This study aims to evaluate the effectiveness of the Monarch Butterfly Biosphere Reserve (MBBR) in preventing forest degradation and land-use changes within communal lands in the context of limited public consultation and the transformation of communal forest governance. We analysed forest-cover changes over 50 years using a multi-temporal approach, integrating aerial photographs, orthophotographs and satellite imagery. We obtained contextual knowledge through our long-term research engagement with the region and interviews conducted during participatory fieldwork. We analysed land-use changes in a watershed within the MBBR in Mexico before and after its designation as a protected area. Despite the reserve’s protected status, nearly half of the study area experienced forest-cover changes. Surprisingly, the most intense deforestation occurred after conservation decrees, as some communities engaged in pre-emptive forest clearing in response to anticipated restrictions. However, in later periods, forest recovery – driven by payment for environmental services, natural regeneration and community participation – began to outpace degradation. Nonetheless, the fir forest that is essential for monarch butterfly habitat was reduced by 43.3%, with illegal logging being one of the leading causes. This study highlights the importance of community involvement when establishing protected areas, as it can help reduce environmental impacts and ensure conservation success.