Detected global agricultural greening from satellite data

The global vegetation greening trend in the past three decades has been detected from satellite observations, but few studies focused on agricultural greening. We used two long-term satellite LAI datasets and statistical methods to verify a significant greening trend in global cropland from 1982 to 2015. Agricultural greening trends [6.55 +/- 1.38 (10(-3) m(2) m(-2) yr(-1))] are more than twice that of natural vegetation [3.15 +/- 0.89 (10(-3) m(2) m(-2) yr(-1))] within the key agricultural zone in the Northern Hemisphere (10 degrees N-50 degrees N). Agricultural greening contributes near one-third (27.4% +/- 4.3%) of Northern Hemisphere greening. In less developed regions (Asia, South America, and Africa), the primary reasons for agricultural greening are cropland expansion and cropping systems reforming in a way that extends growing seasons, whereas in developed regions (North America, Australia and Europe) these are agricultural intensification (Green Revolution). Agricultural greening trends in less developed regions are greater than in developed regions. Agricultural intensification is accompanied by cropland decreases within developed regions, whereas this is accompanied by cropland expansion in less developed regions, which is different from previous conclusions that agricultural intensification was not generally accompanied by decline or stasis in cropland area. Our results suggest that global cropland is experiencing significant eco-environmental changes. The roles that agricultural greening plays in global environmental and climatic changes are worthy of further research.