The impact of Future Land-Use and Land-Cover Changes on Atmospheric Chemistry-Climate Interactions

To demonstrate potential future consequences of land-cover and land-use changes beyond those for physical climate and the carbon cycle, we present an analysis of the impacts of land-cover and land-use changes on atmospheric chemistry and climate simulated with the chemistry-climate model EMAC. Future (2050) land-use and land-cover changes are expected to result in an increase of global annual soil NO emissions by ~1.2 TgN yr-1 (9%) whereas isoprene emissions decrease by ~50 TgC yr-1 (-12%) compared to present-day. The analysis shows increases in simulated boundary layer ozone mixing ratios up to ~9 ppbv and more then a doubling in hydroxyl radical concentrations over tropical deforested areas. However, small changes in global atmosphere-biosphere fluxes of NOx and ozone point to the significance of compensating effects. Our study indicates that assessment of the impact of land-cover and land-use changes on atmospheric chemistry requires a consistent representation of emissions, deposition, canopy interactions and their dependence on physical and biogeochemical drivers to properly account for these compensating effects. It results in negligible changes in the atmospheric oxidizing capacity and, consequently, in the lifetime of methane. In contrast, the analysis indicates a pronounced increase in oxidizing capacity as a consequence of anticipated increases in anthropogenic emissions.