A wetland is a type of ecosystem in which the land is covered in or saturated with water. Wetlands can be covered in water seasonally or permanently, and feature hydric soil, which is soil that is saturated in water and creates anerobic conditions, and hydrophytes, which are aquatic plants that have adapted to growing in water or saturated soil. In most cases, wetlands are caused by the seeping of water from springs or aquifers to the surface. Flooding from lakes, rivers, or other bodies of water can also create wetlands. The types of plants that grow in wetlands are generally adapted to water saturation and lack of oxygen, but vary depending on degree of saturation. Wetlands exist in various climates and in all continents, except Antarctica.
Types of Wetlands
Wetlands vary in size, ranging from small prarie potholes to vast salt marshes, and can exist both inland and along the coast. Some wetlands are covered in trees, while others are full of grass and spongy moss. There are three main types of wetlands, which are marshes, bogs, and swamps, as well as sub-types such as peatlands, muskegs, potholes, and mires.
A swamp is a type of wetland that is permanently saturated by water and dominated by undergrowth and trees. There are two types of swamps: freshwater swamps and saltwater swamps. Freshwater swamps are formed by rivers, streams, or freshwater lakes, and usually occur on flat land around bodies of water where surface runoff is slow and the water table is high. Rainwater and seasonal flooding cause fluctuations in the degree of water saturation. These types of swamps are common near the Equator, where temperatures and humidity remain high throughout the year. For example, the Congolian swamp forests along the banks of the Congo River are some of the most extensive freshwater swamps in the world. Saltwater swamps exist along the coastlines of bodies of water that have a high salinity, such as oceans and seas, and are formed when saltwater covers flats of sand and mud during the high tide. When seawater and freshwater converge, a swamp with brackish water is formed. Mangroves are an indication of a saltwater swamp, but mostly thrive in brackish waters.
A marsh is a type of wetland that includes herbacious plant species, such as grasses, rushes and reeds, rather than woody plants. Marshes tend to form near the transition between terrestrial and aquatic ecosystems, such as near the edge of rivers, lakes or streams, and are exposed to a flow of water that either drains or floods the area. Freshwater marshes can exist hundreds of miles from the coast, such as the vast freshwater marshes in the prairie pothole regions across Central Canada and the Midwestern United States. Saltwater marshes develop close to the ocean or sea, are mostly affected by tides, and form some of the richest ecosystems in the world. The tides of the Pacific Oocean and Indian Ocean have formed vast saltwater marshes in northern Australia, which provide a habitat for shellfish, fungi, algae, reptiles, fish, birds, and amphibians.
While marshes and swamps form in warm climates, bogs are common in cold regions of the Arctic, North America, Asia, and Europe. However, bogs can also exist at high altitudes in warm areas. Like other types of wetlands, bogs form in regions where the water table is high, and often originate from a glacial depression, known as a kettle lake, which is much deeper than a prairie pothole. Debris gradually fills the lake, making it shallower and enabling the growth of plants. Bogs are referred to as muskegs in Canada, and as fens or moors in Europe.
Wetlands act as reservoirs and giant sponges that absorb water during heavy rains and prevent flooding. They also protect coastal regions from storms that destroy fragile beaches, and provide a habitat for various forms of plant and animal life. Wetlands are also popular destinations for recreational activities such as hiking, hunting, bird-watching, and canoeing.