Impacts of climate changes and extremes on the yields and GHG emissions for major crops in China

Abstract:

Many agricultural regions around the world will get much wetter or much drier in a warmer climate. Assessing how climate changes and extremes will impact the yield and GHG emissions over space and time, which is critical for global food security and mitigating GHG emissions. Here we conduct the state-of-the-art estimate on the spatial-temporal variability of crop yield and GHG emissions for the major crops (wheat, maize, and rice) in China during 1983-2012, using an improved agricultural ecosystem model (DLEM-AG2.0) and the meta-analysis covering a lot of field GHG emission/warming experiments. Results showed that Relative to the 30-year average, climate changes decreased crop yields and GHGs emissions by 7.7% and 5.0% on average for wheat, maize, and rice. Wetter-warmer events (WW) decreased crop yields by 10.88%, on average, while the drier-warmer events (DW) hindered crop yields by 13.8%. However, in contrast to common perception, GHG emissions induced by WW were 11.3% more than those induced by DW. The heat exceeding annual average temperature by 2.0 ^°C, the yield losses of these crops under the wet extremes (SPEI > 1.0) were as severe as those under the drought extremes, corresponding with an increase of 21.4% in GHGs emissions. At a large fraction of pixels, on average, WW had a great stimulation on the crop yield losses as important as the drier-warmer but exacerbated more GHG emissions. Our results imply that wetter-warmer world threatened the food security and greenhouse gas mitigation as great as or even greater than the drier-warmer world than what we commonly expect. Our study highlights that a major challenge will pose to large GHG emissions mitigation efforts to achieve the goals of Paris Agreement.