Relevance evaluation and spatial differentiation analysis between green development and environmental footprint in China's three typical mega-urban agglomerations

This study constructs a comprehensive framework for exploring the relevance between green development level and environmental footprint in three typical mega -urban agglomerations of Yangtze River Economic Belt (YREB) of China. This framework consists of the three-dimensional ecological footprint (EF3D), carbon footprint (CF), cloud model, and Environmental Kuznets Curve (EKC). Results reveal that there exist an increased EF3D and a decreased ecological carrying capacity in the YREB, with annual change rates of 4.45% and -0.46%, respectively. According to ecological footprint depth, 24.61, 17.59, and 30.89 times of current local land area are required for supporting regional development in the YREB upstream, midstream, and downstream urban agglomerations, respectively. There is an increased tendency in CF, especially in the midstream urban agglomeration with an increased rate of 5.25%. Carbon pressure is mostly contributed by crude oil (34.47%) and raw coal (31.55%). Moreover, green development level in the YREB shows an increased tendency with an annual rate of 0.5%, and that in the downstream urban agglomeration is generally greater than other areas. The relevance between green development level and environmental footprint is mainly inverted U-shaped or inverted N -shaped EKC types. CF in the YREB and its upstream urban agglomeration begins to decline when green development levels are 3.44 in 2020 and 3.26 in 2020, respectively. EF3D in the midstream urban agglomeration starts to fall when green development level reaches 3.36 in 2019. EF3D from cultivated land and fossil fuel land has a positive impact on the improvement of relevance. Overall, the developed framework can be applied to areas where there is a conflict between economic development and environmental protection. Furthermore, dynamic prediction of green development level and environmental footprint as well as their correlation mechanism under different scenarios are still required for enhancing environmental sustainability and promoting regional coordinated development.