Do establishment of protected areas and implementation of regional policies both promote the forest NPP? Evidence from Wuyi Mountain in China based on PSM-DID

Establishing protected areas has been a longstanding strategy to conserve forests. Net Primary Productivity (NPP) offers a reflection of ecosystem quality and vegetation vitality compared to traditional spatial indicators, making it a valuable metric for evaluating conservation outcomes in protected areas. Additionally, there is a lack of knowledge about the concurrent influence of in situ conservation and pertinent policies on forest conservation. Through Propensity Score Matching (PSM) and the Difference-in-Difference (DID) model, we evaluated the conservation outcomes of NPP within protected areas and identified different policies’ impacts. Wuyi Mountain in China, known for its rich forest resources, was selected as the study area. The results revealed: (1) NPP within all protected areas fluctuated within a stable range from 1985 to 2021, with some exhibiting a significant upward trend; (2) A total of 62.5 % of protected areas demonstrated a positive effect on forest NPP. There is a 72 % effective conservation rate for nature reserves, one type of protected area in China, making them the most effectively protected in Wuyi Mountain; (3) In 50 % of the cases, the policies resulted in positive outcomes. The impact of policies on forest NPP varies across different types of protected areas; (4) Only 16.67 % of policy scenarios demonstrated a concurrent positive effect from both protected areas and conservation policies. By analyzing the impact of protected area establishment and conservation policy implementation on NPP, our research can offer valuable insights for policymakers aiming to enhance forest conservation in mountain areas. • the PSM-DID methodology was suited for assessing the conservation outcomes. • 62.5 % of protected areas in Wuyi mountains effectively conserved forests during 1985–2021. • Temporal dynamics (1985–2021) of NPP inside and outside protected areas were unveiled. • Policy impact differed among different types of protected areas.