Taking farmland out of production to increase harvests might seem counterintuitive. But new and ongoing research suggests that trading some farmland for deep-rooted prairie vegetation can provide habitat for wild insect pollinators and boost overall crop yields.
Increasingly popular pollinator-friendly solar projects, which cultivate low-growing meadows underneath the panels, present an opportunity to increase food production and clean energy generation at once. For a state like Minnesota, where farming is prevalent and the solar industry is expanding, this kind of compatibility between agriculture and solar energy production is a most welcome development.
Installed solar capacity in Minnesota crossed the 1-gigawatt threshold last fall, and is set to grow sixfold by 2030 to meet the state’s 10 percent solar energy goal. The management of the land below the panels — most commonly seeded with turf grass — offers an important opportunity to provide multiple environmental and agricultural benefits in addition to carbon-free energy generation.
Last fall, our team of graduate students at the Yale School of Forestry & Environmental Studies conducted a cost-benefit analysis of solar development on farmland in Minnesota, and the results were illuminating. By developing projects as pollinator-friendly — the practice of planting deep-rooted grasses and wildflowers throughout a project site — solar developers have the potential to provide habitat for threatened pollinator species, restore important prairie ecosystems, and boost the crop yields of nearby fields. That’s right: Our model suggests a net gain in food production is possible when highly pollinator-dependent crops are grown near pollinator-friendly solar projects — even when accounting for the land taken out of production by the solar project.
While unexpected, this result has sound basis in research and practice. Iowa State University research extending over 10 years has shown that prairie strips in agricultural areas increase the abundance of native pollinators while also decreasing runoff and increasing soil and nutrient retention; crop pollination scientists in New Jersey and Michigan have published peer-reviewed research showing that an increased abundance of wild pollinators boosts yields for specialty crops. Now we have the potential to add solar to the mix.
As solar development expands throughout Minnesota, so too is attention toward the land use under the panels. Solar projects require roughly 7 acres of land per megawatt of energy production, meaning that projects installed to date occupy roughly 7,100 acres of land in the state. While that’s less than 0.03 percent of Minnesota’s 26 million acres of farmland, the compatibility of solar projects and farming is important for the continued sustainable development of the two industries.
Minnesota: first to establish standard
In 2016, Minnesota was the first state in the nation to establish a flexible and science-based standard for pollinator-friendly solar development, and several states have since implemented their own standards to encourage the practice. Last fall, Xcel Energy announced that it will require use of Minnesota’s pollinator-friendly solar standard in responses to all future solar RFPs.
In addition to the public benefits, our model indicates that pollinator-friendly solar projects could generate higher private returns for solar site owners and investors. This is mostly thanks to an estimated panel efficiency gain from the cooler microclimate created by the perennial vegetation. That also means more clean energy powering Minnesota homes and industry. Additionally, once a low-growing meadow is established under the panels, the vegetation requires less mowing and maintenance, leading to operating cost savings over the life of the project. Finally, we hypothesize that the aesthetic appeal of pollinator-friendly solar can smooth the permitting process for developers and create added benefit for the surrounding community. A field of wildflowers and solar panels seems like a pretty good neighbor to us.
Finally, our team monetized and modeled several key ecosystem services generated by pollinator-friendly solar projects: the deep-rooted plantings under the panels build soil health, improve water quality, recharge groundwater, and reduce erosion, as best practice guidance demonstrates.
Implications: Habitat plus economic boost
The implications of these findings are significant. Not only could pollinator-friendly solar development provide habitat to threatened native pollinator species, the practice could also provide a needed economic boost to Minnesota farmers. And if Minnesota met the remainder of its 2030 solar installation target with pollinator-friendly projects, the monetized environmental co-benefits range from $30-515 million, depending on the composition of surrounding farmland.
Further research is needed to more precisely quantify the ecosystem and agricultural services that pollinator-friendly solar may provide, and this is a topic of ongoing study at University of Minnesota and the National Renewable Energy Laboratory. Meanwhile, pollinator-friendly solar sites are proliferating in Minnesota and around the country, offering fertile ground for research and assessment of their economic and environmental impacts. So far for Minnesota, they are a sweet deal.
Katie Siegner, Scott Wentzell and Whitney Mann are second-year Master of Environmental Management (MEM) candidates at the Yale School of Forestry & Environmental Studies. Hallie Kennan and Maria Urrutia (also MEM candidates at Yale FES) contributed to this article as well. The group completed a semester-long economic analysis of pollinator-friendly solar development in fall 2018 for an Energy Economics & Policy Analysis class. The final paper can be found here.
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