Navigating trade-offs in urban nature restoration: spatial prioritization of brownfield greening for supporting multiple targets of the Kunming–Montreal Global Biodiversity Framework in a high-density city

Brownfield greening (BG) offers a strategic spatial opportunity to support the Kunming–Montreal Global Biodiversity Framework (KMGBF) in urban contexts, particularly Target 2 on ecosystem restoration. However, how different spatial prioritization strategies for pursuing this restoration objective may influence other urban-relevant targets, such as Target 11 (nature’s contributions to people) and Target 12 (urban greenspace access), remains underexplored. This study developed six brownfield greening scenarios based on different planning objectives and prioritization logics and assessed their contributions to selected KMGBF targets in Guangzhou, a high-density city in China. The results suggest markedly different spatial outcomes across scenarios. Based on the scenario comparison, human-centered targets (Targets 11 and 12) were more often advanced together, whereas connectivity oriented restoration (Target 2) was less consistently aligned with these human centered targets. Among the tested scenarios, a balanced efficiency scenario provided a useful intermediate pathway, retaining over 80% of the maximum tested performance for Targets 11 and 12 while maintaining approximately 60% of the highest observed connectivity gain for Target 2. Overall, this study offers a scenario-based planning framework for exploring how alternative BG strategies may support selected KMGBF targets in land-constrained cities. By making potential trade-offs and synergies more explicit, the framework can inform biodiversity-inclusive spatial planning (Target 1), support more transparent urban restoration decision-making, and facilitate public communication and participation in restoration planning (Target 14).