著者

大嶋 和雄 斎藤 文紀

出版者

地学団体研究会

雑誌

地球科学 (ISSN:03666611)

巻号頁・発行日

vol.47, no.3, pp.213-231, 1993

---

Tokyo Bay is badly polluted, but would be in much worse shape were in not for sewage treatment and regulation. Such management techniques for water quality have rid the bay of toxic mercury sludge, and have made the average water quality of the bay head up to Class C rating, which indicates no unpleasant effects on everyday life. The bay still yields fishery products; a 30,000-ton catch in 1990. However, its yield is less than only a third of the maximum of the past fisheries yield. There is a limit, however, to technology. To bring the water quality rating of the entire bay up to Class B, suitable for fishing, would require that treated sewage dumped into the bay be able to support marine life. The construction of sewage treatment plants to perform such a feat would be prohibitively expensive, and the cost of the treatment would be a continuing liability, not a one-time fix. In other words, though technology can keep death at bay, it alone cannot restore Tokyo's coastal area to health. A Tokyo-Bay restoration project must harness the area's natural ability to recover from environmental damage. That recovery is accomplished through three mechanisms; sea-water exchange, sedimentation, and biological production. The coast is the interface between land and sea, where its ecosystem has developed over thousand of years. Technology works to fight pollution, but only to a point. Coastal restoration projects must be designed to work with the powerfull cleaning system of the bay itself if they are to assist truly sustainable development.