Quantifying the effect of air pollution on soil carbon sequestration using an EU-wide thermal inversions dataset

The harmful effects of air pollution on human health and well-being are well-studied. However, research on the effects of air pollution on the non-human environment is still sparse. We add to this by investigating the causal effect of particulate matter (PM2.5) on vegetation and soil invertebrates throughout Europe. To do so, we exploit the quasi-random variation in air pollution concentration caused by thermal inversion episodes in an econometric instrumental-variable setting, with the help of a dedicated new dataset of thermal inversion episodes across Europe. With this econometric technique, we can estimate the causal effects of an increase in air pollution on soil variables taken from the LUCAS database. We focus particularly on processes related to carbon sequestration. A pollution-induced reduction in soil carbon sequestration constitutes a reduction in ecosystem services which can be monetised by estimating the additional economic damages arising from this carbon cycle feedback and the climate change impacts it causes. Results from a preliminary analysis in the UK suggest that a 1 ug increase in PM2.5 concentrations would imply a reduction in topsoil carbon sequestration of up to 2 MtC across England, which is substantial compared to annual UK CO₂ emissions of around 80 MtC. These results indicate that the effect of air pollution on soil biota and soil carbon sequestration might be a major overlooked damage which is to a large extent caused by the combustion of fossil fuels. Consequently, accounting for this effect allows us to economically quantify the co-benefit of increased soil health and carbon sequestration that arises from reducing fossil fuel emissions through climate change mitigation policies.