Assessing CO2 Reduction Effects Through Decarbonization Scenarios in the Residential and Transportation Sectors: Challenges and Solutions for Japan’s Hilly and Mountainous Areas

Depopulation, aging, and regional decline are becoming increasingly serious issues in Japan’s hilly and mountainous areas. Focusing on mitigating environmental damage and envisioning a sustainable future for these regions, this study examines the potential for reducing CO2 emissions in the residential and transportation sectors by 2050. Bottom-up simulations were used to estimate CO2 emissions. Subsequently, six decarbonization scenarios were formulated, considering various measures from the perspectives of population distribution and technological progress. Based on these scenarios, this study analyzes changes in future population, energy consumption, and CO2 emissions by 2050. The results of this study show the following. (1) Depopulation and aging problems in these regions are expected to become more severe in the future. It is necessary to take action to promote sustainable regional development. (2) Pursuing decarbonization has a positive impact on enhancing regional sustainability; however, maintaining the intensity of measures at the current level could lead to a reduction of only 40% in CO2 emissions per capita by 2050 compared with 2020. (3) Scenarios that strengthen decarbonization measures could achieve a reduction of over 95% by 2050, indicating that carbon neutrality is attainable. However, this will require implementing measures at a higher intensity, especially in the transportation sector.