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 December 2015 had 169 contracting parties. Japan was the twenty-fourth party to accede, on 17 October 1980. Kushiro-shitsugen was the first of Japan's fifty-two Ramsar sites as of the thirteenth conference of the contracting parties (2018), with a total surface area of 1,547 square kilometres (597 sq mi).