2025 Theses Doctoral

Conserving Power: Considering Animal Movement Around Large-Scale, Ground-Mounted Photovoltaic Solar Energy Facilities in the United States

Levin, Michael Oliver

Photovoltaic (PV) solar technology is the fastest growing energy generation method around the world, projected to eclipse wind and hydropower by 2029 to become the largest global source of renewable energy. In the United States, most solar energy generation comes from large, ground-mounted PV solar facilities (GPVs) that produce energy at the utility scale. By August 2024 there were at least 4,185 GPVs in the US with a combined capacity of 70,060 MWAC, enough to contribute more than 4% of the energy generated in the US and cover an area larger than 1,600 km².

This rapid development of PV solar is a critical step towards the decarbonization of the US energy sector, but its burgeoning physical footprint does not come without certain tradeoffs—the conversion of a parcel of land to a GPV can generate conflict with other place-based considerations, particularly biodiversity conservation. The GPV construction process converts a parcel of land to a relatively industrial land-use and land-cover, and these substantial alterations to the landscape can generate both positive and negative effects on wildlife. There is a small but growing body of research describing the relationship between GPV infrastructure and wild plants and animals, most of which is focused on the impacts of habitat loss and alteration generated by the installation of a GPV. One critical gap in our growing understanding of that relationship is how the unique facets of GPV infrastructure interact with the way species move through a landscape. This dissertation contains four chapters designed to address that knowledge gap and more broadly contextualize the relationship between GPV development and biodiversity conservation.

In Chapter 1, I systematically reviewed more than 150 peer-reviewed solar suitability assessments—spatially-explicit assessments of a landscape to determine the locations most suitable for GPV development—to determine how criteria relevant to biodiversity are used in such analyses globally. I found that biodiversity-relevant criteria seemed to be used in solar suitability analyses primarily to meet legal requirements, and, thus, may not adequately account for the potential effects of solar infrastructure on local and/or regional biodiversity. To provide applied context to these results, I subsequently co-hosted an expert panel with collaborators at UC Davis. The panel identified two primary barriers to incorporating biodiversity-relevant criteria into solar suitability analyses: a lack of quality data at relevant scales, and weak regulatory requirements that govern how biodiversity concerns are incorporated into solar siting.

For Chapter 2 I compared three datasets describing the spatial extent, or footprint, of US GPVs. Two datasets are publicly available and delineate the area of PV panel arrays. The third is maintained behind a paywall by a private company and delineates the broader area within a GPV’s fence line. This comparison showed that these datasets have specific analytical contexts to which they are best suited due to differences in their definition of “footprint” and the methods each used to delineate GPV footprints. This included calculations of the cumulative US GPV footprint, where area estimates derived from the datasets describing only PV panel arrays were as much as 34% smaller than that of the dataset describing the area within GPV fence lines, which had substantial implications for calculations of land-cover change.

Chapter 3 built on the core components of its preceding chapters by assessing the overlap between spatially explicit projections of US GPV development and land that may be important for animal movement—those regions likely to support movement between large protected areas or climate-change-induced migration. I found that there could be a substantial overlap between solar energy development and land important for animal movement: across projections, 7–17% of total development is expected to occur on land with high value for movement between large protected areas, while 27–33% of total development is expected to occur on land likely to support climate-change-induced migration.

Finally, in Chapter 4, I anchored the concepts explored in the previous chapters with a case study of bobcat movement around a GPV in eastern North Carolina. After trapping and tracking this bobcat for several months in 2024, we use the data she provided to construct a digital twin of a bobcat in a North Carolina solar landscape. Digital twins are the virtual replication of a physical entity; we modeled the movement of this bobcat using integrated Step Selection Functions and, using the coefficients for model covariates, virtually replicated the movement of bobcats through present and potential North Carolina solar landscapes. I found that 1) decreasing the barrier effect of GPV fencing could increase bobcat usage of the area within a GPV, depending on the quality of potential habitat inside the facility; 2) the presence of a corridor within a GPV likely facilitates bobcat movement through it; 3) GPV development in land cover categories that facilitate animal movement may lead to more substantial changes in habitat use than development in categories less conducive to animal movement; and 4) the spatial arrangement of GPVs in an area can produce different patterns of habitat use for an animal in that landscape.

These chapters shed light on the present relationship between GPV development and biodiversity, potential future interactions between a burgeoning GPV footprint and animal movement, and methods that can be used not only to predict interactions between wildlife and GPV infrastructure but design and site GPVs to mitigate their negative impacts. Solar energy is an essential part of a carbon-neutral future, and biodiversity considerations are a critical component of solar energy development—this body of research helps align their respective goals.