Current Conservation Efforts May Not Be Enough for California’s Central Valley Waterbirds

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A new study published in PLOS ONE demonstrates that current conservation planning efforts for waterbird habitat in the Central Valley can likely compensate for habitat loss through the middle of the century.

Clark's Grebe at Thermalito Afterbay, CA
Clark's grebe sitting on a nest at Thermalito Afterbay, California.(Credit: Alex Hartman, U.S. Geological Survey. Public domain.)

However, after 2065, a future with a much warmer, drier climate could reduce waterbird habitat by more than 15 percent, and the combination of these climate projections and reduced water supply could cause even greater habitat losses.

The study addresses uncertainties in climate, the Central Valley landscape, and the water use and delivery system in order to provide useful information for waterbird habitat conservation planning.

Overall, the results indicate that additional wetland restoration and conservation, as well as climate adaptation strategies, may be needed to provide sufficient habitat to support waterbirds in the Central Valley into the future.

“By modeling possible rates of urbanization and other variables to inform future conservation planning activities, we believe that wildlife and habitat management in the valley will be more prepared to face uncertain impacts from human-caused stressors on land and water resources,” said Elliott Matchett, lead author and wildlife biologist with the U.S. Geological Survey Western Ecological Research Center.

During winter, the Central Valley of California is a major resting and refueling area for migratory waterbirds throughout the Pacific Flyway. Birds such as ducks, geese, swans, grebes, cranes, herons, egrets and many shorebird species depend on the valley’s wetlands and agricultural fields (particularly rice and corn) as wintering and migration habitat.

Sandpiper
Sandpipers. Location: Salton Sea, California. (Credit: Doug Barnum, U.S. Geological Survey. Public domain.)

To understand how this habitat may be affected by climate, urban development, water supply management options and wetland restoration, researchers from USGS modeled 17 different scenarios with varying realistic levels of these variables from 2006–2099. This is the first study to evaluate the combined effects of projected conditions of climate, urban development and water management on waterbird habitat in the valley.

The researchers began by adapting a commonly-used integrated water resources model to account for waterbird habitat under the 17 scenarios. These included three climates (two future and one recent historical), low to high urbanization rates, five water management options and two wetland restoration levels. Climate projections represented either a continuous increase in global human population and greenhouse gasses, resulting in a much warmer, drier climate than in recent decades, or global population and emissions with peaks mid-century, declining thereafter, resulting in a warmer climate with relatively little change in precipitation.

The modeling also accounted for slow, moderate and high urbanization rates of agricultural areas. Water supply management options modeled included reduced water supply priorities for certain waterbird habitats and altered water supply management and infrastructure based on the proposed California WaterFix and Suisun Marsh tidal-wetland restoration. The researchers also evaluated current wetland restoration efforts’ ability to offset losses and the effects of no additional wetland restoration.

The project was supported by the California Landscape Conservation Cooperative, California Department of Fish and Wildlife, Delta Waterfowl Foundation, U.S. Fish and Wildlife Service and Central Valley Joint Venture.

Central Valley Water Birds
American White pelican, gulls, sandpipers. Location: Salton Sea, California(Credit: Doug Barnum, U.S. Geological Survey. Public domain.)
Photo of waterbirds feeding at a flooded agricultural field.
Credit Douglas Barnum/USGS. A photo of white-faced ibis and gulls feeding on a flooded agricultural field post-harvest. (Credit: Douglas Barnum, U.S. Geological Survey. Public domain.)