means all habitats.
Quammen explains that on true islands, mammals tend toward dwarfism and reptiles toward giantism. We know from fossil evidence that a pygmy elephant, only five feet high, once lived where the Komodo dragon does today. This juxtaposition led polymath Jared Diamond to speculate in a paper for Nature: "Did Komodo Dragons Evolve To Eat Pygmy Elephants?" Who could resist a title like that?