Climate change overshadows human activities in enhancing vegetation activity in Inner Mongolia

Greening is recognized to occur in China; however, it is still unclear about the change of vegetation and its attributions from climate change and human activities in Inner Mongolia, located in a typical transition climate zone from humid to arid. This study has comprehensively deliberated the variations of the Normalized Difference Vegetation Index ( NDVI ) in 2001–2018 and quantified its controls resulting from climate change and human activities. The results showed that NDVI in Inner Mongolia experienced a significant increase with a rate of 0.0018/year ( P < 0.05) during 2001–2018. Climate change dominated the NDVI variations area accounting for 55.43%, while human activities 44.57%. The effects of climate change increased from south to north. The increase in precipitation dominated the augment of NDVI in the east and middle of Inner Mongolia. Climate change had slight effects on vegetation in the drier regions due to the counterbalance effect of precipitation and vapor pressure deficit. Moreover, human activities are the chief reasons for the NDVI increase in western Inner Mongolia, especially in the arid zone. In general, ecological projects, cropland expansion, urbanization, and human management measures made positive contributions to vegetation growth. Ecological projects among all human activities were the most effective way to affect vegetation growth.