American Scientist

No Way Home: The Decline of the World's Great Animal Migrations. David S. Wilcove. x + 245 pp. Island Press, 2008. $24.95.

Conservation biology focuses largely on developing solutions to the human-caused extinction crisis gripping the world's biota. Somewhat diminished amid the valiant efforts to save threatened species and populations is the complementary goal of maintaining the grandeur of certain natural phenomena, including ones that capture the imagination by virtue of the sheer abundance of organisms involved. A prime example, which David S. Wilcove describes eloquently in No Way Home, is animal migration—the back-and-forth journeys of flocks, herds, pods and schools of animals across plains and seas, and sometimes even hemispheres. These grand migrations have evolved over millions of years to allow animals to take advantage of seasonal flushes of food. Yet the patterns of movement are indeed dynamic and can change noticeably over a fairly short period of time.

No Way Home explores the current precarious state of migration, raising a fundamental question for conservationists: How satisfying will it be to save all of the migratory species from extinction if the flow of migration nevertheless slows to a trickle? Migration is indeed declining. In some cases the changes have been abrupt and obvious, but more often they have taken place so slowly as to be barely perceptible until eventually it becomes obvious that a particular migration is an unrecognizable ghost of the phenomenon it once was.

Wilcove's account is compelling. He paints a colorful picture of migration, supplying readers with many anecdotes about his encounters with various species on the move and the scientists who study them. The book is short and quite readable, and I feel comfortable recommending it to anyone interested in nature or conservation—even research scientists and conservation professionals, who might benefit from stepping back from their areas of specialization to admire migration from a more distant vantage point.

The loosely organized stories that make up No Way Home have been selected for the broad geographic and taxonomic coverage they collectively offer. By the time readers finish the book, they will have visited North and South America, Africa and the seven seas (Asia and Australia get short shrift) and will have learned something about the migration of songbirds, shorebirds, butterflies, locusts, wildebeest, zebras, gazelles, springbok, bison, elk, pronghorn, right whales, sea turtles and salmon.

These descriptions all highlight the dramatic and emotional appeal of migrations. The spectacle of an immense aggregation of creatures—a swarm of locusts, say—provides roughly the population-level equivalent of the "charisma" that has been attributed to individuals of some species. Another theme of these stories is that scientists have discovered many fascinating and unexpected aspects of migration, often by means of technologies such as satellite tracking or stable-isotope analysis—a promising new approach in which biologists measure the ratio of heavy to light stable isotopes of particular elements (hydrogen, nitrogen or carbon, for example) in feathers or bone to determine the geographic origins of the tissue and thus the breeding grounds of the migratory animal.

And a third focus is on the major threats to migration, attributable for the most part to human activity: destruction of habitat; obstacles such as dams, skyscrapers, fences and roads; overhunting and overfishing; and climate change.

The animal migrations most compatible with a human presence seem to be those of birds, because they are better able to coexist with us as our growing population wreaks havoc on the landscape we share with them. For one thing, our roads and fences and dams don't fetter them. In addition, for most of us, birds are the creatures whose migrations are most readily observed. By visiting a local park or even just taking a walk around the neighborhood, we can see birds in transit and perhaps feel the hemispheric connections they evoke. This sense of immediacy should make it easy to develop grassroots support and workable strategies for protecting migratory songbirds in the Americas, where in general they are loved and do not cause problems. Where will such efforts work if not here, and for which species if not these?

Wilcove gives preeminence to migratory birds, appropriately I believe, by making them the subject of the first and longest chapter, "Empty Skies." For this reason, and because I'm a bird specialist, I am concentrating my detailed remarks on the book's treatment of birds. However, readers should keep in mind that a good three-quarters of the text is devoted to land and sea migrations.

The "Empty Skies" chapter is good, but I was disappointed that it didn't contain more detail about the fascinating adaptations that enable migratory birds to survive their long journeys and thrive along the way. And I found Wilcove's discussion of the conservation issues and the science behind the documentation of migratory bird declines to be a bit dated: For the most part, he is presenting arguments and information that have been available for decades. Also, I wish that he had given more attention to such topics as the expected effects of climate change, including the rapid changes anticipated in arctic and alpine regions, the drying of prairie wetlands and the flooding of nesting areas by rising sea levels.

An area of intense concern and interest that Wilcove fails to explore is the rapid spread of epizootic diseases as two systems involving the global movement of birds collide: the migrations of wild birds and the massive factory-style production of poultry that is shipped and sold around the world. The sobering changes resulting from the production of biofuels are also worth discussing. However, the effects on habitat of having more acres under cultivation to satisfy the biofuel boom are so recent that conservation biologists are just beginning to become aware of them. Thus it is perhaps not surprising that a book whose manuscript was probably completed early in 2007 doesn't comment on them.

Wilcove does not devote a lot of space to prescribing solutions—No Way Home is more of a lament about what has come to pass than a strong call to action. And although he does mention a number of conservation efforts, he doesn't go into much detail about them. That's a shame, because in some areas real progress is being made.

In the realm of migratory bird conservation, for example, recent advances include the expansion of "Partners in Flight," a program that now covers most North American migratory birds; the 1993 founding and subsequent celebration of International Migratory Bird Day; and the sea change in attitude toward the conservation of nongame birds, which mirrors the rapidly increasing popularity of bird-watching. In addition, there has been a tremendous increase in the number of scientists and conservation professionals in this hemisphere who are interested in migratory birds. I am sure that similar grassroots movements are sprouting up around most of the imperiled migratory animals discussed in the book. By not treating these in depth, Wilcove misses an opportunity to inspire readers to participate.

He does argue that increased international cooperation is needed to develop key protected areas along migration routes. I agree, but I believe that the full splendor of the seasonal movements of migratory animals will not be maintained solely or even primarily through international cooperation to establish and maintain reserves. Human-managed lands see the most migratory traffic, and this reality calls for bold and creative approaches, such as the development of habitat corridors and the marketing of shade-grown coffee and cocoa to environmentally conscious consumers. After all, most migratory species can thrive in the countryside around reserves if some attention is paid to their requirements.

Although more study is needed to determine just what those requirements are, migration research over the past decade has helped to foster the conservation of biodiversity using several innovative approaches, including the enhancement of agricultural lands. With more work, and a little luck, other successes will follow. We can thus hope that at least some of the spectacular animal migrations that are now imperiled will be around for future generations to appreciate firsthand.