Global biodiversity and many of nature's contributions to people are deteriorating globally, with projections indicating continued deterioration unless concerted, effective efforts are made to reverse these trends. Protected areas (PAs) have long been regarded as cornerstones of conservation efforts, and in China, ecological function conservation areas are vital for the country's pursuit of ecological civilization. Globally and regionally, systematic conservation planning at different spatial scales is designed to identify conservation priorities and improve conservation coverage. Despite widespread attention to the outcomes of these conservation policies and actions, there is still an oversight in integrating ecological policies and spatial prioritization into the social-ecological system, thereby neglecting associated trade-offs and synergies between conservation benefits. This thesis aims to thoroughly assess the effectiveness of China's conservation policies within the social-ecological system and propose spatial prioritization strategies that consider complex trade-offs and synergies.

The thesis consists of three articles published or submitted for publication in international peerreviewed journals framed by an introductory chapter and joint conclusion. The first article reports on the first nationwide evaluation of the effectiveness of China's PAs in delivering multidimensional social-ecological outcomes. Using remote sensing and counterfactual analysis, the study finds that PAs increased net forest carbon storage by 13 % and water yield by 12 %, mitigated human footprint by 9 %, and reduced cropland productivity by 16 %. The study thus finds that PAs generally foster synergies and minimize trade-offs across various outcomes, with the notable exception of farming. It highlighted substantial regional and governance-level variations in the impacts of PAs, emphasizing the need for context-specific, evidence-based solutions to harmonize conservation efforts with human well-being, especially in the face of potential conflicts in social-ecological outcomes.

The second article evaluates the effectiveness and spillover effects of the Gutianshan National Nature Reserve (GNNR) in Kaihua County, China, in mitigating forest degradation, loss, and carbon emissions. Employing a combination of counterfactual analysis and remote sensing observations, the study demonstrates that GNNR remarkably reduced forest degradation, forest loss, and forest carbon emissions by 78.56 %, 95.54 %, and 97.01 %, respectively, with these benefits extending to adjacent buffer zones. However, it also uncovered 'leakage' of forest carbon emissions in buffer zones. The study noted variations in effectiveness and spillover effects depending on baseline geographical conditions. Leveraging this heterogeneity, it identified spatial conservation priorities across 35.64 % of Kaihua County for optimal forest conservation effectiveness. This research thus contributes to better design of area-based conservation strategies, guided by outcome-based evidence, aiming to support the 30 × 30 conservation target regionally.

The third article investigates interactions between ecosystem services (ESs) across various spatial and temporal scale dimensions, aiming to inform sustainable spatial planning and conservation strategies for regional ecological function zoning. The study involved mapping six ESs, analyzing their trade-offs and synergies, and identifying primary drivers and distinct ES bundles. It found spatially heterogeneous patterns of ESs, notably a decrease in food production and an increase in water supply. The analysis identified ten ES pairs exhibiting synergies and five pairs, primarily related to food production, showing trade-offs at different scales. The study also revealed variations in drivers and ES bundles across spatial and temporal scales. Building on social-ecological drivers of ESs and ES bundles, the study proposed ecological functional zoning and spatial management strategies at both grid and sub-watershed scales and also identified ES pairs with declined synergies as an additional priority in ecosystem management. By integrating spatial-temporal and cross-scale insights into ES interactions, this research contributed to the development of sustainable ecosystem management practices across scales.

Overall, this thesis presents an in-depth study of nature conservation and ecosystem management from a broad national perspective to detailed regional case studies. It enhances our understanding of the overall impacts and effectiveness of conservation actions, offering specific, actionable strategies for setting conservation priorities within social-ecological systems. This work provides researchers and policymakers with a robust framework for evaluating and prioritizing conservation efforts, bridging the gap between theory and practical application in ecosystem management.