Wetlands provide a remarkable range of ecosystem services, from filtering pollutants out of water to storing floodwaters, sequestering carbon, and supporting roughly 40% of all plant and animal species on Earth. Despite covering only about 6% of the planet’s land surface, their combined economic value has been estimated at $47.4 trillion per year, representing nearly half the value of all natural biomes. Yet since 1970, an estimated 411 million hectares of wetlands have been lost globally, a decline of about 22%, with losses continuing at roughly 0.52% per year.
Water Purification
Wetlands act as natural water treatment systems. As water moves slowly through wetland soils and vegetation, plants and microorganisms absorb excess nutrients, trap sediments, and break down contaminants. Freshwater wetlands remove a median of 37% of total nitrogen and 46% of total phosphorus from the water passing through them. These are the two nutrients most responsible for algal blooms and dead zones in lakes, rivers, and coastal waters. One caveat: wetlands restored on former farmland tend to be significantly less effective at phosphorus removal than other wetland types, likely because decades of fertilizer application have already saturated the soil.
Beyond nutrients, wetlands filter heavy metals, pesticides, and bacteria. The dense root systems of marsh grasses and aquatic plants physically slow water flow, giving sediments time to settle out. Microbes living in the oxygen-poor wetland soils then chemically transform many pollutants into less harmful forms. This is why constructed wetlands are increasingly used as low-cost wastewater treatment systems around the world.
Flood Control and Water Storage
A single acre of wetland can hold between 1 and 1.5 million gallons of water. Wetlands function like natural sponges during storms, absorbing runoff and releasing it slowly over days or weeks. This dramatically reduces flood peaks downstream. Floodplain wetlands along rivers are especially effective because they spread water across a wide area, lowering the volume and speed of flow in the main channel.
This storage capacity also works in reverse during dry periods. Wetlands that captured water during storms gradually release it into streams and shallow aquifers, helping maintain base flows when rain stops. Research in South Carolina found that both isolated wetlands (those not directly connected to rivers) and riverine wetlands actively recharge groundwater, with riverine wetlands averaging about 4.7 centimeters per day and isolated wetlands about 3.3 centimeters per day. Sandy soils beneath the wetlands drove much of this movement. The practical takeaway: wetlands don’t just reduce floods, they help keep wells and streams flowing during droughts.
Carbon Storage
Wetlands are among the most carbon-dense ecosystems on the planet. Waterlogged soils slow decomposition to a crawl, so dead plant material accumulates as peat or organic-rich sediment rather than releasing its carbon back into the atmosphere. Tidal wetlands, including salt marshes and mangrove forests, sequester about 8 tonnes of CO₂ per hectare per year. Seagrass meadows store roughly 1.6 tonnes per hectare per year. For context, tropical forests typically sequester between 3 and 6 tonnes per hectare annually, meaning coastal wetlands outperform them on a per-area basis.
This stored carbon, sometimes called “blue carbon” in coastal settings, can remain locked in wetland soils for centuries or millennia. The flip side is significant: when wetlands are drained or destroyed, that accumulated carbon oxidizes and enters the atmosphere as CO₂. Peatland drainage alone is a substantial source of global greenhouse gas emissions, which makes wetland conservation a surprisingly powerful climate strategy.
Coastal Protection
Mangrove forests, salt marshes, and coral-associated wetlands serve as buffers against storm surge and wave damage. Field measurements in mangrove forests show that wave height drops by about 62% within just 80 meters of forest, with roughly 76% of wave energy dissipated over that same distance. This means that even a relatively narrow band of mangroves can meaningfully shield shoreline communities and infrastructure from storm impacts.
Salt marshes provide similar protection through their dense, flexible vegetation, which absorbs wave energy without the rigid resistance that causes erosion. These natural barriers also adapt to rising sea levels in ways that concrete seawalls cannot. Healthy marshes build elevation over time as sediment and organic matter accumulate, effectively growing upward with the water. This adaptive capacity is one reason why coastal wetland restoration has become a mainstream strategy in shoreline management.
Biodiversity Habitat
Forty percent of all plant and animal species live or breed in wetlands. That figure is striking given how little land area wetlands occupy. They serve as nurseries for fish, nesting grounds for migratory birds, and critical habitat for amphibians, insects, and freshwater mussels. In the United States, roughly half of all federally listed threatened and endangered species depend on wetlands at some point in their life cycle.
Wetlands support this outsized biodiversity because they sit at the boundary between aquatic and terrestrial environments, creating a gradient of conditions. A single marsh may include open water, submerged vegetation, emergent reeds, saturated soil, and dry upland edges within a few hundred meters. Each zone supports different communities of organisms. Seasonal flooding adds another dimension, creating temporary habitats that many species have evolved to exploit. Vernal pools, for instance, provide breeding habitat for salamanders and frogs precisely because they dry up in summer, keeping fish predators out.
Food, Fiber, and Raw Materials
Wetlands directly supply products that billions of people depend on. Rice, the staple food for more than half the world’s population, grows in wetland paddies. Freshwater and coastal wetlands support fisheries that provide protein for communities across Africa, Asia, and Latin America. Beyond food, wetlands yield papyrus, reeds, and thatching grass used for construction and weaving. Peat has historically been harvested as fuel. Many wetland plants have traditional medicinal uses, and wetland timber from species like mangroves and cypress supports local economies.
These provisioning services are often most important to rural and low-income communities that depend directly on natural resources. In places like the Kano floodplain in Kenya, natural wetlands supply fiber, fish, and materials for mats alongside cultural services like spiritual practices and ecotourism. When wetlands are converted to single-use agriculture, the diversity of these benefits collapses even if crop yields rise in the short term.
Recreation and Cultural Value
Wetlands support hunting, fishing, birdwatching, kayaking, and nature photography, all of which generate significant economic activity. In the United States alone, wetland-dependent recreational activities contribute billions of dollars annually to local economies. Birdwatching tourism is especially tied to wetlands because marshes, estuaries, and mudflats concentrate migratory species in spectacular numbers during seasonal flyways.
Wetlands also hold deep cultural and spiritual significance for many Indigenous and local communities. They appear in creation stories, serve as gathering places, and provide materials for traditional crafts. These cultural ecosystem services are harder to quantify in dollar terms but are no less real to the people who depend on them.
Why Wetland Loss Matters
Coastal wetlands, despite making up only 15% of global wetland area, deliver an estimated 43% of the total economic value of wetland ecosystem services, roughly $20.4 trillion per year. They are also among the most threatened, facing pressure from coastal development, aquaculture, and sea-level rise. Inland wetlands face conversion to cropland and urban sprawl. The ongoing global loss rate of 0.52% per year may sound small, but it compounds. Since 1970, the world has lost an area of wetlands roughly the size of Ethiopia.
Each hectare of wetland lost means reduced flood storage, dirtier water, less carbon locked underground, and fewer species with viable habitat. Because these services interact (a wetland that filters water also stores carbon and supports fish), the loss of a single wetland degrades multiple services simultaneously. Restoration can recover some of these functions, but rebuilt wetlands rarely match the performance of intact natural ones, particularly for nutrient removal and carbon storage, where decades of soil development matter.