Study estimates 18.7 million bat deaths at US wind turbines

What you need to know

• Researchers combined 499 post-construction monitoring reports in a multispecies Bayesian model. It estimated fatalities for ten bat species across the contiguous United States over the 44-year period. 13
• The USGS reports that estimated annual fatalities exceeded 1.5 million from 2021. Hoary bats, eastern red bats and silver-haired bats were among the species with the highest estimated cumulative losses. 24
• Higher fatality rates were associated with factors including proximity to rivers, lower turbine ground clearance and larger rotor-swept areas. These are modelled associations, not evidence that any single factor causes deaths. 124
• The findings can inform risk-based siting and turbine curtailment, measures that may reduce some fatalities. The reporting does not show that they have yet led to a nationwide reduction. 124
• The study's estimate concerns its ten-species model. One news report gives a different species count, but the study record and USGS data release specify ten species for the modelled estimates. 135

Why this matters

The estimate points to a substantial source of bat mortality associated with wind energy, while the uneven distribution of risk suggests that location and operating conditions may matter. Knowing whether this pressure affects population trends is important for judging its conservation significance. 124

What happens next

The sources identify updated population-status and trend assessments, better monitoring and evaluation of mitigation as important next steps. They do not report a nationwide intervention or its outcomes. 123

What we know

• The study modelled fatalities across the contiguous United States from 1981 to 2024. 13
• Its cumulative estimate was approximately 18.7 million deaths across ten modelled bat species. 13
• Estimated risk varied by species and location, and was associated with several turbine and landscape factors. 124
• The estimate was derived from monitoring reports and a statistical model, rather than a direct count of every fatality. 13

What we don't know

• The sources do not establish how the estimated deaths have affected population trends in the ten modelled species. 12
• The effect of variation in monitoring methods and missing data on the estimate and its uncertainty remains unclear. 3
• The reporting does not determine which siting or curtailment measures would be most effective across different species and locations. 124
• The sources do not show what outcomes would follow from implementing those measures at a wider scale. 124

Read the reporting

This WildNews briefing synthesises and summarises reporting from the sources below. WildNews did not produce the original reporting. Learn more about how we use AI