An ancient basin of biodiversity
Upo Wetland is the largest natural inland wetland in South Korea, covering a total area of 2.3 square kilometers. The wetland complex consists of four main sections: Upo, Mokpo, Sajipo, and Jjokjibeol. Its formation dates back approximately 140 million years, created as soft ground in the area collapsed and filled with water from tributaries of the Nakdong River. This geological history makes it a rare example of a preserved primitive ecosystem, often called a "living natural museum".
The site’s international importance was formally recognized on March 2, 1998, when it was designated as a Ramsar Wetland of International Importance. This designation acknowledges its high biodiversity and role as a habitat. Upo supports around 1,500 species of flora and fauna. This includes 168 species of plants, 62 species of birds, and 28 species of fish. The wetland's hydrology is unique; it absorbs floodwaters, absorbing floodwaters from the Nakdong River during the summer monsoon season and maintaining a persistent water level even during dry periods.
The East Asian-Australasian flyway station
Upo Wetland is a stopover and wintering site for migratory birds along the East Asian-Australasian Flyway. More than 180 bird species have been observed here. Among the most significant visitors are hooded cranes (Grus monacha), which are classified as a vulnerable species by the International Union for Conservation of Nature (IUCN). These cranes breed in the remote wooded bogs of Siberia and northeastern China before migrating to their wintering grounds.
Other endangered or vulnerable species that rely on Upo include the white-naped crane (Antigone vipio), whooper swan (Cygnus cygnus), and the Eurasian spoonbill (Platalea leucorodia). The wetland provides feeding grounds. The diet for many of these birds consists of grains from surrounding agricultural fields, as well as plant stalks and roots found within the wetland itself. The site also has a significant population of falcated ducks (Anas falcata); it is estimated that almost 8 percent of the world's population of this species inhabits the area. A restoration project for the crested ibis (Nipponia nippon), once thought to be extinct in the area, was launched in 2008 and has seen successful breeding.