The impacts of ground-mounted solar parks on soil health in the UK

Soils are a key natural capital asset. Soil health, defined as the capacity of a soil to function as a living system, is a vital component of wider ecosystem processes and functioning, including the flow of multiple ecosystem services. Land use change is an important factor influencing declines in soil health globally. To meet demand for low carbon energy, ground-mounted solar parks (SPs) have expanded rapidly in recent decades, incurring significant land use change, with predictions that UK solar capacity could quadruple by 2050. There is potential for both positive and negative impacts of SPs on soil health - SPs present a relatively unique land use change, in that large areas of land remain physically undisturbed but are shaded by panels. This shading can alter microclimate metrics under panels, including air and soil temperature, soil moisture, photosynthetically active radiation and humidity, which may impact indicators of soil health. Further, the majority of SPs in the UK are developed on former agricultural land, often intensively managed. Arable land use is one of the most detrimental to overall soil health, whilst there is significant evidence supporting the benefits of taking agricultural land out of cultivation, including increased soil carbon, reduced erosion, compaction, and pollution. Considering the land use requirements and microclimatic variation within SPs, it is critical that their impacts on soil health are understood, yet research on solar park-soil impacts remains sparse.

We investigated the impact of location within SPs (under solar panels and in gap areas) and the influence of prior land use (arable and grassland) on physical, chemical, and biological indicators of soil health, to address this knowledge gap and provide one of the first quantifications on the impacts of SP development on soil health.  Preliminary results suggest no difference in indicators with SP prior land use, however bulk density and inorganic phosphorus were significantly lower in gap areas compared to under panels, whilst organic matter and microbial biomass carbon were higher in gap areas. These results suggest that soil health may be degraded under the shade of solar panels.

However, on-site management decisions such as livestock grazing, wildflower planting and mowing regimes likely influence soil health indicator values and vary across SPs. Further, the SPs studied have been operational since 2014, a relatively short time in terms of soil health. As such, further research is required across spatial and temporal scales, considering the impact of SP management actions to accurately infer SP impacts on soil health.