Abstract
In 2001 the Hokkaido Regional Development Bureau (HRDB) published the "Proposal for Conservation of the River Environment in Kushiro Mire" (a Ramsar site). One of the 12 themes of the report was that of controlling the vegetation of the mire, specifically, the increase in black alder distribution and decrease in reed and sedge colonies, which are river environment indicators. HRDB carried out a large-scale (over 200ha) field experiment to raise the groundwater level by closing the Setsuri sluice in the Yasuhara River area from September 2000 to May 2003. During this time, the alder forest occupied only a small part of the flooding area, and changed little. However, our surveys from 2004 found that much of the original sedge and reed vegetation was replaced by a new community of Bidens and Persicaria species, typical of a disturbed riverside environment. This type of vegetation had never been recorded before in the Kushiro Mire. It is important to learn from this case so that future attempts at restoration can be more successful. Such projects should clearly allocate responsibilities and be based on sufficient preliminary surveys and predictive models.
