Vegetation management utilizing sheep grazing within utility-scale solar: Agro-ecological insights and existing knowledge gaps in the United States

Abstract

Common themes exist in the development of photovoltaic (PV) systems, globally. Capturing sunlight for energy production requires a significant land-use footprint, thus resulting in limitations that prohibit development of solar sites. Diverse regions across the U.S. are being utilized for PV development with varying population density, climate, and forage production potential. Energy usage is expected to grow with increased demand from industrial and residential segments. Internationally, the U.S. ranks second in energy usage and is the primary contributor to the growing energy demand. As utility-scale solar installations continue to expand across the U.S., and specifically pastures and rangelands, the need for sustainable vegetation management has become a critical operational consideration. Grazing with sheep presents a viable solution, offering both economic and ecological benefits by controlling vegetation growth without compromising (PV) panel efficiency. This review synthesizes current research on the integration of sheep grazing within solar sites, often referred to as "solar grazing," with a focus on the agro-ecological interactions, operational challenges, and potential for industry growth. This review also examines the critical factors influencing vegetation management, including regional climate variability, forage production potential, and species-specific grazing behaviors. Additionally, the role of solar grazing in fire mitigation, biodiversity enhancement, and soil health improvement is explored. Despite the promise of this dual-use strategy, several knowledge gaps persist, particularly regarding the long-term ecological impacts on native plant communities, optimal sheep stocking densities, and the balance between forage production and sheep nutrition within these solar sites. Current trends in solar development are contrasted with the declining sheep population in the U.S., raising concerns about whether the American sheep industry can meet the growing demand for solar grazing. Moreover, the integration of solar grazing introduces new challenges in animal health and welfare, particularly in regions with increased parasite concentrations or limited access to water and supplemental feed. This review highlights the need for further research on adaptive management practices, as well as the development of infrastructure and industry support to ensure the sustainability of solar grazing in diverse regions of the U.S.