中海・宍道湖の干拓・淡水化事業は, 1988年に地元を中心とする反対運動によって, 淡水化について事実上の中止に追い込まれた。干拓事業については1990年代半ばになって再び事業を進めるか否かが問い直されている。本稿では前者の淡水化事業が凍結されるまでの反対運動に注目し, その地域性及びその意味を明らかにする。反対運動は, 宍道湖でシジミ漁を営む漁民や生活環境・観光資源を重視する松江市民らを中心として, 広範に展開された。この一連の反対運動は, 関係する地域で一様な展開をみせたわけではなく, その発生や展開過程において顕著な地域差をみせた。それは, 鳥取県と島根県という行政領域の違い, 中海と宍道湖という直接の関心事となる対象の違い, 都市部と農村部という社会経済環境の違いという3つの視点からとらえることができる。環境保全運動は, 対象が, その存在する地域と不可分なことや, 運動の担い手がその地域の住民であること等のために, 地域性を反映したものとなる。今回の例では, 松江中心で運動が進んだために, 「宍道湖を守ろう」という性格の強い運動となった。運動を成功させるためにも, また, 当事者間の主張や利害関係を調整し, 問題を解決するためにも, 表面的な争点にとどまらず, 地域構造上の問題点に踏み込んだ環境問題の理解が求められる。, The study purports clarification of regional characteristic of the environmental movements to oppose the Project of Land Redamation in Lake Nakaumi, which also includes a sub-project to alter the two brackish lakes, Lake Nakaumi and Lake Shinji, into freshwater lakes. This project has been suspended by the pressure from these movements. Precisely speaking, the sub-project to alter the lakes into freshwater lakes was actually cancelled in 1988, and the main project to reclaim land from Lake Nakaumi is still a matter of controversy between the local goverments and the local residents. The subject of this paper is to examine the movements which continued to the time when the former project was cancelled. The opponents against the project consisted of people who lived around the lakes, especialy fishermen gathering shijimi clams and citizen of Matsue city. These movements, which were expanded rapidly and widely during 1980's, made remarkable regional differences in the development process. It is possible to see these movements from three points of regional dichotomy. The first is a relation between Tottori and Shimane prefecture, which explains the characteristic of the organization and spatial extent of the movements. The second is that between Lake Nakaumi and Lake Shinji, which explains the characteristic of the concern of residents and strategy of the movements. The third is that between the urban area and the rural area, which explains the charactor of the leaders and the supporters. The movements might ultimately inquire how to evaluate and make use of these two lakes as the regional resources. In this case, many people hoped Lake Shinji to be preserved as a brackish lake which would provide shijimi clams and many kind of fish, and which would be an essential element of the landscape in an old city, Matsue. So the movements laid a stress on the preservation of Lake Shinji, though the projects would have worse influences upon Lake Nakaumi. An environmental preservation movement reflects the figure of the region facing environmental plobems. To clarify the regionnal characteristics in the environmental preservation movements is important not only for the study of social movement theory but also for the study of regional development planning and environmental management.