Land–Water–Energy Coupling System and Low-Carbon Policy Simulation: A Case Study of Nanjing, China

Global climate change produces large amounts of CO2, and carbon emission reduction has become a global hot topic. As a key city in the Yangtze River Economic Belt, Nanjing plays a significant representative role in the process of achieving the “double carbon” goals. In this paper, a land–water–energy coupling system was established and urban carbon emissions were estimated. Through the SD model, the future urban carbon emissions were predicted under the adjustment of different land, water and energy consumption scenarios. We studied the relationship between urban carbon emissions and the land–water–energy coupling system, and whether Nanjing can achieve carbon neutralization in 2060 under conditions of natural development. The results show that urban carbon emissions in Nanjing have reached a peak in 2018, but low carbon measures are still needed for Nanjing to achieve its goal of carbon neutrality by 2060. Specific measures include increasing investment in technological innovation, expansion of the application scope of clean energy, reasonably planning land use structure, water conservation and wastewater utilization and the application of advanced carbon utilization technology. The results in this paper can serve as a reference for other cities and provide guidance for future urban planning and decision making.