Home – Energy – A Minnesota solar project planted native vegetation under its panels and triggered a biodiversity explosion, with monarch butterflies showing up first and native bee numbers rising nearly 20-fold as the soil and plant community rebounded
At first glance, a solar farm in Minnesota looked like any other clean energy project, with neat rows of panels built to send electricity onto the grid. Then workers planted native prairie flowers and grasses underneath, and the land began to do something more surprising than generate power. It started acting like habitat.
New research on Minnesota solar sites shows that carefully planted ground cover can help restore prairie plants, improve soil conditions, and attract pollinators such as bees, butterflies, moths, flies, and wasps. The big takeaway is simple, but important. A solar farm does not have to be bare gravel, short turf, or wasted space beneath the panels.
The research focused on three large working solar farms in Minnesota, including the Chisago Solar Site, part of the Aurora Solar Project. Scientists from the National Laboratory of the Rockies (NLR), Argonne National Laboratory, the University of Minnesota, Temple University, and other partners studied how solar panels, soil, native vegetation, and pollinators interacted over several years.
Their findings point to an emerging practice known as ecovoltaics. In practical terms, that means using the land under and around solar panels for ecological benefits, not just energy production. The researchers found that native prairie can be established under solar panels, creating habitat for wildlife and pollinators while supporting soil benefits.
The most interesting part may be the wait. NLR’s InSPIRE team spent six years studying the combined effects of solar development on native vegetation, pollinators, soil, and photovoltaic (PV) performance, making it the longest and most comprehensive assessment of these interactions so far.
The prairie did not bounce back overnight. Researchers found that native habitat under solar panels can help protect soil from future erosion, but soil damaged by years of intensive corn and soybean production may take a long time to recover.
They also found that prairie vegetation needed three to four years after construction to fully establish, with some plant species not appearing until years five and six.
That slow recovery produced real numbers. In one monitoring report on Minnesota solar installations, researchers observed 72 plant species in bloom across the sites, including 45 native species. Some of the most common plants included common yarrow, daisy fleabane, prairie coneflower, blackeyed-Susan, hoary vervain, golden alexander, and several milkweed species.
Another 2024 study tested eight native pollinator seed mixes at three utility-scale solar sites in Minnesota. Native coverage under and between PV arrays rose from 10% after one year of planting to 58% after three years, while the full-sun control areas rose from 9.6% to 70%. Not perfect, but still a strong sign that solar land can grow more than electrons.
So why did monarch butterflies show up? The answer is not magic. It is milkweed.
Monarchs depend on milkweed plants to lay eggs and feed their caterpillars, and researchers specifically measured milkweed and monarch reproduction during site visits. In the Minnesota monitoring report, monarch butterfly reproduction was detected on all four sites studied, with 38 eggs and larvae observed across the season.
A higher number of eggs and larvae were found in partial-shade transects than in full-sun areas.
The butterfly story is eye-catching, but bees may be the bigger signal. A five-year field study from 2018 through 2022 found increases over time in flowering plant richness, insect group diversity, native bee abundance, and total insect abundance at solar pollinator habitat in Minnesota. The study also found positive effects on bee visits to nearby soybean flowers.
Argonne National Laboratory reported that total insect abundance tripled, while native bee numbers increased by 20 times. That does not mean every solar site will automatically become a buzzing prairie. It does show what can happen when energy developers treat the ground under panels as living space instead of leftover space.
There is also a farm angle here. In the five-year study, bee visitation to soybean flowers near solar pollinator habitat was comparable to visitation near land enrolled in the Conservation Reserve Program, and higher than bee visitation inside soybean fields or along roadsides.
That matters because rural solar projects often face local concern over land use. At the end of the day, a project that produces electricity while supporting pollinators and nearby crops may be easier for communities to understand than a fenced-off field of panels and mowed grass.
The researchers are careful not to overstate the case. Site conditions matter, and the benefits of native planting can vary by climate, soil, seed mix, and maintenance. “One of the most important results from this research is that we need to study more sites,” NLR agrivoltaics researcher Chong Seok Choi said.
The monitoring report also noted limits. Its sample size was small, one site had sheep grazing that affected flowering vegetation, and some non-native or invasive plants appeared.
That is where good management comes in, because a pollinator-friendly solar site still needs upkeep, just like a garden in a backyard needs more than one good weekend of planting.
For the most part, these studies point toward a more useful way to think about solar development. The panels produce power, but the land below them can also cool the soil, hold plants, host insects, and rebuild pieces of prairie that farming and development have pushed aside.
The lesson is not that every solar farm will become a monarch haven. It is that design choices matter. Plant the right native flowers and grasses, give the soil time, manage weeds, and the empty space beneath panels can turn into something much more alive.
The official research is available on the website of the Office of Scientific and Technical Information (OSTI).
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