Influencing mechanism of climate and human activities on ecosystem health in the middle reaches of the Yellow River of China

Global and regional environmental changes caused by climate and human activities have profoundly affected terrestrial ecosystem health. Nevertheless, few studies have been deeply dissected the influencing mechanism of climate and human activities on ecosystem health. In this study, the Middle Reaches of the Yellow River (MRYR) was choosed as the study area, and the improved VORS model was adopted to dynamically assess the ecosystem health level in the MRYR. Then, the influence mechanism of climate and human activities on ecosystem health was deeply analyzed. Our results showed: (1) The ecosystem health level in the rapidly urbanized areas, the ecologically fragile areas in the midwest regions and the mountainous - plain transition zone has a dynamic local spatial structure and spatiotemporal interaction process. (2) Topography, land urbanization, economic urbanization, population urbanization, agricultural activities, environmental pollution, and regional policy have a significant effect on the ecosystem health. (3) In the mid-eastern urban agglomerations, the impervious surface increase and the decrease of ecological land use lead to the increased negative effects of potential evapotranspiration on the ecosystem health of urban agglomerations. Topography has a long-term inhibitory effect on urban expansion, which weakens the negative impact of urbanization on mountain ecosystem health. The negative impact of economic urbanization on the mid-eastern shows a "core-edge" structure with Xi'an metropolitan area, Luohe River Basin, Fenhe River Basin, Taiyuan metropolitan area and Zhengzhou metropolitan area as the core. (4) In terms of the interaction between influencing factors, the interaction between climate and human activities on ecosystem health shows significant differences between the east, middle and west.