Global crop yield reductions due to surface ozone exposure: 1. Year 2000 crop production losses and economic damage

Exposure to elevated concentrations of surface ozone (O-3) causes substantial reductions in the agricultural yields of many crops. As emissions of O-3 precursors rise in many parts of the world over the next few decades, yield reductions from O-3 exposure appear likely to increase the challenges of feeding a global population projected to grow from 6 to 9 billion between 2000 and 2050. This study estimates year 2000 global yield reductions of three key staple crops (soybean, maize, and wheat) due to surface ozone exposure using hourly O-3 concentrations simulated by the Model for Ozone and Related Chemical Tracers version 2.4 (MOZART-2). We calculate crop losses according to two metrics of ozone exposure - seasonal daytime (08:00-19:59) mean O-3 (M12) and accumulated O-3 above a threshold of 40 ppbv (AOT40) - and predict crop yield losses using crop-specific O-3 concentration:response functions established by field studies. Our results indicate that year 2000 O-3-induced global yield reductions ranged, depending on the metric used, from 8.5-14% for soybean, 3.9-15% for wheat, and 2.2-5.5% for maize. Global crop production losses totaled 79-121 million metric tons, worth $11-18 billion annually (USD2000). Our calculated yield reductions agree well with previous estimates, providing further evidence that yields of major crops across the globe are already being substantially reduced by exposure to surface ozone - a risk that will grow unless O-3-precursor emissions are curbed in the future or crop cultivars are developed and utilized that are resistant to O-3. (C) 2010 Elsevier Ltd. All rights reserved.