General trends in research using impact evaluation methods on the effectiveness of terrestrial protected areas in...

Protected areas (PAs) are primary biodiversity conservation instruments under the Convention on Biological Diversity (CBD). Despite a substantial body of research assessing their causal impact, a comprehensive global synthesis remains lacking. This study examines trends in PA effectiveness on biodiversity loss using impact evaluation studies published between 2000 and 2023. From 129 identified studies, matching emerged as the predominant method, with deforestation and forest cover as the most frequently assessed outcomes. Notably, none of the reviewed studies incorporated CBD-approved biodiversity indicators, such as the Red List Index, and only one applied the Biodiversity Intactness Index (BII) established by the Kunming-Montreal Global Biodiversity Framework. These findings underscore the need for future research to integrate standardized biodiversity metrics as outcome variables. Methodological advancements in impact evaluation are equally essential to strengthen conservation policy assessments and support evidence-based decision-making within international biodiversity agreements.