Wetlands cover roughly 1.4 billion hectares of the Earth’s land surface, spanning every continent except Antarctica. That’s about 13.4% of the world’s total land area, and they show up in far more places than most people expect: from Arctic tundra to tropical river basins, coastal shorelines to mountain peaks above 5,000 meters.
Distribution by Continent
Asia holds the largest share of the world’s wetlands by a wide margin, containing 43.8% of the global total. Much of this concentration sits in the vast lowlands of Siberia and the river floodplains of South and Southeast Asia. North and Central America follow with 26.7% of global wetland area, driven largely by the enormous peatlands and bogs stretching across northern Canada.
What’s striking is the density of coverage in these two regions. Nearly one-fifth of North and Central America’s total land area (19.9%) qualifies as wetland, and Asia is close behind at 18.7%. By contrast, Africa and Oceania have the lowest ratios at just 5.3% and 6.5% of their land area, respectively. South America and Europe fall somewhere in between, with South America’s share dominated by the Amazon basin and Europe’s concentrated in Scandinavia and Russia’s western reaches.
The World’s Five Largest Wetland Systems
A handful of massive systems account for an outsized share of the world’s wetland area. The largest is the West Siberian Lowland in Russia, stretching across roughly 2.7 million square kilometers of peatland, bogs, and marshes. It’s one of the biggest continuous wetland landscapes on the planet, storing enormous quantities of carbon in its waterlogged soils.
The Amazon River Basin in South America ranks second. Its seasonally flooded forests and permanent swamps form a wetland network that pulses with the annual flood cycle, with water levels rising and falling by several meters each year. Third is Canada’s Hudson Bay Lowland, a vast expanse of peat bogs and fens ringing the southern shore of Hudson Bay. The Mackenzie River Basin, also in Canada, ranks fifth.
Sandwiched between those two Canadian systems at number four is the Congo River Basin in Central Africa. Despite Africa’s relatively low overall wetland coverage, the Congo’s swamp forests represent one of the most significant tropical wetland systems on Earth, second only to the Amazon among tropical river basins.
Coastal Wetlands vs. Inland Wetlands
Wetlands split broadly into two categories based on where they form. Coastal wetlands, including tidal marshes, mangrove forests, and estuaries, develop along protected shorelines where rivers meet the ocean. Tidal marshes are found along coastlines in middle and high latitudes worldwide, with particularly extensive systems along the eastern coast of North America from Maine to Florida and around the Gulf of Mexico into Texas. Mangrove forests occupy tropical and subtropical coasts, thriving in places like Southeast Asia, West Africa, Central America, and northern Australia.
Inland wetlands are far more widespread. Non-tidal marshes form along streams, in poorly drained depressions, and in the shallow margins of lakes, ponds, and rivers. They appear wherever water collects and persists long enough to support water-adapted plants. Swamps, bogs, and fens are all inland wetland types found in river floodplains, groundwater seeps, and areas with high rainfall or slow drainage. The boreal forests of Canada, Scandinavia, and Russia are particularly rich in inland peatlands, where cold temperatures slow decomposition and allow thick layers of organic material to accumulate over thousands of years.
Wetlands in Unexpected Places
Wetlands aren’t limited to lush, rainy environments. In arid and semi-arid regions, ephemeral wetlands form along intermittent streams that flow only during and shortly after rainfall. In the American Southwest, 79% to 94% of streams in states like Arizona, Nevada, New Mexico, and Utah are intermittent or ephemeral. These temporary waterways create brief but ecologically important wetland conditions in landscapes where evaporation far exceeds rainfall. Desert oases in North Africa and the Middle East function similarly, sustaining wetland ecosystems fed by underground springs.
High-altitude wetlands are another surprising category. The Hindu Kush Himalayan region, stretching over 3,500 kilometers across South Asia, contains lakes, marshes, and alpine bogs at elevations well above 4,000 meters. These mountain wetlands act as freshwater reservoirs feeding major river systems including the Ganges, Indus, Yangtze, and Mekong, which collectively supply water to billions of people. The Gokyo wetlands near Mount Everest in Nepal sit above 4,700 meters, making them among the highest wetland systems in the world. Similar high-altitude wetlands exist in the Andes, the Ethiopian Highlands, and the Tibetan Plateau.
How Much Has Been Lost
The global picture has shifted dramatically in recent decades. Since 1970, an estimated 411 million hectares of wetlands, roughly 22% of the global total, have been lost. The decline continues at an annual rate of about 0.52%, driven primarily by agricultural conversion, urban development, and water diversion projects. Drainage for farming has historically been the single biggest cause, particularly in temperate regions of North America, Europe, and East Asia where fertile wetland soils attracted intensive agriculture.
The remaining 1.4 billion hectares deliver ecosystem services valued at up to $39 trillion annually, more than any other ecosystem type. Those services include flood control, water filtration, carbon storage, and habitat for fish and wildlife. International efforts to protect what remains have designated over 2,500 Ramsar Sites of International Importance across 172 countries, covering about 2.5 million square kilometers. The United Kingdom holds the most individual sites at 176, followed by Mexico with 144, though site count doesn’t necessarily reflect total protected area since sites vary enormously in size. Together, these protected wetlands represent roughly 14% to 17% of the world’s remaining wetland area.