Solar farms could come with a pollinator bonus

DAILY SCIENCE

Solar farms could come with a pollinator bonus

New research shows how habitat-friendly solar energy can safeguard insect populations—and improve pollination services on adjacent farms.
January 24, 2024

Converting the world to renewable energy such as solar might be a linchpin to tackling climate change, but it comes with a mighty big footprint.

In the U.S. alone, solar panels could cover land equal to Maryland and Delaware combined by 2050 if the country meets climate and renewable electricity goals.

That makes it a priority to minimize the downsides of oceans of solar panels sprawling across the landscape. For instance, what if prime farmland or ecologically important habitat becomes sought after for solar farms? By one estimate, as much as 80% of future solar sites could be built on agricultural land.

Now, scientists suggest that part of the solution could come in the form of an oddly-named strategy: agrivoltaics.

The term might conjure images of a Frankenstein-like use of electricity to spur plants to grow faster. It actually refers to the possibility of doing double-duty with land by inserting agricultural activities such as growing alfalfa or grazing sheep amongst the rows of shiny black panels. Another possibility is turning neglected, low-yield farmland into a combination energy factory and wildlife habitat.

To see if the promise of a solar farm pared with a critter haven could bear fruit, scientists from the Department of Energy’s Argonne National Laboratory in Illinois and the National Renewable Energy Laboratory in Colorado converged on southern Minnesota to count bugs.

In 2017, two different solar installations in the middle of Minnesota’s farm country were built on 76 acres of land that had been farmed with row crops for decades. Much of the land beneath the panels was dosed with the Glyphosate herbicide to kill weeds, then seeded with 66 different species of native grasses and flowers. A small sub-section of the land got a bonus of another five dozen plant species.

 

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The following year, researchers began systematically scouring the areas planted with the extra species to tabulate all the insects they could find. Through 2022, they visited the same strips of grass and flowers four times each summer during peak flower season, tracking the number and types of insects to see if bugs took to the panel-topped landscape.

Within a few years, the area was teeming with six-legged creatures. The total number of insects had tripled. By the end of five years, the population of native bees such as bumble bees and little sweat bees had soared to more than 20 times their initial tiny numbers, the scientists reported in December in the journal Environmental Research.

“This research highlights the relatively rapid insect community responses to habitat restoration at solar energy sites,” said Lee Walston, a landscape ecologist at Argonne who led the study. 

At some level, it’s not a surprise that insect numbers rose as fields beneath the panels turned from land nuked by herbicides to one filled with wildflowers. It’s not clear how close the final results matched pockets of more natural habitat in the surrounding area. For instance, the researchers didn’t check to see how the insect numbers on the solar farm compared to nearby farmland set aside under the federal government’s Conservation Reserve Program. But they noted that experiments elsewhere showed that insect numbers on restored land could match nearby grasslands within just four years. The rise in insect diversity in those experiments was similar to what they witnessed.

The bug boom at these solar sites appeared to have spillover benefits. When they inspected soy blossoms at surrounding soybean farms, the ones near the panels had higher numbers of bees and other pollinators such as moths than did plants in the center of the bean fields. This pollinator bonus was comparable to the benefits the researchers found when they checked soy plants growing next to conservation reserve lands.

​“It demonstrates, if properly sited, habitat-friendly solar energy can be a feasible way to safeguard insect populations and can improve the pollination services in adjacent agricultural fields,” Walston said.

The findings come at a time when many insect species, including pollinators, are declining around the world. The spread of high-intensity farming and pesticides have been fingered as major culprits. While solar farms are yet another industrial footprint on the land, when it comes to insects, perhaps they could have a lighter touch.

Walston, et. al. “If you build it, will they come? Insect community responses to habitat establishment at solar energy facilities in Minnesota, USA.” Environmental Research. Dec. 18, 2023.

Image: AgriSolar Clearinghouse

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