Agricultural land use and land cover change can alter the surface energy budget and influence temperatures. Given that agroecosystem productivity is sensitive to extreme temperatures, exploring how historical changes in agricultural land use have influenced temperatures is useful for understanding future exposure to extreme conditions. Here we examine interactions between land use and temperature extremes at local, regional, and global scales using remote sensing, weather station, and agricultural inventory data. At the local scale, we use a dataset of US agricultural land cover change from 2008-2012 based on high-resolution remote sensing data. We examine shifts in the surface energy balance following land conversion to cropland using MODIS-derived land surface temperature, albedo, EVI, and estimated evapotranspiration. At the regional scale, we associate USDA agricultural inventory data on irrigation, crop area, and crop productivity since 1910 with 95th percentile summer temperature trends from GHCN weather stations. At the global scale, historical datasets of crop productivity and irrigation since 1961 are examined as they relate to 95th percentile temperature trends in seven major temperate crop production regions.
Results/Conclusions
Analyses across all three scales indicate a substantial influence of agricultural land use on extreme temperatures during summer. Recent land cover change in the Southern Great Plains, for example, shows that conversion of grass to maize resulted in roughly a doubling of peak EVI and estimated ET. Peak land surface temperature (over a 16-day period) declined by ~5°C. More generally, there is strong spatial correlation between increased summer crop productivity and decreased summer temperature extremes at weather stations across the continental US. This relationship holds for both irrigated and rainfed lands, but with the important caveat that rainfed lands do not sustain cooling during drought conditions. Similar results are found at the global scale for other major summer cropping systems, including in the Canadian Prairies, Argentina, and East Asia.