Land Use Change Impacts on Air Quality and Climate

The authors review current understanding of the interplay between land use change and atmospheric chemistry, with a focus on short-lived atmospheric pollutants. Both natural and anthropogenic land use change may substantially impact global air quality, with significant radiative effects on global and local climate. In particular, they focus on how historical and projected land use change will alter emissions of BVOC, soil NOx, dust, smoke, and bioaerosol, as well as the dry deposition of ozone. These constitute the key drivers of air quality changes related to a dynamic land surface. The review suggests that land use change has led to an overall cooling over the 20th century, with aerosol effects alone equivalent to 10-50% of the aerosol direct radiative forcing due to anthropogenic emissions. This cooling is likely to continue through the 21st century, but is subject to large uncertainties associated with future agricultural practices. In an era of declining pollution emissions, anthropogenic land use change may become the dominant human fingerprint on ozone and aerosol climate forcing. In addition, natural land use change represents a critical climate feedback which impacts both air quality and our assessment of how anthropogenic pollution has affected cloud formation, and the associated climate cooling.