Scale response and spatiotemporal correlations between landscape ecological risk and human activity intensity in the Yangtze River Delta region

Abstract: Human activity has been one of the most important factors inducing regional ecological risks in recent years. But, there are different visualization and response degree of ecological risks and human activities in different land scales. It is a high demand to scientifically analyze the correlation characteristics of regional Landscape Ecological Risk (LER) and Human Activity Intensity (HAI), in order to coordinate the territorial system of human-environment interaction for better regional high-quality development. The ever-increasing conflict can be found between ecological protection and economic and social development, due mainly to rapid urbanization. The Yangtze River Delta (YRD) is one of the typical regions with intensive human activities, remarkable economic development, and outstanding ecological status. Taking the YRD as the subject, a three-level scale of city, county, and grid was established to construct the LER and HAI assessment models, in order to characterize the spatial and temporal response at different scales. The data was also collected from the land use, nighttime lighting, and population spatial distribution in the four periods from 1990 to 2020. The Copula function, bivariate spatial autocorrelation, and coupled coordination degree models were used to reveal the spatial and temporal correlation between the LER and HAI. The results show that (1) the spatial distribution pattern of LER was high in the north of the study area, and low in the south under different scales. The high risk areas continued to decrease during 1990-2020, whereas, the low risk areas showed an increasing trend. There was the most outstanding reduction in the high risk areas at the city scale, with a decrease of 19.51 percentage points over 30 years. By contrast, there was the most significant increase in the low-medium risk and low risk areas at the county scale, indicating an increase of 16.29 percentage points over 30 years. (2) The spatial distribution pattern of HAI was high in the northeast of the study area during 1990-2020, while low in the southwest under different scales. All the regions with high HAI showed a significant increasing trend. There was a significant decreasing trend in the regions with low HAI. The high intensity region presented the largest increase at 13.42 percentage points on the grid scale, whereas, the low intensity region was the most significant decrease at 9.76 percentage points on the city scale. (3) The correlation between HAI and LER shared a positive correlation between 1990 and 2020, but the correlation between them was weakening, indicating the weak influence of regional HAI on LER. By contrast, the coupling and coordination between them showed an increasing trend from 0.3031 in 1990 to 0.3112 in 2020. It infers that the relationship between them was gradually shifting from conflict to coordination. Spatially, there was a continuous decreasing trend in the H-H clustering area. Furthermore, the L-L clustering area showed an increasing and then decreasing trend with an overall decrease. Both L-H and H-L increased significantly after 2010. The spatial correlation characteristics of regional LER and HAI were combined to manage and control the regional ecological environment. The finding can provide a theoretical basis for land management and landscape planning, together with the spatial guidelines for the regional ecological risk prevention and ecological restoration.