Impacts of climate factors and human activities on NDVI change in China

Vegetation plays a crucial role in terrestrial ecosystems, and there has been a substantial shift in global vegetation cover in recent decades. China is recognized for its substantial impact on global vegetation cover changes, which are influenced by both climate change and human activities. Therefore, this research aims to assess the respective influences of climate modification and human activities on vegetation variations in China. First, the changes in vegetation cover are explored between 1982 and 2020 using satellite-image derived vegetation index, known as the Normalized Difference Vegetation Index (NDVI). Second, a multiple regression model based on time-lag analysis is used to simulate NDVI. In addition to common climatic factors such as temperature, precipitation, solar radiation intensity and relative humidity, the atmospheric CO2 concentration to directly reflect climate change is considered in this model. Finally, the relative influence of climate variation and human activities on the alteration of vegetation cover is determined based on reconstructed NDVI. Results: (1) Precipitation and solar radiation are the most important influences, while carbon dioxide concentration and relative humidity have the least influence. (2) The simulation error before 2000 was 0.875%, which was considerably lower than the error after 2000. (3) After 2000, human activities favorably affected vegetation recovery in most of the study area, with an average degree of influence of >30%.