Marsh
A marsh is — according to ecological definitions — a wetland that is dominated by herbaceous rather than woody plant species.[1] More in general, the word can be used for any low-lying and seasonally waterlogged terrain. In Europe and in agricultural literature low-lying meadows that require draining and embanked polderlands are also referred to as marshes or marshland.
For other uses, see Marsh (disambiguation).
Marshes can often be found at the edges of lakes and streams, where they form a transition between the aquatic and terrestrial ecosystems. They are often dominated by grasses, rushes or reeds.[2] If woody plants are present they tend to be low-growing shrubs, and the marsh is sometimes called a carr. This form of vegetation is what differentiates marshes from other types of wetland such as swamps, which are dominated by trees, and mires, which are wetlands that have accumulated deposits of acidic peat.[3]
Marshes provide habitats for many kinds of invertebrates, fish, amphibians, waterfowl and aquatic mammals.[4] This biological productivity means that marshes contain 0.1% of global sequestered terrestrial carbon.[5] Moreover, they have an outsized influence on climate resilience of coastal areas and waterways, absorbing high tides and other water changes due to extreme weather.[5] Though some marshes are expected to migrate upland, most natural marshlands will be threatened by sea level rise and associated erosion.[5]
Values and ecosystem services[edit]
Marshes provide habitats for many kinds of invertebrates, fish, amphibians, waterfowl and aquatic mammals.[4] Marshes have extremely high levels of biological production, some of the highest in the world, and therefore are important in supporting fisheries.[1]
Marshes also improve water quality by acting as a sink to filter pollutants and sediment from the water that flows through them. Marshes partake in water purification by providing nutrient and pollution consumption.[6] Marshes (and other wetlands) are able to absorb water during periods of heavy rainfall and slowly release it into waterways and therefore reduce the magnitude of flooding.[7] Marshes also provide the services of tourism, recreation, education, and research.[6]
Restoration[edit]
Some areas of the world have already lost 90% of their wetlands, including marshes. They have been drained to create agricultural land or filled to accommodate urban sprawl. Restoration is the process of returning marshes to the landscape to replace those lost in the past.[1] Restoration can be done on a large scale, such as by allowing rivers to flood naturally in the spring, or on a small scale by returning wetlands to urban landscapes.