Simulating forest transition for sustainable forestry planning in Japan: A backcasting model of roundwood supply and carbon stocks with operational and regional considerations

Forests are essential for global ecological stability, carbon balance, and the sustainable supply of roundwood resources. Forests in Japan are undergoing a policy-driven transition aimed at enhancing forest health and roundwood supply. This study presents the Forest Management Model for Cyclical Forestry (FM2-CF), a backcasting simulation model designed to support this transition over a 100-year horizon. The model integrates forest structural factors, forestry operational factors, and regulatory factors to investigate the long-term implications regarding Japan’s forest resources under the transition. It characterizes the national age-class transition of single-storied forests, quantifying roundwood supply and CO 2 fixation potential. Regional analyses across all 47 prefectures reveal pronounced spatial disparities in forest resources, indicating the necessity of localized strategies. In addition, FM2-CF evaluates the required forestry operational efforts measured by forest area, labor force, and cost. The simulated forestry management has revealed a shift of operational focus from reforestation and weeding in the early stages toward more balanced harvesting and thinning activities in matured forests. Scenario-based projections of roundwood supply–demand dynamics have highlighted surpluses and shortfalls across regions and time. Our results provided insights into the sufficiency and timing of supply relative to evolving policy-related utilization demand. While the model is primarily structured as a supply-side strategic planning tool, it provides a valuable roadmap for aligning long-term forest renewal with sustainable management practices and assessing policy feasibility. Future extensions may incorporate growth modeling and demand-side mechanisms to improve applicability across broader contexts and other countries.