Clearcut areas aged 2-6 years in shelterbelts support high diversity of butterflies and flowering plants, including endangered grassland butterflies, in the Tokachi District of Hokkaido, northern Japan

Grassland butterflies are declining widely in temperate regions, and are thus a key target for conservation. Recent studies have shown that forest clearcuts can be temporary habitats for these species. Shelterbelts - rows of trees, planted to protect houses and crops from the winds - are periodically cleared. This clearing is necessary to prevent falling large branches from mature trees while maintaining their primary function. Consequently, recently cleared young shelterbelts have the potential to serve as habitats for grassland species. However, it remains unclear how long young shelterbelt plantations support grassland butterflies. In this study, we made a survey where the responses of flowering plants and butterflies to plantation age and environmental parameters were investigated during spring and summer in eight plantations aged 2-12 years. Plant richness, nectar abundance, as well as butterfly richness and abundance decreased with increasing plantation age. Butterflies, including endangered species, thrived in 2-6-year plantations, but declined dramatically thereafter. Age-related environmental variables, particularly canopy openness, explained the decline in plants and butterflies, with age being a more important factor than environmental variables. These results indicate that regenerated shelterbelts aged 2-6 years function as habitats for grassland butterflies, and that plantation age can be used as a simple indicator of habitat quality for such species, including endangered ones. Given that young plantations persist as grassland butterfly habitats for only 6 years since planting, a new clearcut needs to be created within the dispersal range for butterflies to help build metapopulations and ensure their conservation at a landscape scale.