Marshes, swamps, bogs, mangroves and other wetlands make our lives better in unexpected ways. Wetlands are the first line of defense against flooding and are some of the most biodiverse ecosystems on Earth. They are able to hold and filter fresh water, and over the long term, can sometimes store more carbon per hectare than tropical forests.
Developed by the World Wildlife Fund and the University of Kassel in Germany, the Global Lakes and Wetlands Database (GLWD) hosted on Resource Watch shows the location and type of 10 million square kilometers of wetlands, which cover about 7 percent of the earth’s surface. The map also includes large lakes (bigger than 50 square kilometers) and man-made reservoirs, which cover about 2 percent of the earth’s surface.
There are nine wetland types in the dataset, but areas that aren’t completely covered with wetlands are categorized as having partial wetland coverage without specifying wetland type.
About 30 percent of the world’s wetlands are located in North America. Some of them developed after previous glaciation created lakes. Asia and North America combined contain over 60 percent of the world’s wetland area.
Since 1900, over half of the world’s wetland area has disappeared, according to the World Wildlife Fund. The global distribution of wetlands data was published in 2004, and may not reflect current wetland area. Mapping these critical ecosystems that store freshwater and carbon is essential to understanding how choices we make about infrastructure and development will affect the future.
Wetland conservation is important for avoiding carbon emissions as well as protecting coastlines from flooding. A 2017 analysis from World Resources Institute (WRI) found that protecting carbon-rich wetlands such as peatlands is one of the most effective ways to avoid carbon emissions. Peatlands accumulate organic matter over many years and have the most carbon-rich soils in the world. The study estimates that each hectare of tropical peat drained for plantation development emits an average of 55 metric tons of carbon dioxide every year, equivalent to burning about 6,000 gallons of gasoline.
Wetlands around the world are under threat from human settlement and rising seas. Many coastal wetlands depend on fresh water, but rising sea levels are inundating these habitats. Some of them cannot thrive in saltier water.
The world’s largest mangrove forest, which spans from the eastern edge of India to southwestern Bangladesh, is being threatened by these pressures. More than 13 million people call the swampy Sundarbans home. The map below shows population pushing right up against the border of the mangroves . (See data on the world’s mangrove forests from the United States Geological Survey.)
Overlay likely urban expansion and sea level rise with the wetland map to see which areas may have an uncertain future.