Ecological footprint in Beijing-Tianjin-Hebei urban agglomeration: Evolution characteristics, driving mechanism, and compensation standard

Unbalancing ecological supply-demand is an obstacle to sustainable development in the Beijing-Tianjin-Hebei urban agglomeration (BTHUA), which can be efficiently addressed through regional ecological compensation. However, the driving mechanism of this unbalance is unclear, and the determination of ecological compensation standard (ECS) is not unified. This study uses the ecological footprint (EF) model and integrated inversion model to complete the intelligent evaluation and prediction of ecological supply-demand performance in the BTHUA. The extended nonlinear STIRPAT model and geographic detector are integrated to identify the driving mechanism of EF and its spatial differentiation. ECS at different spatiotemporal scales are then given with consideration of ecological service value and Monte Carlo simulation. Results reveal that EF of the BTHUA exhibits a downward trend, especially under the sustainable scenario (SSP1), falling by 16.85 %. But all cities would be still in unsafety states by 2035, with an average EF value of 6.210 hm2/cap, which is over 27 times greater than its EC. The spatial distribution of EF differs significantly, and high-value areas gradually migrate to the north. The variation of EF is primarily influenced by industrial structure, with population factors and environmental factors following. Per capita GDP is a key factor causing spatial differentiation of EF. The key driving factors and their explanatory powers on EF vary across cities, and the interaction of multiple factors affects EF more than a single in the BTHUA. Past-to-future ECS of the BTHUA shows a decreasing trend, with high-value areas distributed in the pivotal cities for economic development. A total of 19.13 x 1010 CNY needs to be paid to compensate for ecological damage of the BTHUA. Uncertainty analysis shows that ECS is extremely sensitive to grassland footprint in most cities. Furthermore, environmental footprints as well as system dynamics considering multiple factors are still required for comprehensively evaluating the ecological environment quality and further exploring ecological compensation evaluation framework with incorporating various ecological service functions such as carbon sinks in the BTHUA. Findings can facilitate improving regional sustainability and provide a valid approach to determine ECS for the BTHUA and similar regions worldwide.