"Walking Wetlands" Help Declining Birds, Boost Crops
for National Geographic News
|August 18, 2009|
The request struck Dave Hedlin, a farmer in Washington's fertile Skagit Valley, as particularly odd: Conservationists wanted him to voluntarily flood his fields.
"Most of us have spent our entire lifetimes trying to keep water off the land," said Hedlin, whose farmlands are nestled among inlets, bays, and estuaries in the shadow of the snowcapped Mount Baker volcano.
But he decided to take part in a pilot project run by the Nature Conservancy, which temporarily floods agricultural fields to restore shorebird habitat. (See photos.)
The flooding would be part of his farm's regular crop rotation, and in theory would pay for itself by filling the fields with natural fertilizer, drowning disease-causing bacteria in soil, and boosting crop yields.
In turn, the wetlands would again become a rest and refueling station for migratory shorebirds between their Arctic breeding grounds and southern winter retreats.
Of the 53 shorebirds that breed in North America, more than half are at grave risk, according to the U.S. Shorebird Conservation Plan, a program run by a coalition of public and private organizations.
(Related: "World's Wading Birds Are Vanishing Fast, Experts Warn.")
After three years, early results suggest that the project is working: Fifteen shorebird species have returned to the restored wetlands.
So far, three participating farmers have been happy with the experiment, including Hedlin, who said that he has not suffered financially.
Before the valley was converted to agriculture at the beginning of the 20th century, its wetlands had teemed with crustaceans, fish, and bugs.
But since the wetlands became farmlands, most of the 50,000-some birds that visit each year feed in the nearby estuaries instead.
"We've totally changed this landscape," said Julie Morse, an ecologist with the Nature Conservancy in Mount Vernon, also in the Skagit Valley.
"It used to be tidally influenced, but now it is very much a diked system, and there are just not the wetlands that there used to be."
The Skagit Valley project is modeled after a decade-old "walking wetlands" concept in the Klamath Basin of southern Oregon and northern California, where farmland within a wildlife refuge is placed on a wetland rotation.
Laura Payne, a wildlife ecologist based at the University of Washington in Seattle, called the project an innovative collaboration between farmers and conservationists.
"This idea has the potential for wide application, and I think it is absolutely relevant," Payne said.
If the project is successful, the Nature Conservancy plans to replicate the walking wetlands concept on farms throughout migratory-shorebird flyways, which extend from the Arctic to Central and South America.
(Read about more sustainable-agriculture projects here.)
"Loss of wetlands in coastal areas for farming has happened all around the world, so it could be implemented anywhere," the Nature Conservancy's Morse said.
The three Skagit Valley farmers, including Hedlin, who signed up to participate in the project have also helped shape it.
"They asked for advice first off, instead of telling us what they wanted to do," Hedlin said.
The team hatched a plan to flood select fields with a thin sheet of water—no more than four inches (ten centimeters) deep, an ideal level for shorebirds—for three years. The plots stayed flooded for the entire experiment.
Doing so required the farmers to build berms to prevent water from flooding their neighbors' land.
Preliminary results of the first three years suggest a partial success.
In the first year 15 species of shorebirds used the flooded fields, and only 2 shorebird species used the grazed and greenchop fields—pointing to a possible ecological benefit of the flooded parcels.
The Nature Conservancy team has no data on how many shorebird species historically visited the wetlands, Morse said, and only about three species had been spotted after the conversion to agriculture. So the team was pleased to see 15 species return, Morse said.
But by the second year, cattails in the flooded fields were more than 15 feet (5 meters) tall, which proved too difficult for the shorebirds to navigate. That year only eight shorebird species visited the fields.
"It is pretty amazing that you let nature go and it [returns to a native state] that quickly," the Nature Conservancy's Morse said.
The conservationists are now considering plans to actively manage the flooded fields to keep them primed for shorebirds.
Farmers also saw a financial benefit: Nitrogen levels in the flooded fields increased on average by 50 pounds (23 kilograms) per acre (0.4 hectare), which means that farmers may have spent less money on fertilizer.
Hedlin, the farmer, said he used the three-year flood to transition his field to organic, as fields have to sit fallow for three years for organic certification.
"We had a positive experience and didn't go backward financially," he said.
The Nature Conservancy's Morse is now comparing how much money is gained on a grazed field versus a greenchop field versus a flooded field.
"The big thing that we are doing that they haven't done in the Klamath is really trying to quantify how much value it provides to the farmers and how much [shorebird] habitat it provides," Morse said.
"And we're comparing the ecological benefits of those three habitats as well," she added.
Links in a Chain
Mark Colwell, a wildlife biologist at Humboldt State University in Arcata, California, praised the project's innovation.
But helping migratory shorebirds bounce back is not easy, Colwell said.
Habitats such as the Skagit Valley and the Klamath Basin can be thought of as links in a chain along the migratory-shorebird flyway.
"You can do stuff at a series of links in the chain up and down the flyway, but if at one site there's a serious problem there, well, the whole population could plummet."
Nevertheless, Colwell added, enough of these projects spread out along the flyway could help birds find enough food over the courses of their annual migrations.
(Related: "Alaska Bird Makes Longest Nonstop Flight Ever Measured."
The University of Washington's Payne noted that migratory shorebirds are opportunistic, particularly along inland flyways where wetland conditions are unpredictable.
They know a good habitat when they see one, such as a normally dry area that floods in a particularly wet year, Payne said.
Alternative habitats such as temporarily flooded fields, she said, "suits this group of species."
|© 1996-2008 National Geographic Society. All rights reserved.|