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A marsh is a
wetland A wetland is a distinct ecosystem An ecosystem is a community (ecology), community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These Biotic component, biotic and abiotic c ...
that is dominated by
herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground, including many perennials, and nearly all annuals and biennial Biennial means (an event) lasting for two years or occurring every two years. The related te ...
rather than
woody plant A woody plant is a plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, ...
species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found at the edges of lakes and streams, where they form a transition between the aquatic and terrestrial
ecosystems An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system A system is a group of Interaction, interacting or interrelated elements that act according to a set ...
. They are often dominated by grasses, rushes or reeds. If woody plants are present they tend to be low-growing shrubs, and then sometimes called carrs. This form of vegetation is what differentiates marshes from other types of wetland such as
swamps A swamp is a forested wetland A wetland is a distinct ecosystem An ecosystem is a community (ecology), community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These Biotic ...
, which are dominated by
tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only wood plants with se ...

tree
s, and
mire , one of the largest fens in Estonia. A mire, peatland or quagmire is a wetland type, dominated by living peat-forming plants. Mires arise because of incomplete decomposition of organic matter, usually litter from vegetation, due to water-logg ...
s, which are wetlands that have accumulated deposits of acidic
peat Peat (), sometimes known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem An ecosystem is a c ...
. Marshes provide
habitat In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Topics of interest include ...
s for many kinds of invertebrates,
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. They form a sister group to the tunicates, together forming the Chordate#Taxonomy, olfactores. Included in this def ...
, amphibians, waterfowl and aquatic mammals. This biological productivity means that marshes contain 0.1% of global sequestered terrestrial carbon. 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. Though some marshes are expected to migrate upland, most natural marshlands will be threatened by
sea level rise Tide gauge measurements show that global sea level rise began around the start of the 20th century. Between 1900 and 2016, the globally averaged sea level rose by . More precise data gathered from satellite radar measurements reveal an acceler ...
and .


Basic information

Marshes provide a habitat for many species of plants, animals, and insects that have adapted to living in flooded conditions. The plants must be able to survive in wet mud with low oxygen levels. Many of these plants, therefore, have aerenchyma, channels within the stem that allow air to move from the leaves into the rooting zone. Marsh plants also tend to have
rhizome Lotus rhizome peeled and sliced In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds ...
s for underground storage and reproduction. Common examples include cattails, sedges, Cyperus papyrus, papyrus and Cladium, sawgrass. Aquatic animals, from fish to salamanders, are generally able to live with a low amount of oxygen in the water. Some can obtain oxygen from the air instead, while others can live indefinitely in conditions of low oxygen. The pH in marshes tends to be neutral to alkaline, as opposed to bogs, where peat accumulates under more acid conditions.


Values and ecosystem services

Marshes provide
habitat In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Topics of interest include ...
s for many kinds of invertebrates,
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. They form a sister group to the tunicates, together forming the Chordate#Taxonomy, olfactores. Included in this def ...
, amphibians, waterfowl and aquatic mammals. Marshes have extremely high levels of biological production, some of the highest in the world, and therefore are important in supporting fisheries. 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. 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. Marshes also provide the services of tourism, recreation, education, and research.


Types of marshes

Marshes differ depending mainly on their location and salinity. Both of these factors greatly influence the range and scope of animal and plant life that can survive and reproduce in these environments. The three main types of marsh are salt marshes, freshwater tidal marshes, and freshwater marshes. These three can be found worldwide and each contains a different set of organisms.


Salt marshes

Saltwater marshes are found around the world in mid to high latitudes, wherever there are sections of protected coastline. They are located close enough to the shoreline that the motion of the tides affects them, and, sporadically, they are covered with water. They flourish where the rate of sediment buildup is greater than the rate at which the land level is sinking. Salt marshes are dominated by specially adapted rooted vegetation, primarily salt-tolerant grasses.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Salt marshes are most commonly found in lagoons, estuaries, and on the sheltered side of shingle or Sandspit (landform), sandspit. The currents there carry the fine particles around to the quiet side of the spit and sediment begins to build up. These locations allow the marshes to absorb the excess nutrients from the water running through them before they reach the oceans and estuaries. These marshes are slowly declining. Coastal development and urban sprawl has caused significant loss of these essential habitats.


Freshwater tidal marshes

Although considered a freshwater marsh, this form of marsh is affected by the ocean tides. However, without the stresses of salinity at work in its saltwater counterpart, the diversity of the plants and animals that live in and use freshwater tidal marshes is much higher than in salt marshes. The most serious threats to this form of marsh are the increasing size and pollution of the cities surrounding them.


Freshwater marshes

Ranging greatly in both size and geographic location, freshwater marshes make up the most common form of wetland in North America. They are also the most diverse of the three types of marsh. Some examples of freshwater marsh types in North America are:


Wet meadows

Wet meadows occur in areas such as shallow lake basins, low-lying depressions, and the land between shallow marshes and upland areas. They also occur on the edges of large lakes and rivers. Wet meadows often have very high plant diversity and high densities of buried seeds. They are regularly flooded but are often dry in the summer.


Vernal pools

Vernal pools are a type of marsh found only seasonally in shallow depressions in the land. They can be covered in shallow water, but in the summer and fall, they can be completely dry. In western North America, vernal pools tend to form in open grasslands, whereas in the east they often occur in forested landscapes. Further south, vernal pools form in pine savannas and flatwoods. Many amphibian species depend upon vernal pools for spring breeding; these ponds provide habitat free from fish which eat the eggs and young of amphibians. An example is the endangered gopher frog (''Rana sevosa''). Similar temporary ponds occur in other world ecosystems, where they may have local names. However, the term vernal pool can be applied to all such temporary pool ecosystems.


Playa lakes

Playa lakes are a form of shallow freshwater marsh that occurs in the southern high plains of the United States. Like vernal pools, they are only present at certain times of the year and generally have a circular shape. As the playa dries during the summer, conspicuous plant zonation develops along the shoreline.


Prairie potholes

Prairie potholes are found in the northern parts of North America as the Prairie Pothole Region. These landscapes were once covered by glaciers, and as a result shallow depressions were formed in great numbers. These depressions fill with water in the spring. They provide important breeding habitats for many species of waterfowl. Some pools only occur seasonally while others retain enough water to be present all year.


Riverine wetlands

Many kinds of marsh occur along the fringes of large rivers. The different types are produced by factors such as water level, nutrients, ice scour, and waves.Day, R., P.A. Keddy, J. McNeill and T. Carleton. 1988. Fertility and disturbance gradients: a summary model for riverine marsh vegetation. Ecology 69: 1044-1054


Embanked marshlands

Large tracts of tidal marsh have been embanked and artificially drained. They are usually known by the Dutch name of polders. In Northern Germany and Scandinavia they are called '':de:Marschland, Marschland'', ''Marsch'' or ''marsk'', in France ''marais maritime''. In the Netherlands and Belgium they are designated as marine clay districts. In East-Anglia the embanked marshes are also known as The Fens, Fens.


Restoration

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. 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.


See also

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References


External links


Marshes of the Lowcountry (South Carolina) – Beaufort County Library
{{Authority control Fluvial landforms Marshes, Pedology Wetlands tr:Sazlık