The ecological impacts of agrivoltaics in semi-arid grasslands

Abstract

The rapid expansion of solar energy infrastructure onto agricultural lands presents a critical challenge: how to meet renewable energy goals without compromising ecosystem integrity. While agrivoltaic systems theoretically enable multifunctional landscapes providing both energy and ecosystem services, comprehensive understanding of their ecological impacts remains limited. I conducted multi-scale assessments of ecosystem responses to single-axis tracking solar arrays in Colorado's semi-arid grasslands. Through controlled experiments at Jack's Solar Garden and landscape surveys across nine installations, I examined how solar infrastructure affects carbon cycling, plant communities, arthropod populations, and forage productivity and quality. In this dissertation I discuss how solar energy infrastructure and agrivoltaic management affect a variety of ecosystem functions and how these findings can inform land management, regulatory policies, solar array design, and future research. My research revealed that solar arrays create distinct microclimates that spatially reorganize ecosystem functions at small scales. Beneath panels, reduced light availability and precipitation interception decreased soil water content relative to open areas, resulting in 27-30% lower aboveground productivity and 31% reduced soil CO2 flux. However, carbon stocks in surface soils (0-15 cm) increased by 25% under panels three years post-installation, suggesting enhanced carbon stabilization despite lower productivity. Edge microclimates, receiving redistributed precipitation from panel runoff, showed higher soil moisture than open areas and maintained comparable productivity while supporting intermediate carbon cycling rates. Notably, belowground net primary productivity in open areas between panels exceeded under microclimates by 59%, with roots shifting allocation patterns under panels to favor deeper soil layers (50% at 15-30 cm versus 30% in open areas). Vegetation management strategies interacted strongly with solar microclimates to influence ecosystem service provision. While native seed mixes were intended to enhance pollinator habitat and biodiversity, establishment challenges led to dominance by non-native rhizomatous grasses (86% cover) across native treatments. Pasture vegetation produced 65-100% higher aboveground biomass than native treatments. Floral resources were concentrated in open areas between panels, which supported 2.7-fold more flowers than under-panel positions, though irrigation tripled flower production beneath panels. Forage quality showed complex spatial patterns: despite 30% lower forage production under panels, the quality of forage was higher due to greater concentrations of crude protein. Landscape-scale surveys across nine commercial solar installations 5-8 years post-construction revealed a surprising disconnect between plant and arthropod communities. Despite 19-47% higher plant species richness, 21-37% greater Shannon diversity, and 1-15% higher total vegetative cover in solar arrays compared to adjacent control sites, arthropod communities showed consistent negative responses. Flying arthropod abundance declined by 48% overall, with Coleoptera (-65%) and pollinators (-50%) showing the strongest reductions. Ground-dwelling arthropods decreased by 27%, driven primarily by mixed feeders (-71%) and predators (-50%), while only Hymenoptera (primarily ants) showed a positive response (non-significant). This decoupling of plant diversity from arthropod abundance suggests that physical infrastructure effects and/or typical solar array management through mowing may override the benefits of enhanced plant resources. These findings demonstrate that agrivoltaic systems create novel ecosystems characterized by spatial heterogeneity in resource availability and ecological processes. While solar infrastructure imposes clear constraints on certain ecosystem components—particularly mobile arthropod communities—the reorganization of plant productivity, carbon cycling, and forage resources suggests opportunities for management optimization. The persistence of ecosystem services depends critically on recognizing and working with the inherent spatial heterogeneity created by solar arrays rather than attempting to homogenize management across microclimates. Strategic approaches that leverage high-productivity edge zones for forage production, maintain open areas for pollinator resources, and utilize under-panel areas for carbon sequestration could optimize the multifunctional potential of grassland agrivoltaic landscapes. I hope that this work will help guide responsible stewardship of our working lands for future generations, ensuring that renewable energy expansion enhances rather than diminishes the ecological foundation upon which both human and natural communities depend.