実態調査に基づく広島県における森林資源の需給分析

アンケート調査に基づく動態分析と森林資源量の将来推計

抄録

 In this study, a life-cycle flowchart of wood resources in Hiroshima Prefecture was developed through questionnaire surveys, and based on the flow analysis, long-term availability of local wood was estimated. Subsequently, issues related to utilization/consumption of the wood and forest renewal strategies were discussed. Our findings revealed that because of the recent supply-demand imbalance in local wood, Hiroshima will possibly fall short of wood resources in the near future. The discussion is based on the following.

 1) Material flow analysis
 Material flow analysis, which focused on the wood resources in Hiroshima Prefecture, was based on a questionnaire survey (173 associations) and interviews with seven associations. The results revealed that while a significantly small percentage of local wood is used as material, most of it is processed in lumber mills and sold outside the prefecture, and that most of the wood chips obtained are used for papermaking.

 2) Increasing demands for wood chips
 The questionnaire survey revealed that wood chip demands for the purpose of power generation would most likely show a rapid increase in the future: It may increase to 300 thousand tons in five years, which is three times the present demand.

 3) Dynamic analysis of the change in wood chip demands
 Based on the survey results, the changes in wood chip demands were estimated: In the coming 45 years, if wood chip demand levels remain constant, a 10% increase in the amount of local wood resources is likely, while around a 20% drop in the available wood resources is expected, if the wood chip demand rises.

 4) Dynamic analysis of municipality differences
 In Hiroshima Prefecture, the amount of resources and reforestation practices etc., are significantly different for each municipality. Therefore, the amount of local wood resources was estimated based on a dynamic analysis. The results show that an area with large wood stocks in its forests may experience a significant decrease in its wood stock because of a greater demand by 2100. Therefore, in such areas, reforestation will be necessary.

 Hiroshima has diverse forests and the total area of its forests is largest among all the prefectures in western Japan. Naturally, life-cycle management for healthy forests has been of great interest for its citizens. Recently, however, a major surplus has been caused by insufficient self-consumption of local wood. In response to this supply-demand imbalance, various efforts have been focused at promoting home-utilization and -consumption, including some successful cases, such as its redirected use as a new form of energy source. Nevertheless, as the results of this study suggest, if such one-way promotion is carried out without careful, scientific monitoring, wood resource would likely fall short in the near future. It should also be noted that in some areas, wood resources have shown a decreasing tendency in all the forests. Therefore, managing the local wood resources in Hiroshima Prefecture is more difficult than it seems. Our findings also suggest that any measures for healthy forest management must be undertaken after carefully considering site specific differences.