Solar grazing with two sheep per hectare boosts bee populations in New York

A research team from Cornell University studied how solar grazing affects insect populations at a renewable energy site in Dryden, New York.

Led by Leana Zoller, the team observed that keeping a specific number of sheep and goats near solar panels can significantly change the local environment for pollinators. The researchers conducted the experiment between 2020 and 2022 at the Cascadilla community solar plant.

They divided groups of solar panels into pens and assigned between 0 and 10 sheep per hectare to each area. While some plots were only mowed, the sheep grazed the vegetation. The team found that having an average of two sheep per hectare increased the number of bees and ladybugs by 38 percent compared to the mowed plots. Specifically, honeybee populations rose by 83 percent because the grazing conditions allowed more flowers to grow, providing food and habitats.

The study also revealed that overgrazing harms biodiversity. When the density of sheep reached six or more per hectare, bee numbers dropped by 42 to 68 percent because the flowers were depleted. The researchers noted that while eight sheep per hectare were previously thought optimal for weed control, two sheep are better for promoting biodiversity. The team suggests four sheep per hectare as a middle ground to balance vegetation control with ecological health.

Currently, between 7 and 11 percent of solar plants in the United States use solar grazing as part of an agrivoltaic practice. Nikola Kochendoerfer, a coauthor of the study who manages 700 sheep across solar plants in New York and Vermont, noted that this model allows farmers to receive payments for grazing. The findings suggest that careful management of grazing can support native plant species and local fauna in energy projects.