Stemming the Tide of Shorebird Losses
With migrations that can span thousands of miles, Pacific shorebirds are among nature's most amazing aerialists. But without crucial stopover habitat along their way, they could be doomed.
On a subdued April afternoon in Nanpu, an industrial town on China’s Bohai Bay, the air is salty and acidic from the saltpans, oil refineries, and steel and soda factories that cram along the coast. The mudflat slowly emerges from the receding tide, its soft sediment shimmering like a gigantic tin roof. Large flocks of shorebirds—bar-tailed godwits, dunlins, red knots, great knots, curlew sandpipers, whimbrels, sanderlings, and red-necked stints—feed frenetically at the water’s edge. With their highly specialized bills, they quickly dig out a feast of worms, clams, and crabs from the seemingly lifeless tidal flats.
Some of the birds are already in their bright-colored breeding plumage, while others still have most of their winter feathers. Their incessant pecking hints at a sense of urgency. “They have no time to waste,” says Yang Hongyan, a postdoctoral researcher at Beijing Forestry University. Indeed, these seemingly delicate creatures are among the 5 million shorebirds of 60 species—about half of the world’s shorebird species—that stream from Australia and New Zealand every spring over featureless ocean toward their breeding grounds, some going as far north as the Arctic, including Alaska. The route constitutes one of the world’s most important flyways, the East Asian-Australasian Flyway (EAAF).
Before setting out on the final leg to the Arctic, most of the birds stop to rest and refuel along the shorelines of the Yellow Sea—a marginal sea of the Pacific Ocean enclosed by northeastern China and the Korean Peninsula—including Bohai Bay. They fatten up considerably during their short stay here, in some cases doubling their typical body weight, in order to reach northern Alaska or Siberia and still have plenty of reserves upon arrival, when feeding conditions may be poor. “The Yellow Sea is like a gas station for these long-distance migrants,” says Nils Warnock, executive director of Audubon Alaska. “If they can’t fill the tank, they will end up in the middle of the ocean.”
But with a strong push for economic growth and infrastructure development, China and South Korea are rushing to convert the Yellow Sea’s mudflats to ports, industrial complexes, aquaculture enclosures, and residences. The mudflats “have been a critical staging site for thousands of years but are now disappearing fast,” says Theunis Piersma, an evolutionary biologist at the University of Groningen and the Royal Netherlands Institute for Sea Research. Yellow Sea tidal flats have declined by 65 percent in the past 50 years. This “has made the EAAF one of the most threatened flyways in the world,” says Doug Watkins, manager of Wetlands International-Oceania and chair of the Yellow Sea Ecoregion Task Force of the EAAF Partnership, a conservation group that promotes international cooperation in protecting shorebirds and their habitats on the flyway.
Twenty-four shorebird species that use the flyway are heading toward extinction, with many others facing exceptionally rapid losses, sometimes as high as 5 percent to 9 percent a year, according to a report released last October by the International Union for Conservation of Nature (IUCN). The worst hit are the long-distance, Arctic-breeding migrants such as the red knot and the spoon-billed sandpiper; the latter, declining at a rate of 26 percent a year and with fewer than 200 breeding pairs in the wild, is listed by the IUCN as critically endangered. These rates are among the highest of any on the planet, the report says. And all species identified as declining rely on the Yellow Sea shoreline during migration.
It’s extremely challenging to make an airtight case that the marked reduction of mudflats in East Asia, especially on the Yellow Sea, is responsible for the rapid decline in flyway populations of such species as the red knot and spoon-billed sandpiper. It’s also hard to persuade policy makers to step up protection of the remaining key stopover habitat. This is the mission that Piersma—a world-renowned expert on the red knot and the namesake of one of its subspecies, Calidris canutus piersmai—and his team, including Yang, have set out to accomplish.
In the past couple of years, national newspapers in China have started covering the issue, running stories on the importance of tidal flats and featuring senior politicians speaking out against massive reclamation projects. With the situation so critical, scientists and conservation groups are campaigning hard to save the remaining vital staging sites on the Yellow Sea. “We have to act now,” says Zhijun Ma, an ornithologist at Fudan University in Shanghai. “Many of these bird populations will collapse in the foreseeable future if the rate of land reclamation does not slow down soon.”