Economic analysis on carbon sequestration through optimal stochastic control model for forest resources management under uncertain environments.

自1997年京都峰会以来，相应的国家开始通过减少大气中的二氧化碳含量来解决全球变暖问题。在日本，政府同意将3.9%的减排目标分配给森林部门的活动。另一方面，私营林业部门正在为这种减少的目的实施排放交易。虽然这些减少的活动得到了很大的注意，但重新种植和/或减少的活动往往被放弃。也就是说，如果不实行林业做法，森林所引起的这种固碳功能可能就不明显。在这种放弃现象的背后，可能有一个事实，即森林所有者面临未来产品价格下降和价格不确定，这可能会阻碍他们的管理积极性。在本研究中，我们首先在实地调查的基础上，对森林活动从种植、采伐到伐木进行了碳平衡分析，并开发了一个统计程序来估计森林林分的碳固存量。在此基础上，通过补贴政策下林分经营优化框架进行碳评价。评价方法基于影子价格法。上述碳分析是基于林分可持续经营的假设。然而，由于森林所有者面临管理的经济不确定性，我们下一步寻找维持管理的最低门槛价格。如果知道这个价格，就可以实施可持续管理，通过某种政策来填补所得的阈值和市场价格之间的差距，就一定可以实现林分的上述固碳功能。

Since the Kyoto Summit in 1997, the corresponding nations started to tackle the global warming problem by reducing the level of carbon dioxide from the atmosphere. In Japan, the government agreed to allocate 3.9% of the pursued reduction to forest sector activities. On the other hand, the private sector of forestry is implementing the emission trading for such a purpose of reduction. While these activities for the reduction have been paid a great deal of attention, replantation and/or thinning activities are tended to be abandoned. That is, if no forestry practices were implemented, such a function of carbon sequestration induced by forests might not be apparent. Behind this phenomenon of the abandonment, there might be a fact that forest owners face future reduction of product price as well as price uncertainty, which could discourage their management incentive.In this research, we first conducted carbon balance analysis on forestry activities from plantation, harvesting, to lumbering based on our field survey and developed a statistical procedure to estimate the amount of carbon sequestered in a forest stand. Following this analysis, carbon evaluation was conducted through the optimization framework on forest stand management under the subsidy policy. Evaluation method was based on the shadow price approach. The above analyses on carbon were based on the assumption of the sustainable forest stand management. However, since forest owners face to economic uncertainty for the management, we next searched for a minimum threshold price to sustain the management. If such a price were known, the sustainable management could be implemented and the above function of carbon sequestration by forest stands becomes sure to be attained by filling a gap between the derived threshold and market prices by some kind of policy.