Case study of the effects of atmospheric aerosols and regional haze on agriculture: An opportunity to enhance crop yields in China through emission controls?

The effect of atmospheric aerosols and regional haze from air pollution on the yields of rice and winter wheat grown in China is assessed. The assessm ent is based on estimates of aerosol optical depths over China, the effect of these optical depths on the solar irradiance reaching the earth's surfac e, and the response of rice and winter wheat grown in Nanjing to the change in solar irradiance. Two sets of aerosol optical depths are presented: one based on a coupled, regional climate/air quality model simulation and the other inferred from solar radiation measurements made over a 12-year period at meteorological stations in China. The model-estimated optical depths ar e significantly smaller than those derived from observations, perhaps becau se of errors in one or both sets of optical depths or because the data from the meteorological stations has been affected by local pollution. Radiativ e transfer calculations using the smaller, model-estimated aerosol optical depths indicate that the so-called "direct effect" of regional haze results in an approximate to 5-30% reduction in the solar irradiance reaching some of China's most productive agricultural regions. Crop-response model simul ations suggest an approximate to 1:1 relationship between a percentage incr ease (decrease) in total surface solar irradiance and a percentage increase (decrease) in the yields of rice and wheat. Collectively, these calculatio ns suggest that regional haze in China is currently depressing optimal yiel ds of approximate to 70% of the crops grown in China by at least 5-30%. Red ucing the severity of regional haze in China through air pollution control could potentially result in a significant increase in crop yields and help the nation meet its growing food demands in the coming decades.