Evaluating future habitat quality responding to land use change under different city compaction scenarios in Southern China

Rapid urban expansion, accompanied by intense landscape changes, significantly affects natural habitats. Promoting sustainable urban development, such as the compact city strategy, is essential to balance ecosystem conservation and socio-economic development. Previous studies have generally focused on exploring the ecosystem impact of urban expansion concerning the future projections of climate, population, and economic development. Less attention has been paid to how different urban forms modify the landscape and affect habitats at a fine resolution. This study has built a framework to demonstrate future land use change under various city compaction scenarios using a bottom-up Cellular Automata (CA) model and a top-down Markov model. Then the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model was incorporated to evaluate the resultant habitat quality. By taking the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) as the study area, three future compact city scenarios in 2040 and 2060 were proposed to examine the accumulative effect of urban growth. The results show that by 2040, the high-compact scenario will cause the highest habitat quality degradation among all scenarios due to marked cropland displacement induced by urban edge expansion. By 2060, intensified medium or low-compact scenarios tend to create new urban clusters outside the existing urban areas, resulting in severe habitat isolation and fragmentation. The GBA presents significant spatial heterogeneity in habitat quality variation because of the uneven development between the core and key node cities. Our results suggest that a collaborative strategy should be promoted to motivate the unique advantages of each city. This could include maintaining the amount and connectivity of open space under city integration processes and reserving high-quality cropland, such as fish-pod-based agriculture, to mitigate habitat quality degradation. This study can provide insights for developing long-term land use management when applying compact city strategies to balance ecological conservation and urban development needs.