Mapping urban energy–water–land nexus within a multiscale economy: A case study of four megacities in China

Energy, water, and land (EWL) are typical elements in urban food-energy-water systems. With the expansive growth of urbanization and the economy, the demands for EWL keep increasing and pose significant challenges to urban sustainability. Previous studies mostly focused on one or two elements flows through sectoral approaches while ignoring the interconnectedness of food-energy-water subsystems and the complexity of an open urban system. Here, we adopted a nexus view to track the urban EWL flows not only within local but also across regional, national, and even global supply chains from the production- and consumption-based perspectives using the environmentally extended multiscale input-output model (EE-MSIO). The four Chinese municipalities (i.e., Beijing, Tianjin, Shanghai, and Chongqing), also known as megacities, were selected as our cases. Our results revealed that all four megacities were consumption-oriented cities for EWL resources. Nearly 72%–77%, 87%–92%, and 95%–99% of the consumption-based energy, water, and land flows were sourced from outside the geographical boundaries of Beijing, Tianjin, and Shanghai, respectively. Domestic regions were the major suppliers for the four megacities. This analysis can help policy-makers to develop more effective and targeted strategies for complicated urban ecological resources management.