There’s a hum under Minnesota solar panels that engineers didn’t put in the plans. It is a biological, dense, ancient hum. Beneath the photovoltaic panels that convert sunlight into electricity, 122 species of native bees have found something that has been disappearing from the fields of half the world for decades: flowers.
It’s not a coincidence. It is the result of a management decision that costs money, requires planning and that, according to the latest science, is producing results that no one expected when the first solar panel was installed in a meadow.
The bees are disappearing. A study published in Nature Ecology & Evolutionwith data from 681 agricultural fields on three continents and more than 19,500 specimens of 910 species of wild bees, reached an uncomfortable conclusion: pesticides and habitat loss are reducing bee populations in an additive, independent way, without one factor compensating for the other. That is, having more natural habitat around a field does not neutralize the damage from pesticides. And reducing pesticides is not enough if the habitat has disappeared. They are two different problems that require two different solutions.
The work, led by Anina Knauer and researchers from Agroscope among other institutions, found that pesticides not only reduce the number of bees: they also reduce their functional and phylogenetic diversity. Communities not only become smaller, they become simpler, less resilient, less able to cope with future shocks.
A desert with seasonal flowers. In Iowa, in the heart of the American Corn Belt, 72% of the territory is covered in corn and soybean monocultures. Less than 0.01% of the original prairie remains standing. This is what researchers at Iowa State University publish in BioScience described as “an extreme example of landscape simplification”. Bees literally have very little to go to. And when the soybeans stop flowering at the end of summer, there is nothing. The colonies enter what science calls the feast-famine dynamic: the festival of flowering followed by famine that kills hives before winter.
This is the background scenario. An agricultural world that urgently needs more pollinator habitat, free of pesticides or with minimal exposure. And in that desert, solar panels are doing something no one expected.
14 floors. 122 species. And an unexpected star. A team of researchers led by Bethanne Bruninga-Socolar of Western EcoSystems Technology and James McCall of the National Renewable Energy Laboratory asked a very specific question: Of all the plants that can be grown under and around solar panels, which ones actually establish? And how many bees can they hold?
The work, published in Environmental Research Communicationstested 101 plant species in eight different seed mixtures at three solar farms in the tallgrass prairie region of Minnesota. After three years of monitoring, 14 species of flowering herbaceous plants had successfully established themselves. With those 14 species as a starting point, the researchers cross-referenced the data with an exhaustive catalog of plant-bee interactions from the same region. The result is that those 14 plants can support 122 unique species of native bees, 24% of all bee diversity in the state of Minnesota, which has 508 documented species.
The star of the system is Zizia aureathe golden Alexander, a yellow flowering plant that blooms early in the season. Alone, it supports 67 species of bees. And 36 of those species—30% of the total study—only visited Zizia aurea among all the plants studied. If it is not in the seed mix of the solar park, those 36 species have nothing.
Not all flowers are worth the same. The study also documents an important nuance: bumblebees, the group of pollinators with the most species in decline—three of the eleven species of Bombus of the study are classified as vulnerable by the IUCN: B. pensylvanicus, B. terrestrial and B. fervidus—they don’t get along with Zizia aurea. Only one species of bumblebee visited that plant. Bumblebees prefer Monarda fistulosathe wild bergamot, visited by nine of the eleven species of Bombus of the study. The practical lesson: there is no universal mix. The design of what is planted must respond to what is to be conserved.
And what if there are pesticides in the surrounding fields? He study by Toth and colleagues in BioSciencewith more than a decade of data on strips of native prairie embedded in corn and soybean fields in Iowa, systematically reviewed chemical contamination in that type of habitat. Pesticides arrive—neonicotinoids, pyrethroids, fungicides—but in concentrations that, for the best studied species, are below the damage thresholds.
And most importantly: the concentrations are no higher than in the rest of the surrounding agricultural landscape. They are not an ecological trap; They are an island of resources in a sea of fields that already have pesticides on them anyway. In addition, a diet rich in quality pollen—exactly what these plants provide—makes bees better tolerate chemical exposure. Nutrition acts as a shield. The authors of that work themselves explicitly point out that their conclusions are applicable to “other types of landscape improvements for pollinators such as hedgerows, pollinator gardens, solar installations with pollinator habitat.” It is not a journalistic extrapolation. It’s in the text of the paper.
If there are flowers inside there are bumblebees. If field studies answer the “does it work now?” published in Global Change Biology by Hollie Blaydes and colleagues at Lancaster University answers “will it still work in 2050?” The team modeled the 1,042 operational solar farms in Britain under three socio-economic scenarios for mid-century: a sustainability scenario, an intermediate scenario and a fossil development scenario with maximum agricultural intensification. The main finding is compelling: the management of the solar park is the main determining factor of bumblebee density within the park, above land use changes in the surrounding landscape.
Solar parks last between 25 and 40 years. That means decades of stable habitat in landscapes that are going to change and possibly get worse for pollinators. And there is an economic angle that is not minor either. Colonies located near diverse native vegetation avoid feast-famine dynamic which in monocultures weakens hives at the end of the season. Less artificial supplementation, less costs, better colonies for wintering, greater honey production. He study by Toth and colleagues documents that Corn Belt beekeepers tend to overestimate the risks of pesticides and underestimate the value of nutrition, causing them to fail to see the potential of these spaces for their own business. Solar companies do not have beekeepers as interlocutors. Beekeepers are not looking at solar farms as hive siting opportunities. Science has shown that synergy is possible. The logistics of making it a reality is the next frontier.
The paradox that no one planned. The infrastructure we are building to save the planet from climate change turns out to be, if managed with a minimum of ecological intention, also a refuge for the living beings that make a substantial part of our food chain possible. Solar panels that generate clean electricity and under which blooms Zizia aurea and Monarda fistulosa They are, at the same time, a response to two different crises: the climate crisis and the biodiversity crisis.
It is not automatic. It requires someone to make the decision not to plant grass under the panels. It requires someone to choose the right seeds. Requires maintenance, monitoring, design. But the scientific basis for doing so is there, and it is stronger than most solar farm operators—and most citizens—know. The humming noise under the panels was not in the original plans. But it’s already there. The question is whether we are going to listen to it.
Image | SolarPower
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