Wind farms are popping up all over the world. In the U.S. alone wind power capacity has tripled over the last decade. Although this trend is good news for efforts to curtail emissions and climate change, a growing body of research suggests wind turbines disturb their local environment in a significant way. Scientists have documented, for example, turbines killing hundreds of thousands of birds and bats.
Now a new study has found wind energy also influences ecosystems indirectly, via changes that trickle down through the food web: Like tigers, great white sharks and humans, wind turbines can function as apex predators.
But researchers stress that even though wind energy has ecological impacts, we should still use it. After all, fossil fuels upset the environment in a much more profound way. Rather than criticizing wind power the scientists involved say their work is intended to help people make better-informed decisions about how and where they use clean energy.
Wind farms have operated in the Western Ghats mountain range, a biodiversity hotspot in India, for about two decades. The location was a perfect place for researcher Maria Thaker and her colleagues to study how turbines affect the local ecosystem. Their work, published last week in Nature Ecology & Evolution, found birds were four times scarcer and hunted food less in zones with wind farms than in those without. But this was not because birds were flying into turbine blades and dying, the researchers say. “We could see the birds come up to the edge of the wind farm and then fly away,” says Thaker, a professor of ecology at the Indian Institute of Science’s Center for Ecological Sciences. “It was straight-up avoidance.”
Thaker and her team then assessed the population of a certain lizard species the birds typically prey on. They counted the lizards, took blood samples to measure stress levels and analyzed body condition and coloration. (Males have a brightly colored flap of skin beneath their jaws, which they use for sexual communication). The scientists also recorded the lizards’ sensitivity to predators—how closely the researchers could approach them without the animals running away.
Not surprisingly, the researchers found a greater lizard population in areas with wind turbines, because there were fewer birds. “We fully expected that when you have a loss of top predators, the density of prey will increase,” Thaker says. These lizards were also less wary of predators and had lower stress levels than their counterparts outside the range of the turbines.
The rest of their results, however, were unexpected. Even though lizards living with the turbines were under less pressure from predators, they were skinnier and less colorful than members of their species living elsewhere. This may sound counterintuitive, but Thaker says it makes sense ecologically. “The high competition for food meant that the quality of each individual was actually reduced,” she notes. “That’s the nuance of what happens when you remove the top predator.”
Beyond how wind turbines affect this lizard species, the study has a bigger point: It indicates wind farms can create a cascade of unintended effects within an ecosystem by essentially acting like top predators. “This man-made structure has removed a layer in the food web. That’s what a top predator does—it takes out the layer below it,” Thaker says. “By taking out the layer below it, the layer below that one is released from pressure.”