東京都水道水源林の形成過程－明治期に現れたいくつかの経営計画を中心として－

Abstract

近年，森林の公益的機能に対する一般の関心が高まりつつある中で，従来の木材生産中心の森林経営計画にかわって，森林の木材生産機能と公益的機能の両方に配慮した森林経営計画が求められている。このような多目的型の森林経営計画のあり方を展望する上で，90年余の経営蓄積を持ち，日本を代表する大都市水道局の所有・管理する森林である東京都水道水源林を対象として，研究を進めていく。筆者はこれまで，東京都水源林の経営計画の変遷について報告し，現在の経営計画は水源かん養機能高度発揮を目的とした水源林独自のものであることを明らかにした。しかし，水源林問題は河川をめぐる上下流の相互関係とも捉えられ，経営計画の変遷問題の解明にあたっても，この上下流の関係成立過程が極めて重要な意味を持つ。そこで，本研究では，水源林の経営前史における上下流の相互関係について明らかにすることを目的とした。 The Tokyo Metropolitan Forest for Water Supply Conservation has been managed since 1909 in order to conserve water resources. This paper is intended to clarify the process of formation of Tokyo City Forest; the forerunner of the Tokyo Metropolitan Forest in the Meiji era. Especially, this study gives attention to: 1) some forest management plans proposed at the beginning of the practical management of Tokyo City Forest, 2) conflicts of interests caused by different types of water usage: drinking, irrigation, water transportation, and so on. First, in the late Meiji era in the 1990s, some foresters had already pointed out one of the most important subjects concerned with the present forest management-the adjustment of timber production and non-timber production. Before the beginning of forest management by Tokyo city government, foresters submitted two different forest management plans to the Mayor of Tokyo, one in 1908 and the other in 1909. The most important difference between the former and the latter is concerned with the description of the relationship between timber production and water resource conservation. The former said that timber production was not inconsistent with water conservation. The latter said, to the contrary, that timber production was compatible with water conservation. The former recommended the restriction of local wood production and the purchase of forests in headwater areas. In this plan, the forests were to be harvested only under the wellorganized selection cutting system. But, the latter insisted that Tokyo city government was able to share the interests with landowners and local people through cooperative forest management, and that all the manageable forests were to be harvested under the plantation and clear cutting system. Second, the formation of Tokyo City Forest was one of the steps to settle the conflicts between Tamagawa headwater areas and Tokyo city. The forest management for water supply conservation by Tokyo city government had begun with the muddy water problem and the shortage of water caused by the deforestation in headwater areas. Villagers in headwater areas often conflicted with citizens in Tokyo concerning water use and land use of the Tamagawa river basin. Since the citizens of Tokyo used the river mainly for drinking, they have been interested in the safety of the water supply in terms of both quantity and quality. This interest often disagreed with economic activities in headwater areas, such as timber logging, water transportation, and clearing forest for raising silkworms.