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Importantly, those population-level effects often extended far beyond the region where the fatalities occur. Although existing science has shown that renewable energy production sometimes kills individual birds, this study is the first to assess impacts to larger-scale populations.

“The results of this research matter because nearly all environmental impact assessments conducted at renewable energy facilities focus on local subpopulations to estimate consequences of fatalities,” said Tara Conkling, U.S. Geological Survey Wildlife Biologist.

The authors estimated vulnerability of 23 priority species from bird fatalities at wind and solar energy facilities in California. Priority species were identified by biologists, managers, and conservationists with expertise in wind and solar-wildlife issues in California. The scientists used a five-step framework, combining data on known population sizes and natural history, biochemical analyses to identify origins of dead birds, and population models to estimate vulnerability on these 23 species.

Of the 23 species studied, 48% were estimated to be highly or moderately vulnerable to effects from fatalities at renewable energy facilities. Furthermore, for some species only local populations were vulnerable, for other species vulnerable populations originated far from California. Most vulnerable species came from subpopulations that spanned a narrow geographic range or were not abundant within the local area. Likewise, some vulnerable species were from habitats similar to where renewable energy was found. However, in the case of solar energy, populations of nocturnal migrant species were most vulnerable, despite not typically being associated with deserts where studied solar facilities were located.

“This study shows that because renewable energy may affect both local and nonlocal subpopulations, cumulative effects of renewable energy are likely more extensive than previously understood, especially for migratory species,” said Conkling. “In the case of renewable energy, decisions about facility placement on the landscape, as well as actions to minimize and mitigate the effects of fatalities, could be more effective if managers consider both local and nonlocal population impacts, and consider habitat far from where the facility is located.”