Models of Deforestation with Spatial Dependency by Human Population Interactions

概要

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Deforestation is a result of complex causality chains in most cases. But identification of limited number of deforestation factors shall provide comprehensive and general understanding of the vital phenomenon at a broad scale, as well as projection to the future. Two factors-human population size (N) and relief energy (R: difference of minimum altitude from the maximum in a sampled area)-were found to give sufficient elucidation of deforestation by a nonlinear regression model, whose functional forms were suggested by step functions fitted to one-kilometer square grid-cell data in Hiroshima Prefecture, Japan (n=8697). Thus let forest areal rate on the same cell areas be F≡F(N, R), 0≤F≤1.<BR>We examine various nonlinear regression models having error terms with spatial dependency through the real data. Then, a model with five parameters was selected by AIC.<BR>It is expected that the parameters of a developing country and those of a developed country are different. Hence, the parameters should be useful as effective environment indicators.