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水平来解决全球变暖问题。在日本，政府同意将所追求的减少量的3.9%分配给林业部门的活动。另一方面，私营林业部门正在实施排污权交易，以达到这样的减排目的。虽然这些减少的活动受到了极大的关注，但补种和/或间伐活动往往会被放弃。也就是说，如果没有实施林业实践，森林引起的碳固存的这种功能可能不明显。在这种被遗弃的现象背后，可能存在着一个事实，即森林所有者面临着未来产品价格的下降以及价格的不确定性，这可能会阻碍他们的经营激励。在本研究中，我们首先在实地调查的基础上，对从人工林、采伐到伐木的林业活动进行了碳平衡分析，并开发了一个统计程序来估计森林中的碳固存数量。在此基础上，通过补贴政策下的林分经营优化框架进行了碳素评价。评估方法基于影子价格法。上述对碳的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着经营的经济不确定性，我们接下来寻找维持经营的最低门槛价格。如果知道这样的价格，就可以实施可持续经营，通过某种政策填补衍生门槛与市场价格之间的差距，就一定能够实现森林固碳的上述功能。

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.