Articles | Volume 16, issue 23
Research article
05 Dec 2016
Research article |  | 05 Dec 2016

The impact of historical land use change from 1850 to 2000 on secondary particulate matter and ozone

Colette L. Heald and Jeffrey A. Geddes

Abstract. Anthropogenic land use change (LUC) since preindustrial (1850) has altered the vegetation distribution and density around the world. We use a global model (GEOS-Chem) to assess the attendant changes in surface air quality and the direct radiative forcing (DRF). We focus our analysis on secondary particulate matter and tropospheric ozone formation. The general trend of expansion of managed ecosystems (croplands and pasturelands) at the expense of natural ecosystems has led to an 11 % decline in global mean biogenic volatile organic compound emissions. Concomitant growth in agricultural activity has more than doubled ammonia emissions and increased emissions of nitrogen oxides from soils by more than 50 %. Conversion to croplands has also led to a widespread increase in ozone dry deposition velocity. Together these changes in biosphere–atmosphere exchange have led to a 14 % global mean increase in biogenic secondary organic aerosol (BSOA) surface concentrations, a doubling of surface aerosol nitrate concentrations, and local changes in surface ozone of up to 8.5 ppb. We assess a global mean LUC-DRF of +0.017, −0.071, and −0.01 W m−2 for BSOA, nitrate, and tropospheric ozone, respectively. We conclude that the DRF and the perturbations in surface air quality associated with LUC (and the associated changes in agricultural emissions) are substantial and should be considered alongside changes in anthropogenic emissions and climate feedbacks in chemistry–climate studies.

Short summary
Humans have altered the surface of the Earth since preindustrial times. These changes (largely expansion of croplands and pasturelands) have modified biosphere–atmosphere fluxes. In this study we use a global model to assess the impact of these changes on the formation of secondary particulate matter and troposphere ozone. We find that there are significant air quality and climate impacts associated with these changes.
Final-revised paper