Aridification and its impacts on terrestrial hydrology and ecosystems over a comprehensive transition zone in China

Abstract In China, the topography, climate, ecology, hydrology and human environment vary greatly from southeast to northwest, and a typical natural and social environmental transition zone (namely comprehensive transition zone) exists near the “Hu Huanyong line” that is a famous demographic dividing line in China, known as the Hu zone. Dry-wet climate changes in the Hu zone can have a significant impact on terrestrial ecosystems and hydrological conditions, ultimately affecting human-land relations. However, there is still a lack of clear understanding of environmental changes in the context of climate change in the Hu zone. Here, a quantitative analysis of climate change and its impact on terrestrial hydrology and ecosystems from 1951 to 2020 is presented. The results showed that there exists a significant drying trend in the Hu zone and a dramatic decrease in terrestrial water storage (TWS), indicating that the environment has become worse. Conversely, from the perspective of significant greening, the environment has improved. This contradiction is mainly due to climate change dominating the depletion of TWS, while the increase in vegetation greenness is more driven by human activities including agricultural management and ecological restoration, offsetting to some extent the negative impact of water scarcity on vegetation growth.