Wetland is a place that is flooded by water either all of the time or part of the year. Wetlands are created either by rainfall or coastal seawater. All of the plants that live in a wetland have adapted to either a freshwater or saltwater environment. Often wetlands are no more than 3 feet (1 m) deep.
There are three broad wetland categories: freshwater wetlands, coastal saltwater wetlands, and inland saltwater wetlands. Freshwater wetlands are commonly on the margins of lakes or rivers, especially along river floodplains. Coastal saltwater wetlands occur where the land and the sea meet, often where freshwater flows into saltwater. Inland saltwater wetlands occur where evaporation concentrates salts in the surface layers of soil and seasonal rainfall mixes with the salts.
The main types of freshwater wetlands are fens, bogs, swamps, and marshes. Fens and bogs which together are called mires occur where there is constantly wet and peaty soil. They often receive groundwater as well as rainfall. Mires are usually found in temperate regions with high rainfall such as northern North America and northern Europe. Swamps are wetland forests, and marshes are wet grasslands. Two well-known wetlands that contain both swamps and marshes are the Okefenokee Swamp in southeast George and the Everglades in southern Florida.
Most saltwater wetlands occur where fresh and salt water mix, often where large rivers with wide floodplains approach the ocean creating large and wide deltas. Saltwater wetlands include brackish (slightly salty) and saltwater lagoons and salt marshes. Saltwater wetlands also occur inland, often in arid regions where seasonal rainfall and flooding creates temporary ponds, marshes, and other water bodies,
Wetlands are important ecosystems. They support a wide variety of plants and animals that have specially adapted to living in or near water. Freshwater wetland plants such as marsh marigolds have light, spongy stems and leaves that allow them to transport atmospheric oxygen to the roots. Saltwater wetland plants such as mangroves often have narrow leaves that help them conserve water that salt would draw out of them. Plants that grow at the edges of wetland such as reeds often have woody stems that allow them to survive short-term changes in water levels.
Many animals thrive in wetlands. Herons and egrets stalk their prey in shallow water; ducks filter-feed at the surface or dive for food, and waders hunt for prey just below the surface of wet mud. Many reptiles live in wetlands including frogs, snakes, freshwater turtles, crocodiles, and alligators. Many mammals live in wetlands including, rodents, beavers, muskrats, and capybaras. Larger wetland mammals include water buffalo, hippopotamuses, and jaguars.