堀江 哲也

After the reversion of Okinawa (Ryukyu Islands) to Japan in 1972, extensive urban and agricultural development resulted in a significant increase in sediment discharge to coastal waters. The release of sediment has caused the degradation of freshwater and coastal ecosystems and biodiversity. A consideration for catchment-to-reef continua, as well as agricultural (socioeconomic) factors is necessary to establish proper land-based management plans for the conservation of the island environment. We have set up a framework to integrate biophysics and socioeconomics: 1) setting a conservation target and threshold, 2) identifying the sources and processes, and 3) examining cost-effectiveness and management priorities. The framework may be applicable to other tropical and subtropical islands with similar characteristics.

Cost-effective strategies are needed to find and remove diseased trees in forests damaged by pathogens. We develop a model of cost-minimizing surveillance and control of forest pathogens across multiple sites where there is uncertainty about the extent of the infestation in each site and when the goal is to minimize the expected number of new infections. We allow for a heterogeneous landscape, where grid cells may be differentiated by the number of trees, the expected number of infected trees, rates of infection growth, and costs of surveillance and control. In our application to oak wilt in Anoka County, Minnesota, USA, we develop a cost curve associated with saving healthy trees from infection. Assuming an annual infection growth rate of 8%, a $1 million budget would save an expected 185 trees from infection for an average of $5400 per tree.We investigate how more precise prior estimates of disease and reduced detection sensitivity affect model performance. We evaluate rules of thumb, finding that prioritizing sites with high proportions of infected trees is best. Our model provides practical guidance about the spatial allocation of surveillance and control resources for well-studied forest pathogens when only modest information about their geographic distribution is available. © 2012 Elsevier B.V.

Using a multi-region and multi-sector computable general equilibrium model, this paper evaluates the border adjustment policies of carbon regulations in Japan. We consider five types of border adjustments and examine their effects on the welfare, carbon leakage, and competitiveness of the Japanese energy-intensive trade-exposed (EITE) sectors. Our analysis shows that no single border adjustment policy is superior to the other policies in terms of simultaneously solving three primary issues: Welfare degradation, carbon leakage, and a loss of competitiveness in the EITE sectors. In addition, we show that export border adjustments are effective at restoring the competitiveness of Japanese exporters and reducing leakage. Our analysis also reveals that border adjustment in Japan significantly affects carbon leakage to China and the competitiveness of the iron and steel sectors. Finally, we show that border adjustments with and without consideration of indirect emissions have similar impacts, which indicates that the information regarding direct emissions is sufficient for implementing border adjustment in Japan.

We model optimal detection of sub-populations of invasive species that establish ahead of an advancing front. For many invaders, eradication of the main population is an untenable goal, yet it may be possible to treat and eradicate emerging sub-populations once these sub-populations are detected. We embed a dynamically optimal post-detection management plan of sub-populations into a model of optimal detection effort determination and find that optimal detection effort depends, in part, on the distance from the main front: locations closer to the front with shorter management horizons enjoy lower reductions in overall cost from intervention. The uninfested landscape is divided into two zones, characterized by different dynamically optimal management plans: a suppression zone and an eradication zone. In the suppression zone, optimal detection effort increases with distance from the front. At the distance where the suppression zone yields to the eradication zone, optimal detection effort plateaus at its maximum level. (C) 2011 Elsevier B.V. All rights reserved.

Economic assessment of damage caused by invasive alien species provides useful information to consider when determining whether management programs should be established, modified, or discontinued. We estimate the baseline economic damage from an invasive alien pathogen, Ceratocystis fagacearum, a fungus that causes oak wilt, which is a significant disease of oaks (Quercus spp.) in the central United States. We focus on Anoka County, Minnesota, a 1,156 km(2) mostly urban county in the Minneapolis-Saint Paul metropolitan region. We develop a landscape-level model of oak wilt spread that accounts for underground and overland pathogen transmission. We predict the economic damage of tree mortality from oak wilt spread in the absence of management during the period 2007-2016. Our metric of economic damage is removal cost, which is one component of the total economic loss from tree mortality. We estimate that Anoka County has 5.92 million oak trees and 885 active oak wilt pockets covering 5.47 km(2) in 2007. The likelihood that landowners remove infected oaks varies by land use and ranges from 86% on developed land to 57% on forest land. Over the next decade, depending on the rates of oak wilt pocket establishment and expansion, 76-266 thousand trees will be infected with discounted removal cost of $18-60 million. Although our predictions of removal costs are substantial, they are lower bounds on the total economic loss from tree mortality because we do not estimate economic losses from reduced services and increased hazards. Our predictions suggest that there are significant economic benefits, in terms of damage reduction, from preventing new pocket establishment or slowing the radial growth of existing pockets.

Sound economic assessments of damages caused by exotic invasive species provide a basis to determine whether management programs should be established, modified, or discontinued. Few analyses have attempted to carefully quantify those damages, especially for forest pests. Oak wilt is the most significant disease of oaks (Quercus spp) in the north central United States and is caused by a nonnative fungus, Ceratocystis fagacearum.

Though there are many studies on Japanese agricultural productivity, studies in relation to efficiency of Japanese agriculture are very few. In this study an attempt is made to measure the technical efficiency and technical change in Japanese agriculture from 1965 to 1995. Both data envelopment analysis (DEA) and stochastic frontier analysis (SFA) methods are used to measure the efficiency. We obtained a consistent result between these two analyses. We also found that a fair amount technical progress existed, but at the same time technical efficiency declined in these thirty years. Prefectures which have large-scale rice farming such as Hokkaido, Niigata, Ishikawa, and Toyama possess high technical efficiencies. Also, prefectures which are near big cities such as Tokyo, Kanagawa and Aichi possess high technical efficiencies. On the other hand, cold, mountainous and less populated prefectures such as Iwate, Tottori and Shimane possess low technical efficiencies. Also, we found that technical efficiency diverged rather than converged over these 30 years.