Can coastal plantation forests substitute for natural coastal forests as bird and plant habitat? A test across coastal zonation

Natural forests are increasingly being replaced by plantation forests, highlighting an urgent need to reconcile forest use and biodiversity conservation. Coastal forests serve as refugia for species of conservation concern, but they have been globally replaced by plantations, and conversion remains ongoing. As natural coastal forests become increasingly scarce, opportunities for direct biodiversity comparisons with coastal plantations are also disappearing. This scarcity leads to underestimation of the conservation value of natural coastal forests, while effective management measures to conserve biodiversity within coastal plantations remain poorly developed. By focusing on the largest natural coastal forests in Japan, we assessed whether plantation coastal forests can substitute for natural coastal habitats across multiple taxonomic groups, functional groups, and threatened species. We found that plantations supported bird species richness comparable to natural forests at the community level and for threatened species. Surveyed plantation forests supported 7% of global breeding populations of the endangered Brown Shrike. However, plantations hosted lower forest plant species and higher introduced plant species richness. Plantations also significantly altered coastal zonation patterns in plant communities: forest species distribution shifted seaward, whereas coastal and introduced species shifted landward. Coastal plantations are unlikely to be complete substitutes for natural coastal forests for plant species, yet still have the potential for restoring historically lost coastal forest ecosystems. Confining further plantation activities to landward areas and plantations with low canopy cover will mitigate the negative impacts of plantations and further conserve unique coastal communities where forest and grassland species can coexist.