Comparable species diversity and forest structure between sacred groves and protected forests reveal high conservation value of customary forests in Bali, Indonesia

Abstract

Abstract Sacred groves are forest patches managed and preserved by local communities to support their cultural and religious practices. Though often poorly documented, these forests provide refuge for threatened species and act as crucial nodes of biodiversity in an increasingly human-dominated landscape. Understanding the floristic and ecological characteristics of sacred groves, especially as compared to formally protected forests, is therefore key to their effective governance and incorporation into existing protected area network. In this study, we compared the tree diversity and forest structure of sacred groves and protected forests in Bali, Indonesia. We assessed the species richness, species diversity, basal area (or abundance) and community composition of trees from three ontogenetic stages (adults, saplings, and seedlings). Specifically, we focused our analysis on Dipterocarpus hasseltii, an endangered canopy tree species of local cultural significance. Sacred groves generally had similar levels of tree species richness, species diversity and demographic structure as protected forests at every ontogenetic stage, but differed significantly in community composition. Adult trees in sacred groves had a significantly higher basal area than that of protected forests. The population demography of D. hasseltii was similar in sacred groves and protected forests. We provide novel evidence that sacred groves that are managed to preserve a single tree species (i.e. D. hasseltii) could positively impact the conservation of other species, providing a similar conservation value as protected forests in terms of tree diversity and forest structure. Ultimately, our study supports the efficacy of social forestry and highlights its importance in biodiversity conservation.