ミニ特集: 健全な河川とは？ MINI-FEATURE: WHAT IS RIVER HEALTH
OPINION OPINION

健全な生態系とは何か？その評価と復元

島谷幸宏

Yukihiro SHIMATANI: What is a healthy ecosystem? For its evaluation and restoration Ecol. Civil. Eng. 4(1), 19-25, 2001.

Public Works Research Institute, Ibaraki, 1-6 Minamihara, Tsukuba 305-8516, Japan

Abstract:In this report, I discussed what a healthy ecosystem means from my own experience. I think that ecosystem health is determined by the conditions under which “the organisms that should be found in that ecosystem can properly survive”. Then, what sorts of species, species assemblages, local populations and individuals are those “that should be found there” ? Does “properly survive” mean that the standing crop is bigger than certain size ? Can they complete the life cycle ? Don't they become extinct in the course of natural fluctuations in abundance ? In order to answer those questions, we should consider with historical changes of the natural environment and interactions between people and water environments. It is clear that evaluation and restoration of “healthy ecosystem” should be based on mutual relationships between nature and human beings.

Key words: healthy ecosystem, Tama River, nature-oriented river works, Shinji Lake, Kita River

2001年5月10日受付，2001年6月11日受理
e-mail: y-shima@pwri.go.jp