Enhanced bloom and pollinator diversity from native prairie restoration at a photovoltaic solar park

Large, ground-mounted photovoltaic solar energy projects (GPVs) are increasingly sited on former agricultural lands, creating opportunities to integrate ecological restoration as a scalable, nature-based solution to mitigate insect habitat loss and promote sustainable development. However, empirical evidence for the benefits of such efforts is nascent, particularly in water-limited regions where GPV development is rapidly expanding. We conducted an in-depth study at the UC Davis Experimental Ecovoltaic Park, a 16.3 MW single-axis tracking GPV in the semi-arid Great Central Valley of California over two growing seasons following the sowing of a tailored seed mixture comprising 12 indigenous, pollinator-attractive wildflower species. Our objective was to evaluate how restoring native California prairie to replace poorly-managed, noxious-weed communities can interact with microclimate dynamics imposed by PV modules to influence floral resources and pollinator populations. Native wildflowers on restored plots exhibited 41% and 220% greater floral richness and cover, respectively, resulting in up to six times pollinator diversity than invasive broadleaves on unrestored controls where honey bees dominated visitations. Although perennials Phacelia californica and Grindelia camporum successfully established in the second year, the natural decline of annuals, particularly sunflower Helianthus bolanderi favored by many specialist bees, was associated with a 33% decrease of overall pollinator diversity. While panel-induced shading reduced flower unit densities while enlarging display areas of several native wildflowers, it did not significantly alter pollinator community composition. The findings demonstrate that ecological restoration at GPVs can potentially reconcile renewable energy production with biodiversity conservation in harsh, weed-prone environments.