Informal conservation institutions and biodiversity protection: insights from sacred Kaya forests in Coastal Kenya

Understanding how different governance systems shape biodiversity outcomes is a central challenge in tropical forest conservation, particularly in regions where formal protection overlaps with long-standing community institutions. Tropical forests harbour a major proportion of the global biodiversity, while supporting ecosystem services, cultural values, and local livelihoods. Despite their importance, many tropical forests continue to decline under habitat destruction and overexploitation, raising questions about the effectiveness of different conservation governance models. While formal protected areas remain central to biodiversity policy, the role of informal community-based conservation institutions remains insufficiently examined and is still poorly understood. Here, we assess how informal conservation complements formal approaches by examining community perceptions of sacred forests as conservation institutions.  Using the sacred Kaya forests of southern Kenya as a case study, we conducted focus group discussions across five sites to analyse cultural, ecological, governance, and management dimensions of forest stewardship. Community members consistently valued Kaya forests for their role in maintaining habitat integrity, endemic species, and culturally significant medicinal plants. Informal conservation was perceived to provide fine-scale protection, high compliance, and resilience to local disturbances through culturally embedded rules, spiritual sanctions, and community stewardship. In contrast, formal conservation was associated with stronger legal protection and broader spatial coverage but was perceived as more vulnerable to illegal use and limited community engagement. These results highlight how informal governance institutions can enhance conservation effectiveness by reinforcing compliance and stewardship at local scales, complementing formal protected-area strategies. More broadly, this study contributes to emerging ecological and social-ecological theory by demonstrating how indigenous and community-based institutions can shape conservation outcomes and strengthen multi-level biodiversity governance in tropical forest systems beyond the focal region.