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.
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