Up in the Air
Climate Change Compounds Threats to Birds
Each spring the red knot, a shorebird with a rust-colored belly, transects the globe, flying from the southern tip of South America to the northern reaches of the Arctic. Midway through this flight, the birds lay over at the Delaware Bay, where they refuel by gorging on tens of thousands of horseshoe crab eggs.
In the 1990s, this age-old migration ran into trouble when red knot populations began crashing. Evidence pointed largely to shellfish overharvesting, but recent observations by birders and researchers have revealed an additional threat from climate change: Warmer temperatures are prompting the horseshoe crabs to lay their eggs earlier in the year, meaning less food for the migratory birds when they arrive at the bay.
These findings and other research about the impact of climate change on birds are the focus of the 2010 State of the Birds report, issued by scientists from the Cornell Lab of Ornithology, The Nature Conservancy, federal agencies and other organizations. The group’s 2009 report found that roughly one-third of bird species in the United States are endangered or are in serious decline.
The 2010 report examines the vulnerability of birds to future threats, says Ken Rosenberg, director of conservation science at the Cornell Lab of Ornithology.
The report finds that birds most imperiled by past changes such as habitat loss—particularly seabirds, shorebirds and island birds (especially those in Hawaii)—are also the species most vulnerable to the impacts of climate change. For example, the scientists warn that rising sea levels will destroy key habitat for many marine birds.
On a positive note, the report suggests that many forest and grassland birds have already begun to adapt to climate shifts by relocating, in direction or elevation, to habitats more to their liking.
David Mehlman, director of the Conservancy’s migratory bird program, says the report’s analyses will help identify emerging risks to birds so that proactive steps can be taken to curb threats. “We need not only to protect where biodiversity is now, but where we think it’s going in the future,” he says.
In coordination with the report, the U.S. Department of the Interior is launching a network to pool climate research and to promote conservation strategies for threatened birds. This collaboration, Rosenberg says, “takes bird conservation to a new level.”
— Joshua Zaffos