Isaac Ogle strides through a field filled with waist-high broomsedge bluestem, a scruffy native grass, into a utility solar array. He’s founder of Comprehensive Botanical Services, which specializes in solar grounds maintenance, including native plant cultivation and installation.
“Our goal is always to plant low growing native plant species," Ogle said. "This one in particular that we are standing in today, this is what I would call vegetation enhancement.”
This 5-megawatt grid-tied 20-acre solar array was installed four years ago by Today's Power, Inc., in partnership with Ozarks Electric Cooperative on turf grass pasture owned by the city of Fayetteville, which owns a minority power share, as part of its strategic municipal clean energy plan.
“Once we saw the broomsedge coming up, we knew we couldn't really get rid of it," Ogle said. "It would have been like trying to get rid of Bermuda grass, so we just decided to embrace it.”
The native broomsedge has completely overtaken the non-native grass, sprouting from the field’s underground native seed bank. Ogle said that compared to turf grass, native grasses on solar fields can boost power generation.
“There is some research that does show that native grasses keep the actual modules cooler," he said, "because the ground temperature stayed lower compared to if it was mowed, which is one of the worst things you can do.”
Gasoline-powered mowing produces polluting carbon emissions and can cause mechanical collisions with solar panels, ground mounts and electrical equipment.
Botanist Jennifer Ogle has a research interest in solar natives. She’s Collections Manager at the University of Arkansas Herbarium, which documents the diversity and distribution of Arkansas plants. She said native grasslands provide certain benefits to large-scale solar system ecosystems.
"Bermuda grass roots occupy the top six inches of the soil profile," she said. "By contrast, native grasses and wildflowers will occupy much more of the soil profile. So the the grasses you see here, some of them can grow four feet deep, resulting in better soil stabilization, less soil erosion, and better water quality. Around the solar arrays the water is absorbed into the roots of the plants, and slowed down as it moves into the the ditches and then into waterways. The White River is just a stones throw from here, which is Beaver Lake, our drinking water source."
Jennifer Ogle said that managed native plants on solar arrays also benefit pollinators.
“As opposed to a monoculture of turf grass such as Bermuda grass, which doesn't really attract pollinators at all, when you plant a diversity of native wildflowers and grasses, you do attract important pollinators," she said. "And as many of us know, important pollinators are on the decline, some have disappeared. And if you have agricultural fields nearby, then it benefits humans because we see increased yields, because those insects are pollinating crops as well. Insects also attact birds, especially when they're raising young. Reptiles, amphibians, small mammals and even large mammals eat insects, and they might use the native plants, eating the stems or seeds. And so we get a diverse assemblage of insects that in turn encourages other animals to use the place.”
Jennifer Ogle is collaborating with J.D. Willson, a herpetology professor in the Department of Biological Sciences at the University of Arkansas and director of Willson Lab, on a research grant project examining large-scale solar array habitats.
“We've recently, in the last six months or so, started a big study funded by the U.S. Department of Energy through their solar energy technologies office, which looks at the benefits of planting native vegetation and other aspects of encouraging wildlife use in solar facilities," Willson said.
Project collaborators also include experts with the U.S. Geological Survey, Arkansas Game and Fish Commission, U.S. Fish and Wildlife Service, as well as Isaac Ogle with Comprehensive Botanical Services. Willson lauds exponential solar development across the U.S. over the past five years to reduce carbon emissions but said that building biodiversity into that clean energy matrix is mission-critical.
“Just in Arkansas we’re seeing dozens of large-scale facilities going in every year," Willson said. "There's a real need because they're going in faster than the science that exists on how to best manage them for everybody's benefit, and so we're trying to catch up and figure out what we can do with the solar sites to increase biodiversity value. We feel that there's a tremendous potential for encouraging wildlife use especially grassland species. We have these huge set aside areas often behind a fence with grassy vegetation, so why not manage that in a way that's going to increase biodiversity, its value for wildlife conservation.”
Willson’s $1.3 million research project, “Wildlife in Solar Through Native Planting,” will compare wildlife occupancy and species richness in native solar arrays with conventionally managed solar turf grass and gravel sites. The team is deploying wildlife surveys, including visual and acoustic sampling, to measure the presence of birds, bats, terrestrial mammals, reptiles, amphibians, and pollinators across 90 sites in Arkansas, Kansas, and Oklahoma.
“Basically the plan is to sample a large number of sites but do as much remote sampling as possible," Willson said. "So we're using methods that allow us to go out and say put out a recorder or a device that captures images of wildlife and allow data collection for long periods of time while we're not there because these sites are spread out and logistics of access to these sites offer challenging so we've got to make interesting methods that allow us to do that.”
Willson is also researching how wildlife reacts to vastly reduced human traffic on gated, fenced solar ecosystems. To illustrate, he shows a mature yellow-spotted black salamander, a Willson lab resident.
“This is a good example of a species that we hope might use these native managed solar arrays and an indication of how the surrounding landscape also influences what's present in these sites," he said.
Willson said while existing research on solar facilities is directed at specific species, the scope of this federal research project is biodiverse. Standing nearby, Ben Stratton, a PhD student at Willson Lab, said he's basing his dissertation on the presence of reptiles and amphibians in native solar arrays, using remote surveillance along drift fences to temporarily catch creatures.
"And so instead of having to come out to the fence every day, we mount one of these fancy cameras that senses motion and temperature, taking photos automatically of anything moving in front of it," Stratton said. "So we can set these drift fences up within the arrays and get a pretty good idea of what reptiles and amphibians are moving through, which would be really hard to detect just by walking around and looking for them.”
The research team will also monitor for mammals, including coyotes, bobcats, rabbits, woodchucks, and skunks, in native solar ecosystems. According to the Solar Energy Industries Association, a record 32 gigawatts (GW) of new solar capacity has been developed this year, a 52% increase from 2022 – enough solar energy to power over 12 million homes.
“Now as solar becomes more popular, the arrays are becoming very, very, very large," Isaac Ogle said, "way, way larger than this site. I've worked on sites that are 2,000 acres, some of which are using agrovoltaics, incorporating sheep grazing, for example to keep the grasses down, rather than reestablishing natives, or planting native seed, which isn't cheap. Nor is the process of removing non-vegetation to plant native vegetation."
He said certain large-scale solar power producers are also cultivating permanent pollinator plots to serve as way stations for vulnerable species like monarch butterflies. Key goals of the four-year research project are to determine best site management and landscape attributes to increase biodiversity within solar arrays. The project will also engage stakeholder groups across the south-central U.S. to help enhance local solar array wildlife habitats.
