The Ramsar Convention on Wetlands of International Importance especially as Waterfowl Habitat is an international treaty for the conservation and sustainable use of wetlands. Adopted in 1971, it entered into force in 1975 and as of February 2026 had 172 contracting parties. Japan was the 24th party to accede, on 17 October 1980. Kushiro-shitsugen was the first of Japan's 54 Ramsar sites as of February 2026, with a total surface area of 1,661 square kilometres (641 sq mi).