都市近郊農業地域における平地林の減少要因

Abstract

In suburban agricultural area, woods called as ‘Heichirin’ have been maintained on the strong tie with agriculture and rural lifestyle, but today deforestation is occurring with changing agricultural structure and urbanization. This study analyses decreasing woods in Ami-town (Ibaraki Pref.) for 20 years and identifies factors influencing this phenomenon. Ami-town is a plain village and its land has increasingly become residential and industrial in recent years. Area of woods is diminished by about 170 hectare in the 20 years between 1970 and 1990. The diminishing rate is remarkably high especially in urbanization promotion area.In order to analyse determinants of diminishing woods, first, the 42 settlements in Ami-town are classified into 4 groups according to their socio-economic conditions as of 1970; Groupl is an agricultural district, Group2 has a large residential area in early times, Group3 has a large industrial area in farmland, Group4 is a developed area.Second, on the ground of the above classification, we analyse correlation between changein socio-economic condition and diminishing rate of total area of woods in each settlement. Then three changes in condition are pointed out; (1) Development in agricultural side in 1960's, (2) Conversion of woodsinto industrial park and increase in farmers with a side job, (3) Population growth since 1980.Third, multiple regression analysis is used in order to find the factors in each forest unit's character. We examine positive and negative correlation between the vanished forest units and their characters. Mainly, factors such as designation of specific areas (urbanization promotion area), spatial mass (larger scale), road accessibility (nearer to the roads) and topographical condition (artificial landform) have positive correlation.In conclusion, the main factors of decreasing woods are 1) Demands of land parallel with the shift in industrial conditions, 2) Spatial conditions of each forest unit covering designation of specific areas, topographical condition, and so on.Thus in order to conserve woods, public support is necessary. In Group2 and 4, which have been urbanized earlier, public support to prevent conversion of woods into built-up area is needed. In groupl and 3, people own woods as property and are not willing to pay for the management. Public supports motivating woods management for the owners are needed.