The Central Valley in California was once one of North America’s most productive wildlife habitats, a 450-mile-long expanse marbled with meandering streams and lush wetlands that provided an ideal stop for migratory shorebirds on their annual journeys from South America and Mexico to the Arctic and back.
Farmers and engineers have long since tamed the valley. Of the wetlands that existed before the valley was settled, about 95 per cent are gone, and the number of migratory birds has declined drastically.
But now an unusual alliance of conservationists, bird watchers and farmers have joined in an innovative plan to restore essential habitat for the migrating birds.
The programme, called BirdReturns, starts with data from eBird, the pioneering citizen science project that asks birders to record sightings on a smartphone app and send the information to the Cornell Lab of Ornithology in upstate New York.
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By crunching the data, eBird can generate maps showing where virtually every species congregates in the remaining wetlands. Then, by overlaying those maps on aerial views of existing surface water, it can determine where the birds’ need for habitat is greatest.
The BirdReturns programme, financed by the Nature Conservancy, then pays rice farmers in the birds’ flight path to keep their fields flooded as migrating flocks arrive. The prices are determined by reverse auction, in which farmers bid for leases and the lowest bidder wins.
The project’s first season ended last month. Researchers said all of the birds whose numbers they hoped to improve were seen on “pop up” wetlands — a temporary steppingstone for the birds’ journey north. This happened when the field would have ordinarily been drained, an indication that the approach was working. The fields will be flooded again in the fall for the birds’ return journey. Eventually, using this and other approaches, the conservationists at BirdReturns hope to increase the number of shorebirds that stop in the Central Valley to 400,000, from current levels of 170,000.
BirdReturns is an example of the growing movement called reconciliation ecology, in which ecosystems dominated by humans are managed to increase biodiversity.
It could also be an exportable solution. Agriculture creates some of the world’s most serious ecological problems. If BirdReturns proves itself, it could be an inexpensive model for adjusting agricultural landscapes to mesh with the needs of wildlife.
Migration takes a great deal of energy and is the riskiest thing birds do. Each January, about 20 species of shorebirds and several dozen species of wading birds start dropping into the Central Valley on their arduous journey north. The shorebirds — among them dunlins, snipes, and marbled godwits — zoom into wetlands, and wade on stiltlike legs through a few inches of water or across glistening mud flats to ferret out worms and insects.
Until now, one of the biggest problems has been that in February, at the peak of migration, rice farmers are letting their fields dry out in preparation for planting. “When they need it most, there’s less and less habitat,” said Mark Reynolds, a Nature Conservancy scientist who helped design the programme.
In 2012, Reynolds and Brian Sullivan, the eBird project leader for the Cornell Lab of Ornithology, got the idea of using the sighting data to find out where the shorebirds go. They overlaid the data on maps of water availability to determine where the needs for wetlands were greatest.
When eBird data show that a migration is underway, rice growers who have entered low bids open their irrigation ditches to provide just the right amount of flooding. That results in the pop-up wetlands.
In this first year, 10,000 acres (out of 500,000 devoted to rice farming in the Central Valley) owned by 40 farmers were flooded for four, six or eight weeks. Even so, the programme can require some careful calibration. “If we put our water on late, the fields might not dry out” in time for planting, said Doug Thomas, a farmer who took part in the programme this year.
“Migratory birds are a daunting challenge,” Reynolds said. “It’s a hemispherical scale and every species has a different life history.” But he added that if BirdReturns’ encouraging early results prove out, “you could create habitat all along the flyway”.
Crawling into your head