A Method to Weigh the Transfer of Eco-Environmental Pressure for Regional Sustainability

Human activities can not only impose local pressures on the eco-environment, but also cause indirect impacts in other regions through material flows associated with interregional trade. It is crucial to understand this interregional human–nature interaction to achieve regional sustainable development. This study proposes using human-harvested net primary productivity (NPP) as a metric to quantify the transfer of eco-environmental pressure. Taking the Yangtze River Economic Zone (YREZ) in China as an example, this study examines the transfer of human-harvested NPP and eco-environmental pressures among different provinces through trade. Specifically, we first compile provincial agricultural and forestry statistics to calculate human-harvested NPP. Next, we embed these values into an environmentally extended multi-regional input–output (EE-MRIO) model to trace the flow of human-harvested NPP. A simple index of eco-environmental pressure (EEP) is then constructed. The flow direction—and thus the associated eco-environmental pressure—is analyzed using a gravity transfer model. Our findings show that the human-harvested NPP in the YREZ ranged between 0.036 GgC/km2 and 0.211 GgC/km2. A strong correlation was found between the EEP index and total permanent population per unit land area (R = 0.764, p = 0.006, N = 11). Furthermore, significant correlations were observed between the changes in EEP (before and after harvested NPP flow) and total permanent population per unit land area (R = −0.912, p = 0.000, N = 11), as well as between EEP changes and total GDP per unit land area (R = −0.927, p = 0.000, N = 11). Specifically, human-harvested NPP was relatively high in economically developed regions, such as the downstream provinces of the YREZ, indicating substantial natural resource and eco-environmental pressures in those areas. However, these pressures can be transferred to other regions through the flow of human-harvested NPP via interregional trade. Considering the YREZ as a whole, the gravity centre of eco-environmental pressure shifted from the northeast to the southwest. This study highlights the need to enhance efforts toward understanding regional sustainability from a holistic perspective.