A systematic review of deforestation outcomes in potential other effective area-based conservation measures across...

Recognizing conservation contributions from areas outside protected areas (PAs), including other effective area-based conservation measures (OECMs), is increasingly central to meeting global biodiversity targets. However, little is known about which areas could qualify as OECMs and whether they support forest conservation. Focusing on Latin America, we conducted a systematic literature review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines synthesizing 93 peer-reviewed studies published through 2024 that assess the effectiveness of OECMs outside formal PA systems in reducing deforestation. First, we identified and classified area-based measures that may qualify as potential OECMs into six types based on their conservation objectives and characteristics: strict biodiversity conservation areas, set-aside areas for ecosystem services, Indigenous peoples' territories, local communities' territories, other managed sustainable-use areas, and ancillary conservation areas. Second, we synthesized the available evidence on their effectiveness in reducing deforestation. Indigenous people's territories were the most frequently evaluated, whereas strict biodiversity conservation areas have received relatively little attention. Methodologically, most evidence relied on nonexperimental comparisons of forest-cover trends; quasi-experimental designs were less common but provide stronger causal inference of conservation effectiveness. Disaggregating outcomes by comparator type revealed important patterns: Indigenous territories most consistently showed reduced deforestation relative to both PAs and non-PAs, whereas local communities' territories showed more favorable outcomes relative to non-PAs than to PAs. Set-aside areas for ecosystem services showed predominantly negative outcomes, largely reflecting weak enforcement. Despite this evidence base, very few of these areas have been formally recognized as OECMs, highlighting a disconnect between available research and reporting under the Kunming-Montreal Global Biodiversity Framework. Bridging this gap will require stronger causal evidence, broader geographic coverage, and inclusive recognition processes that account for the governance rights of those who manage these territories.