Stopover wetlands in the Sacramento Valley have shrunk dramatically
Date: March 27, 2017
Source: Duke University
Drought and reduced seasonal flooding of wetlands and farm fields threaten a globally important stopover site for tens of thousands of migratory shorebirds in California's Sacramento Valley, a new Duke University-led study shows.
The researchers' analysis of historical biweekly NASA Landsat satellite images of the valley reveals that flooded habitat near the peak time of spring migration has shrunk by more than twice the size of Washington, D.C. over the last 30 years.
"On average, we're losing an area about four times the size of Central Park each year, during a critical window of time in late March," said Danica Schaffer-Smith, a doctoral student at Duke's Nicholas School of the Environment, who conducted the study with researchers from the nonprofit Point Blue Conservation Science.
More than half of all shorebird species in the Western hemisphere are now in decline, Schaffer-Smith noted.
The Sacramento Valley site is an internationally important resting and refueling stop for tens of thousands of these wetland-dependent birds traveling along the Pacific Flyway. Some of these species migrate thousands of miles from Argentina to Alaska and back again each year.
"The fact that these highly mobile species are increasingly struggling to find flooded habitat on their migrations is an indicator that our freshwater wetland systems are in trouble," Schaffer-Smith said. "Freshwater is essential for all life. Many other species rely on these same habitats, too."
The Sacramento Valley once supported a huge network of wetlands connected to the San Francisco Bay Delta, but more than 90 percent of them have been drained for agriculture. Analysis of recent satellite images by Schaffer-Smith and her team shows that open water covers just three percent of the landscape during peak migration in April, when the birds urgently need flooded habitat to rest and feed.