How compound climate extremes reconfigure the urban development-ecological livability trade-off across China: A production possibility frontier perspective

The increasing frequency of unpredictable compound climate extremes makes finding trade-offs for COP 29 more complex. A crucial aspect in handling this complexity is understanding the competing priorities embedded in different policy options. In cities, this concerns trade-offs between extending urban development and securing ecological sustainability. However, there remains a lack of understanding how much compound climate extremes reconfigure these trade-offs and introduce spatial heterogeneity. To address the unknown, this study utilizes the Production Possibility Frontier (PPF) to show the trade-offs between urban development and ecological livability under compound climate extremes across China. The resulting PPF shows a nonlinear trade-off relationship. There are also multiple tipping points where the trade-offs drastically change across regions. Areas of higher exposure to extreme climate events are more vulnerable to systemic disruptions, indicating a reduced capacity to balance urban development with ecological livability. Meanwhile, under the influence of compound climate extremes, the national PPF becomes slightly steeper, while most regional PPFs show a downward and flattening trend in their second derivatives. This indicates that compound climate extremes moderately slow down the rise in marginal ecological opportunity cost. The inflection points where ecological opportunity costs begin to rise appear slightly later at the national scale but earlier in most regions, reflecting regionally differentiated resilience to climatic stress. Such differentiated trade-off patterns across regions imply complex interactions among development intensity, ecological resilience, and climate vulnerability. The findings will provide insights for sustainable urban development and region-specific climate adaptation strategies for China and also other countries facing similar climate and development challenges.