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Wind farms – new age predators

How is a wind mill like a bird of prey?

GBSNP Varma

doi:10.1038/nindia.2018.156 Published online 30 November 2018

The researchers found that wind farm areas had fewer predatory birds and higher number of lizards than non-wind farm areas.

© Maria Thaker

Ecological scientists studying the effect of wind farms on local ecosystems say that the turbines may have the same effect that a predator has on multiple levels of the food chain1.

Wind turbines – known to kill birds and bats from direct impacts and to obstruct bird migration routes – may also affect terrestrial animals as their construction modifies the habitat. Besides noise and visual impact, wind turbines may also attract predators.

“Just that in this case, the top predator in the ecosystem is the wind farm itself,” says Maria Thaker, lead researcher from the Centre for Ecological Sciences at the Indian Institute of Science, Bangalore.

Thaker and colleagues conducted experiments in areas with and without wind turbines but having similar geography and vegetation in the biodiversity hotspot of Western Ghats of India.

They first estimated the density of predatory birds such as raptors (of the Buteo, Butastur and Elanus species) and the frequency at which they attacked their prey – primarily the lizard Sarada superba. The researchers stood on elevated spots on plateaus and counted the number of birds and the number of times they dived to the ground to hunt.They then walked at least one kilometre (transect) in straight lines in each area counting the number of lizards within every 20 metres.

As expected, they found fewer predatory birds and lower bird activity in areas with wind farms, resulting in higher number of lizards.

“What surprised us was that the effect of wind turbines on lizards went beyond just their numbers. It also influenced their behaviour, physiology and morphology,” says Thaker.

In stressful situations, humans and most other vertebrates including lizards, release glucocorticoid hormones from their adrenal glands. An optimum level of these hormones maintains internal equilibrium or homeostasis. An acute spike of glucocorticoids is necessary to react to a stressful event.

Thaker and colleagues found that lizards in areas with or without wind turbines had similar baseline levels of glucocorticoids, which means they were maintaining their body functions similarly.

“But when challenged with an additional stressor like a predator attack, the ones in areas with wind turbines produced lower concentrations of this hormone, suggesting that their physiology has shifted – they perceive their environment as less dangerous and no longer react with high hormone levels,” she said.

However, when predation risk is high – for instance, in areas without wind turbines where raptors regularly hunt – the lizards increased their stress hormone response and were behaviourally wary and vigilant.

Wind farms also had an effect on the lizards’ secondary sexual characteristics. Male fan-throated lizards, which use rich blue, black and orange dewlaps to communicate with other males and females, showed less saturated and less bright coloursin areas with wind turbines. The researchers say this may be due to higher competition and limited resources.

The network of interactions in any ecosystem is complex and even a small change can bring about a cascade of effects, many quite unpredictable, says Milind Watve, a professor of biology at Indian Institute of Science Education and Research (IISER) Pune.

Whether wind farms are good or bad “is our interpretation”, Watve says, and should be based on wider studies that allow us to see as many sides of a change as possible.

Thaker’s co-worker Amod Zambre, who is presently in the department of ecology, evolution, and behavior at University of Minnesota in USA, says though wind farms area cleaner alternative to fossil fuels, their ecological consequences have been greatly underestimated.

“There’s a strong need for an ecosystem-wide view when aligning green-energy goals with environment protection.”


References

1. Thaker, M. et al. Wind farms have cascading impacts on ecosystems across trophic levels. Nature Ecology & Evolution (2018) doi: 10.1038/s41559-018-0707-z