Revisiting the land use conflicts between forests and solar farms through energy efficiency

Forests and solar energy are both critical to achieving the climate goals proposed by the Paris Agreement. However, large-scale deployment of solar farms requires vast land areas, potentially posing conflicts with other land uses. For example, solar farms have been built in forested regions or with a direct cost to forests (through deforestation). Here, we evaluated land-use conflicts between forests and established solar farms worldwide, and further assessed the energy efficiency effect of placing solar farms over forests using simulation results from seven state-of-the-art Earth system models. Our results, based on remote sensing analysis, showed that 6320 solar farms (9.14%) exhibit land-use conflicts with forests, accounting for 4.9% of the total solar farm area. The capacity factor (CF) of solar farms was found to decrease with increasing forest coverage because of enhanced cloud formation and reduced solar radiation. Even though deforestation was shown to be able to increase the local CF, in deforestation areas CF was still found to be lower than over open land (cropland or grassland). Moreover, the effect of a significantly increased CF following deforestation was found to take about 36 years to emerge, potentially exceeding the service lifetime of a solar farm (25-30 years). Our results highlight the fact that building solar farms over forests or through deforestation leads to no gain in energy efficiency compared to open land, and hence should only be carried out with great caution or completely discouraged.