February 15, 2004


Wetland Preservation Protects Ecosystems and Cleanses Our Oceans: Yatsu-higata Wetlands: Sanbanse

* This article is under copyright protection.

Manabu Akaike
Universal Design Intelligence Inc.

Wetlands Are the Best Home for Marine Life

The dramatic protest at sea mounted in January 2001 by the commercial fishermen of the four prefectures comprising the Ariake Sea coastal region against the Isahaya Bay reclamation project rallied 1,500 fishing vessels with banners reading "Give Us Back the Treasures of the Sea!" in a graphic and powerful expression of the criticality of the situation and the anger of the fishermen. It had been four years since the Isahaya Bay sea wall was closed. The Ariake Sea had been the wetland habitat for some indigenous species including the mutsugoro mudskipper fish, but was now moving inexorably toward becoming a dead sea where no species could live, as represented by the extinction of the asari clam and failure of the nori seaweed harvest.

Most wetlands are formed by the build-up of silt and organic matter brought over many years down the rivers that empty into the sea. Alternately underwater and exposed to the atmosphere by the ebb and flow of the tides, wetlands receive a supply of oxygen every time they are exposed to the air. Since seaweed and types of bacteria thrive in this environment, wetlands form a wonderful home for plankton, crustaceans, marine worms and clams. Wetlands are also a rich source of food for fish when submerged and migratory birds when exposed.

The existence of this type of ecosystem leads in the end to a cleaner ocean. The destruction of wetlands means the extinction of living species and the loss of ecosystems, and the ultimate acceleration of the contamination of our ocean waters.

An international conference was convened at Ramsar in Iran in 1971 with the goal of conserving wetlands of international importance, especially as waterfowl habitats. The Convention on Wetlands signed then, known generally as the Ramsar Convention, called for the protection of many coastal areas. Our nation has registered a number of marsh and lake areas from the largest wetland in the nation of Kushiro Marsh to Kiritappu Marsh and Lake Biwa to aid in planning their conservation.

One of these sites is the Yatsu-higata Wetland, which was registered in 1993, located in the city of Narashino in Chiba Prefecture. As reclamation of land from Tokyo Bay advances, this wetland has become isolated about 200 kilometers inland from the bay, connected to Tokyo Bay by two narrow river channels. This tiny patch of wetland is less than four kilometers in circumference, existing today like a pool surrounded by concrete on all four sides. In 1994, the Yatsu-higata Nature Observation Center was set up, and the site serves as a prime location for observing wild birds and making environmental studies.

On the other hand, we have the Sanbanse tidal flats, a huge expanse of wetland covering 1,200 hectares reaching far offshore and stretching from Ichikawa City to Funabashi City. Here over the last thirty years a drama has been played out in the struggle between reclamation project planners and the citizen groups that oppose them.

The Thirty-Year War Against Wetland Reclamation

The Yatsu-higata wetlands and the Sanbanse tidal flats, both on the Chiba side of Tokyo Bay. Already more than 100 species of wild bird have returned to Yatsu-higata, whose continued existence as a wetland has been assured by the conservation policies now in place. But this wetland, which years ago sat right on Tokyo Bay bordering on the Sanbanse tidal flats, is now cut off from the water and isolated inland. Standing in Yatsu-higata, one would never be able to step onto a sandy shore, or even see a clear view of the horizon. The reflections of high-rise condos and buildings mar the water's surface. This wetland seems as if it had been carved out of the surrounding cityscape.

In contrast, the Sanbanse tidal flats located at the northernmost end of Tokyo Bay remain substantially the way they were in ancient times, a fertile fishing ground where one can enjoy clamming at low tide. This is the northernmost habitat for the treasured mudskipper fish. More than 170 wild bird species have been identified here, and the site is an important stop-off point for many migratory birds. Some studies show that the wild birds that live and multiply in the Yatsu-higata wetlands also come and go over the Sanbanse tidal flats, and many say that Yatsu-higata can only exist because of Sanbanse. In the cyclical movement of the tides' ebb and flow at Sanbanse thrive many benthic organisms, so-called bottom feeders, like marine worms, clams and crustaceans, that enhance the natural purifying action of the marine shallows and contribute greatly to cleaner water in Tokyo Bay.

But a major reclamation project proposed for Sanbanse has been the object of repeated protests by citizens' groups over the last thirty years. Among various actions against the reclamation including petitions by groups like the Sanbanse Preservation Council, protesters were successful in having the period of time allotted for the supplementary study of the ecosystem extended, and the reclamation project was eventually revised, but has not been returned to a clean slate.

In January 2001, Minister of Environment Yoriko Kawaguchi inspected Sanbanse and declared her intention that "the project should be revisited from every angle including curtailing the area of land to be reclaimed." There is no need to look at the Ariake Sea there are many past examples of how easy it is to lose nature and how difficult it is to regain it. Reflecting on issues like this led to the shift from nature conservation to nature restoration movements, and to the rethinking of a major public works project.

The drainage reclamation project at Shiwha Lake in Korea was begun at the same time as the one in Isahaya Bay. A regulating reservoir was constructed using embankment sea walls to cut off the tidal flats from the ocean, but the drainage project failed when toxic pollutants entered the lake. It was decided to reopen the sea walls in February 2001.

What is needed today is a clear-headed appraisal of exactly what are the mid- and long-term benefits that can be brought to an area both by ecosystem conservation and urban infrastructure projects such as roads and waste disposal facilities.

JAPAN CLOSE-UP, July 2002, published by PHP

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