Environment

Environment
A Time to Unwind the Marshlands - Kushiro Marsh Restoration Trajectory (February 2007 - March 2011 Environment)

Until the 1970s, Kushiro Marsh was progressively converted to a straightened river channel (a new waterway) for the purpose of flood protection and land use expansion, resulting in the lowering of water levels on flood plains and the aridification of the marshland. According to national data, shortcuts were implemented in the Kushiro River main river and branch rivers from the 1920s to the 1980s, and while the old river channels remain as river trace lakes, the ecosystem and landscape have been greatly altered.

The tide of nature conservation and restoration turned in the 1990s, with the designation of Kushiro Marsh National Park in 1987 and the 1993 Ramsar Convention Conference of the Contracting Parties (COP5) held in Kushiro City, which widely shared the international significance of marshland conservation in Japan and abroad. In 1997, the River Law was amended to clearly state the need for "improvement and conservation of the river environment," and in 1999, the "Study Committee on the Conservation of the River Environment of Kushiro Marshland" was established, steering the policy toward the restoration of nature in the entire river basin.

The key to the technical aspects of the project is the restoration of the old river (meandering restoration). The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has announced a policy of restoring the straightening section to its original meandering to the extent possible, and has designated the Kayinuma area of the main river (approximately 2 km) as a test site. In addition, arrangements have been made to restore the meandering shape of the Hororo, Yukuri, Numaoro, Osobetsu, and other tributary rivers within a period of about five years. The aim was to optimize the frequency of flooding, restore vegetation on the floodplain, control downstream runoff of nutrients and sediment, and restore habitat for fish and aquatic insects and the wetland landscape.

The implementation scheme is also unique. Under the Kushiro Marsh Nature Restoration Council, the national government (Kushiro Development and Construction Department, Hokkaido Development Bureau), local governments, research institutes, and residents shared the roles and responsibilities. In addition to engineering, Kushiro's approach is to accumulate microtopography-scale treatments, such as partial lowering of levees, blockage of old drainage channels, and creation of wand and ford, after repeated preliminary forecasts of ecological, landscape, and agricultural land impacts.

Citizen participation has also been a major pillar of the project since that time. Kushiro International Wetland Center (KIWC) repeatedly surveyed aquatic organisms, vegetation, sedimentary soil, and landscape in and around the meandering restoration section with citizens to visualize the impact of straightening and changes after restoration. Linking with school studies and observation sessions, KIWC will connect conservation with local pride and learning.

The background of the times is a sense of crisis over global wetland loss, a policy shift in Japan toward nature restoration after overcoming pollution, and a change in values in tourism from "seeing" to "learning/being involved. The symbolic change is the shift from "seeing" to "learning" and "being involved. Symbolic of this change is the full-scale meandering restoration project that was carried out from February 2007 to March 2011. The effectiveness of the project was verified by setting four goals: ecology, flood control, water quality, and landscape. Results were reported in terms of restoration of floodplain vegetation due to increased flooding frequency in the restored river channel, improvement of aquatic habitat, and reduction of downstream wetland load due to nutrient and sediment trapping.

In short, Kushiro's restoration was an effort to untangle the straight line and return time to the marsh. The direction was set by institutions (national parks, Ramsar, and revision of the River Law), water and soil cycles were restored through meandering restoration connecting engineering and ecology, and citizens' monitoring and learning provided constant support. In this way, the wetlands were reevaluated not only as a landscape asset, but also as an infrastructure that unites flood control, water quality, and biodiversity.