Relative effects of sacred forests and protected areas on forest conservation and structure in Japan

Sacred forests, found on all inhabited continents, are globally recognized for their biodiversity and conservation value and their role in cultural landscapes. Assessments of the effects of forest sacredness have mostly focused on small regions and are based on diverse methods. We used geographic information provided by the public and datasets derived from remote sensing to locate and examine changes in shrine and temple forests across Japan. We compared the aboveground vegetation structure and annual rate of forest loss of these sacred forests with their surrounding nonsacred forests and with legally protected areas. We tested whether these differences were comparable between urban and rural areas and between shrine and temple forests. Based on a sample of 35,899 sacred forests, sacred forests had higher canopy height (mean [SD] = 15.5 m [0.02] vs. 15.2 m [0.01], t test, p < 0.001) than the surrounding nonsacred forests. An annual rate of sacred forest loss was 50% lower than other forests outside legally protected areas (0.07%/year and 0.13%/year, respectively) from 2000 to 2022. Sacred forests had forest loss rates comparable to strictly protected forests (0.05%/year for International Union for Conservation of Nature categories Ia-III), and sacredness and legal protections cumulatively reduced forest loss. The protection sacred forests offer was confirmed across urban and rural areas of Japan. Large-scale assessments of sacred forests' efficiency are now possible based on geographic information provided by the public. We found that sacred forests were as effective as strict legally protected areas at preventing forest loss and that shrine and temple forests were important features of lowland urban and rural landscapes of Japan, ranging from boreal to subtropical forests. These sites need to be further considered in national or even international conservation frameworks.