What Do Birds Do for Us?
Some might not realize the tangible value of birds, but it would be foolish to underestimate how tough life would be without them.
Odds are, if you're reading this magazine, you feel a moral and aesthetic imperative to support bird conservation. With an estimated 1,200 species facing extinction over the next century, and many more suffering from severe habitat loss, the impulse to protect birds must be universal. Right?
Well, if you happen to be a birder or a biologist, then "of course, birds have an intrinsic value, and we have an ethical obligation to conserve them," says University of Utah ornithologist Cagan Sekercioglu. But bird enthusiasts don't add up to a social consensus. "A lot of people want something more utilitarian," he points out. Elected officials face competing constituent pressures; corporate executives must answer to shareholders; working folks have more immediate economic concerns. If we want policy makers and the public to take conservation seriously, then perhaps we must offer credible research showing that healthy bird populations are essential to human welfare.
Fortunately, there's plenty of proof. Birds keep farmers in business. They protect our drinking water by preventing erosion. They slow the spread of disease. They keep the furniture industry supplied with timber. They provide critical environmental data. The list continues ad infinitum. The collective term for the many ways birds (and other animals, plants, and landscapes) support and improve human life is "ecosystem services." Understanding these services, and quantifying their dollar value, has been a growing priority for scientists worried about the unprecedented loss of biodiversity we're now seeing--by one popular estimate, some 27,000 plant and animal species each year, many of them driven extinct by human activity.
"Until the next asteroid slams into the planet, it's people that will dictate the future course of all known life in the universe," says Gretchen Daily, director of Stanford University's Center for Conservation Biology. "On our own watch--this 100-year span--we're projecting that half of all plants and animals that were on the planet before humanity became a big force will go extinct. Whatever survives really is a function of our activities. I just find it stunning to think about how dramatic the changes are that we're bringing about."
The past decade has seen an explosion of sophisticated research--and the result is a strong body of evidence debunking the myth that bird protection is an unaffordable luxury. "For better or worse, economic arguments tend to get more attention in political debates," says Geoffrey Heal, a microeconomist at Columbia University Business School. The new research, he says, strengthens the case that "most environmental conservation, if well structured, actually does pay off directly."
When the Mormons settled Utah in the 19th century, their first two crop seasons were destroyed by western crickets. "Promising fields of wheat were cut down to the ground in a single day," naturalist Edward Howe Forbush wrote in 1922. "The people were in despair. Then sea gulls came by the hundreds and thousands, and, before the grain could be entirely destroyed, devoured the insects, so that the fields were freed from them. The settlers regarded this as a heaven-sent miracle."
Modern history is filled with anecdotal examples of birds saving potato fields, fruit orchards, and cranberry bogs from insect devastation. Now researchers are studying the phenomenon more formally, trying to quantify birds' value as living pest controllers. They're starting with a much-loathed insect called the coffee berry borer.
Borers are the bane of coffee farmers, many of whom are small landholders in developing countries. The tiny insects take over individual berries and spend almost their entire life cycles inside, rendering those beans unsellable. There are no safe pesticides that kill the insects, and attempts to control them with parasitic wasps show, at best, limited success. "You work all year to protect your crop the best you can," says Peter Williams, who co-owns Kew Park Estate, a 44-acre shade-grown-coffee farm in western Jamaica. "If you're dealing with infestation rates of anything like 20 percent--which some years we do--then you're talking about a very significant economic effect."
What helps save Jamaican farmers from ruin are neotropical migrants like the black-throated blue warbler, whose slate-blue males and olive-green females hop and fly through vegetation foraging for insects, and the American redstart, known locally as the butterfly bird for its flitting motion and black-and-orange male plumage. These and other birds feast on the borers while the insects are first drilling through the berries' epidermis.
Matt Johnson, a professor of wildlife habitat ecology at California's Humboldt State University, has studied the birds in Jamaica's Blue Mountains--a steep and meandering landscape that produces some of the world's priciest coffee--and in the more rolling terrain where Kew Park is located. Johnson and his team set up nylon nets to keep the birds off individual plants (or small clusters). They then compared those plants to the ones birds could reach. Sure enough, the netted-off plants had measurably lower crop yields. At Kew Park, where the impact was most dramatic, Johnson calculated the birds' pest-control value at $125 per acre, or about one-eighth of the total crop value of $1,044 per acre.