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Study: Climate warming threatens birds on wildlife refuges

climate warming
Blackburnian Warbler is currently found at 32 national wildlife refuges in the continental United States during the summer. New research projects that when global surface temperatures reach 2°C above pre-industrial levels, the songbird will be lost entirely from the refuge system. Photo by Ray Hennessy/Shutterstock

Earth’s global surface temperature is currently about 1.1 degrees Celsius warmer than it was in the late 1800s, and scientists project it will continue to climb in coming decades. If carbon emissions remain at their current levels, we can expect to surpass 2°C in warming around 2052, according to analysts at CarbonBrief.

Since the early 1900s, the United States has established more than 560 national wildlife refuges on more than 150 million acres, offering protections for birds, mammals, plants, insects, fish, and other wildlife. Refuges provide safe havens from development, but climate warming poses greater challenges.

A team of researchers from Audubon and the U.S. Fish and Wildlife Service recently analyzed how bird communities would change on national wildlife refuges if and when we reach 2°C in warming. Their study appeared in the August 2022 issue of Ornithological Applications.

Approximately a quarter of bird species observed on refuges may be different by the 2050s, the authors say. Refuges may see a slight net loss of species in summer (from 109.0 to 102.0 species per refuge) and a net gain in winter (from 97.1 to 118.5 species per refuge). Some species may be lost from the entire refuge system, including Emperor Goose, Tundra Swan, and Black-throated Blue and Blackburnian Warblers.

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Other species are predicted to disappear from the current refuge system in summer, but due to shifting winter ranges, the birds are expected to be found at more refuges during the colder months than they are now. Under a 2°C warming scenario, Clay-colored Sparrow may disappear from the 100 refuges it is currently found at in summer; in winter, the sparrow would occur on 25 refuges, whereas it currently winters at five refuges.

Particularly vulnerable species to climate warming may benefit in the near term from targeted management aimed at preventing species loss. “The refuge system has the capacity to mitigate loss for some of the most climate-vulnerable species in a Resist-Adapt-Direct framework,” the authors say. “For example, managers can help the Clay-colored Sparrow by providing more grassland habitat via crop set-aside programs. The Nelson’s Sparrow will likely benefit from resisting coastal wetland development. Regions of greater species turnover (i.e., at northern latitudes) might be prioritized for strategic additions of new refuges, ensuring proportions of habitats protected reflect the need.”

A version of this article appears in the November/December 2022 issue of BirdWatching magazine, in “Birding Briefs.”

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