Wind Energy

Wind energy is a fast-growing source of a clean, renewable energy. However, large wind facilities do still have an effect on the ecosystems they're in. A team of researchers led by Edward Arnett studied how wind turbines affect bats. Commercial wind energy development in the U.S. has had a damaging effect on 21 bat species. (That's nearly half of the more than 50 unique species that live in national parks!) All wind energy facilities that have data available have reported bat fatalities. Most of the species of bats that have been affected by wind turbines are migratory, tree-roosting species. These include the hoary bat, the Eastern red bat, and the silver-haired bat. In fact, these three species make up about 70-80% of the reported bat deaths. Read the entire report.

Why do bats fly into turbines?

Every year, migratory bats move from the winter to summer roosts in the spring and then back to the winter roosts in late summer and early fall. Different scientists have put forth several theories why bats collide with wind turbines:

1. Bats may mistake wind turbines for large trees they can roost in.

2. Bats mistake the shiny, reflective surface of turbines for sources of water.

3. Bats don't use echolocation during some periods of migration as they are already familiar with the routes.

4. Bats are simply curious about what the wind turbines are.

In any case, as bats approach the turbines, they're likely looking for a place to rest, simply travelling through the area, or flying after prey. Too often, the blades seriously injure or kill the bats.

Reducing the risk

A 2024 paper in BioScience explores "global green-green dilemma between wind energy production and bat conservation." Some suggested avoidance and mitigations include:

• Avoiding areas of high bat diversity or priority areas for conservation.
• Avoiding forests or woodland edges (choosing an already open landscape).
• Avoiding bat migration and connectivity cooridors.
• Restricting operation of turbines during periods of high bat migration.
• Blade feathering that reduces rotational speed with negligible loss of electricity generation.
• Creating roosting and foraging habitats as compensation for bat habitat loss.

Learn more about what the National Park Service is doing to protect bats and their habitats.

Left to Right: Hoary bat, photo by Paul Cryan; an Eastern red bat at Fire Island National Seashore, NPS photo; researcher holds a silver-haired bat, photo by Paul Cryan.