Can Anyone Build This Bird a Home
Trashing an endangered species' nesting ground was easy, but repairing the damage proved quite another matter
- Susan Milius
- Dec 01, 1992
Can people replace Mother Nature? That's the question behind ecologist Joy Zedler's research in San Diego's Sweetwater Marsh. She's found a great test case in the thigh-high cordgrass stretching along the southeastern curve of San Diego Bay. This broad, flat salt marsh is home to two endangered birds and one endangered plant. This marsh is also where engineers chose to widen Interstate 5, add a giant freeway interchange and dredge a flood-control channel during the 1980s.
Heavy construction is not exactly recommended for endangered species, but the U.S. Fish and Wildlife Service made a deal with the builders: They could wreck part of the marsh if they promised to replace it by building new habitat just like Mother Nature used to make.
But is this possible? In one of the most detailed studies of its kind, Zedler and her graduate students have been looking at five years of restoration work at Sweetwater to see whether the human-made marsh works like a natural one. She speaks quietly but passionately about the importance of the question. Thousands of builders across the country are clinching deals like the Sweetwater swap, wrecking wetlands and promising to rebuild them. But suppose these artificial marshes don't turn out like real ones? Zedler asks the obvious question, "If people don't know enough to restore a wetland, why should they be allowed to destroy it?"
Americans are destroying wetlands faster than an acre every two minutes. The Lower 48 states have already lost half of their original wetlands acreage.
The future does not look good. Americans tend to cluster along the coasts, the zone richest in wetlands. In 1988, 54 percent of the population lived within 50 miles of a coast. That population-129.5 million people—is growing, but the acreage isn't.
Among laws protecting these treasures, the one with the greatest impact has been the Clean Water Act. Its section 404 requires a permit from the Army Corps of Engineers before anyone dredges, fills or otherwise affects a wetland. Before granting that permit, the Corps requires plans to offset unavoidable damage, either by creating wetlands from scratch or by restoring a degraded area. These trades, called mitigations, are boosting the new field of restoration ecology. Its premise is unquestionably lovely—learning to repair the damage people have done to the Earth—but restoration becomes controversial when used as a lever to get permits to do more damage.
This process is particularly contentious in California because the Golden State is developing so fast. The population grew 24 percent between 1981 and 1991. "Everything here is groaning—highways, airports, sewage systems," says Zedler. People have wiped out 91 percent of the state's wetlands. All the creatures specially adapted to these wet zones must crowd into the remaining 9 percent. And that's impossible. Zedler refers to Harvard biologist E.O. Wilson's theory of island biogeography, which predicts that loss of such massive blocks of habitat will kill off 50 percent of these species.
Stakes are high here for conservationists as well as for developers. Buying part of a wetland in order to protect it in this region recently cost one group $1.36 million for 4 acres.
One of the biggest challenges in protecting Sweetwater is saving one of the endangered birds, the light-footed clapper rail. Pairs still nest in cordgrass that escaped destruction by the highway. They slip through the cordgrass, detectable only by their clapping call. Zedler imitates it by smacking her palms together. Occasionally a bird-watcher sights one: a little brown hen of a bird with long legs and a curved beak. These rails were listed as endangered in 1970, and only 257 breeding pairs are known to remain in the country.
Their nesting ground on the eastern edge of the marsh illustrates perfectly how close development looms to coastal marshes. The rails' clapping is hard to hear over 144,000 cars and trucks a day that use Interstate 5 just yards to the east. The nesting ground also has a great view of National City Self Storage and Denny's In-N-Out Burger. Even though this is supposed to be a haven for ground-nesting birds, evening strollers let their dogs run freely. The only rail that many visitors see in Southern California is a stuffed one behind the reception desk at nearby Tijuana estuary reserve. The plaque on the display's base reads "Killed by a cat."
Within sight of this embattled nesting area lies one of two plots that the California Department of Transportation (Caltrans) is trying to enhance as a marsh to make up for habitat it ruined during the highway construction. When Caltrans first started on the project, mitigation faltered. The Sierra Club and the League for Coastal Protection sued in 1986 and won a spectacular victory. The decision set off a chain of negotiations that protected more than 300 acres of marshland and imposed tough new standards on Caltrans' restoration project.
For example, just planting some cord-grass is not enough; now Caltrans must show that cordgrass has covered 90 percent of 968.4-square-foot patches for at least two years.
Caltrans biologists knew this job would be difficult. "It's the stuff of nightmares," says Pam Beare, the Cal-trans ecologist supervising restoration at Sweetwater Marsh. Caltrans shells out considerable amounts of money—the most recent project cost about $500,000—hoping that an unknown natural factor won't spoil the effort.
Zedler has followed the restoration closely, partly for research and partly as a monitor funded by Caltrans. She has seen a lot of disasters caused by previously unknown natural factors.
Caltrans planted eight islands of cordgrass, each about the size of a suburban yard, to try to create a new nesting area. After five years, Zedler reports that no rails have nested in the artificial islands.
She puzzled for months over why the islands were a flop and thinks she now has the answer, a factor no one dreamed of: The human-planted cordgrass is too short.
Rails need tall grass because their nests, thick patties of mashed cordgrass, float up as the tide rises. The cordgrass must be taller than the tide or water will sweep away the nests.
Why the cordgrass is stunted remains confusing. There's not enough nitrogen, but just adding fertilizer hasn't helped.
Sweetwater's rare plant, salt marsh bird's beak, has also baffled Caltrans. An ankle-high member of the snapdragon family, bird's beak has spiky purple leaves and pink blooms like teardrops. Declared endangered in 1978, it now grows in fewer than ten sites along the Pacific Coast. One of Joy Zedler's students, Brian Fink, spent more than a year analyzing the plant's requirements. Using his information, Caltrans planted a patch, which bloomed successfully—but then, withered unpollinated. Caltrans had not provided the right conditions for pollinators.
Scientists do not know what those conditions are, or even what species the pollinator is. Zedler, however, thinks it's probably some kind of solitary ground-nesting bee. Caltrans will have to find out, though, because creating a fully functioning marsh means finding all the parts.
Insects have more than once tripped up marsh restorers in San Diego Bay.
Zedler describes an island of cordgrass that was planted in the bay in the mid-1970s. The cordgrass was supposed to make up for habitat chewed away in building a boat basin. "It looked really good," Zedler says. At first. Then a massive attack of tiny scale insects left the cordgrass tattered and ailing.
Now she knows that in natural salt marshes a tiny Coleomegilla beetle with heart-shaped spots roves cordgrass, preying on scale insects and keeping populations from exploding. The beetle doesn't swim, so it never established a thriving colony on the island. The human island builders, of course, hadn't realized the beetle was important enough to introduce.
There's a lot people don't know about insects of salt marshes. Zedler remembers tugging apart some cordgrass her students had planted and finding fly pupae. As is routine, she sent the insects to the U.S. Department of Agriculture for identification. The news came back that the flies were a species new to science.
Caltrans continues to work on the site, researching and replanting. Zedler continues to monitor, but concludes after five years the restored marsh is "not functionally equivalent" to the real one.
Ask her the big question—can people imitate nature—and she says, "Our research shows we don't know how to do it yet." She acknowledges that "there may be places where wetland mitigation can work, but they're not in Southern California."
The National Research Council concluded much the same thing, thanks in part to her influence. In December 1991, the council called for a big national effort to save and restore wetlands. Yet the council cautioned that restoration is a "trial-and-error process." Fixing what's already broken is noble, but ruining a good marsh is another matter. "Wetland restoration should not be used as a way to offset or justify the destruction of other wetlands," says the report. As Zedler puts it, "Just say no to development in wetlands."