Evaluation of water-carbon-ecological footprints and its spatial–temporal pattern in the central plains urban agglomeration

Maintaining the stability of natural capital stock is an important basis for realizing regional sustainable development goals. Based on the improved three-dimensional (3D) footprint family model, this study analyzes the spatial and temporal evolution of the natural capital utilization of water-carbon-ecological footprints in the Central Plains Urban Agglomeration (CPUA) from 2010 to 2020. It considers water resources, carbon emissions and ecological environment comprehensively, and establishes an evaluation system to assess the regional resource and environmental pressure. The results showed that: (1) During the period of 2010–2020, each component of the per capita water-carbon-ecological footprint of the CPUA were in deficit. Footprint depths were all greater than 1 and in a state of depleting capital stock. The water footprint depth (WFdepth) showed a large fluctuation between 1.721 and 4.302, the carbon footprint depth (CFdepth) increased from 6.025 to 7.440, and the ecological footprint depth (EFdepth) fluctuated between 4.801 and 5.779. (2) There were spatial differences in the depth of each type of footprint, with the WFdepth showing a south-high and north-low distribution, the CFdepth showing a northwest-high and southeast-low distribution, and the EFdepth showing an east-high and west-low distribution. (3) Exploratory spatial data analysis (ESDA) showed that there were spatial correlations between the various types of footprint size and footprint depth in the CPUA, and that cities showed local spatial characteristics of High-High cluster and Low-Low cluster. (4) All types of resource and environmental pressure measured were at high levels (>0.8), and the resource-environment pressure index (REPI) in the northwest showed a gradual increasing trend.