Suchergebnisse

A dynamic model for fishery resources with predator–prey relationships is constructed based on observational data and research findings for Lake Kasumigaura, Japan. The analysis of the stationary state as well as the sensitivity analysis shows that the use of diesel-powered trawling, which enables the large-scale catch of prey species in comparison with the traditional method of sailing trawling, may lead to the extinction of predator as well as prey species once the trawling efficiency in the catch of prey species is improved beyond the present level, provided that fishermen behave so as to maximize their profits subject to the restriction of operation time.

The paper contains an analysis of dynamic aspects of environmental damage in an open multisector economy, where the factor intensity and the pollution intensity of each sector are different, and the stock of pollutants is assumed to affect adversely the total amount of one production factor. The paper clarifies the role of substitution relationships among production sectors as well as production factors in enlarging environmental damages as the consequence of the intertemporal maximization of gross regional product.

A theoretical model of the sewage treatment plant location problem is presented, based on the assumptions of a homogeneous space and a homogeneous channel geometry of a river running parallel to a one-dimensional region. The analytical structure of the model is discussed. The model is then applied to the specific case of a suburban region of the Tokyo Metropolitan Region, where both the homogeneity assumptions are dropped. The numerical simulations show clearly how the heterogeneity in population distribution and river characteristics, as well as the trade-off ratio between water quality and least cost expenditure, affects the optimal plant locations.

In development regions, the management of environmental quality and the regional planning of water supply and the disposal of residuals are closely related to the form of intraregional population distribution. In this paper a hierarchical programming model is presented of the optimum intraregional population distribution in relation to environmental quality and the economic cost of water supply and the disposal of residuals. The model is applied to the specific case of a suburban region of the Tōkyō Metropolitan Region. The results show that the higher-order objective of environmental quality regulates the spatial allocation of disposal-of-residuals activities, and the lower-order objective of economic cost determines the form of intraregional population distribution.