Wetlands are disappearing at an alarming rate across the globe, an international environmental group reported Thursday, urging policymakers to do more.

Wetlands have disappeared by 35 percent between 1970 and 2015, at a rate of three times that of forests due to climate change and other "global megatrends" such as population increase and urbanization, according to the Ramsar Convention, the sole international treaty focused on wetlands.

Japan has been a contracting party since 1980 and has 50 Ramsar sites -- wetlands designated to be of international importance. Kushiro-shitsugen in the northernmost main island of Hokkaido became the first Ramsar site that year. The last four sites were designated in June 2015.

While the global outlook report did not look at individual nations, the Ramsar Convention has mentioned that Japan recognizes the importance of wetlands and is attentive to the conservation efforts.

Martha Rojas Urrego, secretary general of the conservation body, called for urgent action in the report, saying "the value of wetlands remains largely unrecognized by policy and decision-makers."

Wetlands act as a purifier of water, provide food, and "store more carbon than any other ecosystem," and in the context of climate change, increasing water demands and increased risks of floods and droughts, wetlands are "more critical than ever to achieve sustainable development."

The most recent estimate of global inland and coastal wetland area is in excess of 12.1 million kilometers square, an area almost as large as Greenland.

The largest areas of wetlands are in Asia, covering 32 percent of the global area. North American wetlands cover 27 percent, with Latin America and the Caribbean 16 percent. Wetland areas in Europe declined by 35 percent in the nearly half-century period and now covers only 13 percent, while Africa lost 42 percent of its wetlands. Latin America sustained the most loss by 59 percent.

In the same period, Human-made wetlands, largely rice paddy and reservoirs almost doubled now forming 12 percent of wetlands. However, the report warns that these increases have not compensated for natural wetland loss.

Many water-dependent species have been in decline. Of over 18,000 wetland-dependent species such as fish and water birds, a quarter are threatened with extinction.

The Ramsar Convention has been ratified by 90 percent of U.N. members, including major polluters such as the United States and China. Since coming into force in 1975, it has designated more than 2,300 sites of international importance.