Solar farms: how they affect biodiversity and what it means for our ecosystem

With the planet continuing to warm, the need for renewable energy is becoming increasingly urgent. Almost half of the UK’s electricity is already generated from renewable sources. And solar power makes up one-fifth of installed energy capacity from 2019.

Solar farms are now an amazing feature of the British landscape. But despite their growth, we still know little about how solar farms affect biodiversity.

This was the focus of a recent study I co-authored with colleagues at the University of Bristol. We found that bat activity was reduced on solar farms compared to neighboring sites without solar panels.

This finding is cause for concern. Bats are apex predators of nocturnal insects and are sensitive to changes in their habitats, so they are important indicators of ecosystem health. Bats also provide valuable services such as suppressing pest populations.

Nevertheless, our results should not discourage the transition to renewable energy.

They should help develop strategies that not only promote bat activity but also support the necessary expansion of clean energy sources.

Reduced activity

We measured bat activity by recording their ultrasonic echolocation calls on bat detectors. Many bat species have characteristic echolocation calls, so in many cases we were able to identify call sequences for each species. Some species have similar calls, so we combined them into species groups.

We placed bat detectors in a field with solar panels and in a similar neighboring field without solar panels (control plot). Fields were matched for size, land use and boundary features (e.g. presence of similar hedgerows) as far as possible. The only significant difference was the presence or absence of solar panels.

We monitored bat activity at 19 pairs of these plots, each week, observing bat activity in the center of the fields and along field boundaries. Field boundaries are used by bats for navigation and foraging.

Six of the eight bat species or groups studied were less active in fields with solar panels compared to fields without them.

Common pipistrelles, which accounted for nearly half of all bat activity, showed a 40 percent decrease at the edges of fields with solar panels and an 86 percent decrease in their center. Other bat species or groups, such as soprano pipistrelli, noctules, serotines, myotis bats, and long-eared bats, also experienced declines in their activity.

Overall bat activity was nearly halved at the edges of the solar panel fields compared to control plots. And in the center of the solar panel fields, bat activity dropped by two-thirds.

Why do bats avoid solar farms?

The conflict between clean energy production and biodiversity is not limited to solar farms; it is also a problem on wind farms.

Large numbers of bats die from collisions with wind turbine blades. In 2012, one scientist estimated that about 888,000 bats may have been killed at wind energy facilities in the United States.

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