Impact assessment of dam construction and forest management for Japanese macaque habitats in snowy areas
Japanese macaques (Macaca fuscata) in their northernmost habitats represent a keystone species and play a central role in heavy snowfall ecosystems. However, distributions have been restricted by pre-war hunting, and populations are facing issues of natural forest losses caused by new dam constructions and massive conifer plantations. In the present study, we predicted the influences of these environmental conditions on macaque habitats during each season, and evaluated the effect of natural forest restoration as a mitigation measure. We constructed multiple habitat suitability models on the basis of different forest change scenarios, by using maximum entropy modeling (Maxent). We predicted the influence of each scenario by calculating the habitat unit (habitat quality × habitat quantity). We made the following predictions: (1) the influences of environmental conditions on habitat models vary seasonally, but dam construction destroys the optimum macaque habitats in every season; (2) restoration of conifer plantations to semi-natural forests does not always contribute to the improvement of total habitat unit, except in snowy seasons; and (3) in comparison with encouraging natural forest restoration in plantation areas and maintaining the standard-rotation plantation management, the implementation of long-rotation plantation in existing plantation areas provides more suitable alternative habitats for macaques in non-snowy seasons.