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Large-scale carbon-free energy generation projects such as utility-scale solar energy (USSE) arrays help mitigate the energy sector’s contribution to climate change and are rapidly expanding throughout the U.S. However, the expansion of USSE sites is associated with immediate and longer-term ecological impacts, many of which have yet to be assessed. Quantifying the ecological impacts of USSE arrays will help to identify synergies and trade-offs between energy generation and terrestrial conservation goals. The overall goal of this research is to characterize the ecological impacts of USSE sites located on fallowed farmlands in San Luis Obispo County, California in a seasonally explicit manner. Fallowed agricultural landscapes and rangelands represent a particularly promising area for the deployment of solar arrays because these systems typically are significantly altered from their native conditions; therefore, array placement may not have significant further deleterious ecological impacts and may also provide the potential to recover ecologically with shifts in management practices. We studied how arrays impact a suite of ecological properties, focusing on two USSE arrays in California’s Coast Range Valley: Topaz Solar Farm (developed 2014)and Goldtree Solar Farm (developed 2018). Topaz, which is situated on previously disturbed agricultural land in Carrizo Plain, was seeded with a native seed mix prior to installation and uses rotational grazing to control vegetation growth. The climate is more arid at Topaz than at Goldtree, which is located approximately 14 miles from Morro Bay. Goldtree is situated on sheep pastureland and is also managed with a rotational grazing regime, though with a higher intensity than at Topaz. Solar farms created distinct patterns of heterogeneity, which then affected plant community changes and soil nutrient cycling. Partial shading in areas adjacent to panels increased species richness with more native species and higher functional diversity, especially in drought conditions. Full shading in areas directly under plots increased plant moisture content and plant nitrogen content during drought conditions. This may be beneficial in supplying plants with greater water availability and nutrients, especially during drought years. In solar array footprints, ecosystem respiration (plant and soil CO2 flux) was reduced, suggesting that shading on solar farms can improve carbon sequestration on disturbed agricultural land if organic matter inputs outpace carbon loss in this novel ecosystem. Thus, our study demonstrated that solar farms offer the potential for improvement of ecosystem services, if placed on previously disturbed landscapes such as fallowed farmland and combined with other conservation management practices. |
