Wetlands

Wetland is a type of Habitat or Biome whose land mass is saturated with moisture either permanently or seasonally. Wetlands can be covered partially or completely by shallow pools of water. Although Wetlands are often wet, a Wetland might not be wet year-round. In fact, some of the most important Wetlands are only seasonally wet. Wetlands are the link between the land and the water. They are transition zones where the flow of water, the cycling of nutrients, and the energy of the sun meet to produce a unique ecosystem characterized by hydrology, soils, and vegetation. Wetlands can be natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres. Wetlands make up 6% of the Earth's surface. 14 % of the World's Wetlands are located in Canada. An acre of Wetland can store 1–1.5 million gallons of flood water. A Wetland one mile deep can reduce storm surge by 1 to 1.5 feet.

1.  Classification / Types of Wetlands based on Tidal Activity

Tidal Wetlands - Wetlands where the land meets the Sea are known as Tidal Wetlands. These areas are periodically flooded by sea water during high or spring tides or, are affected by the cyclic changes in water levels caused by the tidal cycle. Tidal Wetlands are not limited to Banks, Bogs, Salt Marshes, Swamps, Meadows and Flats. They are also known as Coastal or Estuarine Wetlands.

Non-Tidal Wetlands - Non-Tidal Wetlands occur along streams in poorly drained depressions, and in the shallow water along the boundaries of Lakes, Ponds, and Rivers. They are inland, freshwater areas not subject to tidal influence and are usually covered or saturated with water for long periods during the growing season. They are also known as Freshwater, or Palustrine Wetlands. Non-tidal Wetlands may occur far from Rivers or Creeks as well.

2.  Types of Wetlands based on Vegetation and Location

Bogs - Bogs are Freshwater Wetlands often formed in old Glacial Lakes, characterized by Spongy Peat deposits, evergreen Trees and Shrubs, and a floor covered by a thick carpet of Sphagnum Moss. When large chunks of Glacial ice is left behind by retreating Glaciers, they may be surrounded by sediments flowing out of these melting Glaciers. When these chunks of ice melt, the depressions that form, turn into Bogs if the water retained there does not drain out. Bogs have acidic water and floating Mats form from partly-decayed Plant material. The Mats start at the shore and grow inward, eventually covering the entire Bog. These Mats are very interesting places with unique Plant communities, including Sphagnum Mosses which add to the acid levels in the Bog. Eventually the Mat fills in the entire Bog. Many well-preserved skeletons of ice-age Animals such as woolly Mammoths and Mastodons have been discovered in filled-in Bogs that have been mined for Peat, which is the stuff from the old Bog Mat.

Fens - Fens are freshwater peat-forming Wetlands covered mostly by Grasses, Sedges, Reeds and Wild Flowers. Fens are unusual as they form when water seeps through alkaline soils (containing limestone or its related minerals) into depressions along gentle slopes found in the sediments left behind by melting Glaciers. The water in Fens is alkaline, and Plants living there must be adapted to these alkaline conditions. Fens are less acid and more mineral-rich than are Bogs.

Swamps - Swamps are Wetlands which get flooded seasonally flooded. They have more woody Plants than a Marsh and better drainage than a Bog. They are also known as Forested Wetlands due to the presence of large number of Trees. These Wooded Wetlands are dominated by 25% or greater cover of Trees or tall Shrubs. The most common Trees in a Swamp may include Pin Oaks, Swamp White Oaks, and Red Maple. Other trees such as Tupelo, Sycamore, Cottonwood, and American Elm are also often found. Shrubs include Elderberry, Swamp Rose and European Buckthorn.

Marshes - Marshes are open Wetlands without Trees. They are dominated by soft-stemmed vegetation. Common Plants in marshes include Cattails, Sedges, and Rushes. A number of Grasses are found in marshes as well. Marshes are rich in wildlife, including many Birds and Mammals like Mink, Raccoon and Muskrat.
 
Vernal Pools - Vernal Pool is a type of a Wetland that receives most of its water from precipitation.These are temporary Ponds that fill with water during the spring rains and floods, but which dry up later in the summer or fall. They are very important for a number of Wildlife Species, including Amphibians like Frogs, Toads, and Salamanders, which don't live in them year-round but need these pools to breed and lay eggs.

3.  Types of Wetland according to Ramsar Classification System

Marine / Coastal Wetlands - A Coastal Wetland is an area that has wet and spongy soils, and is located in the transition zone between dry land and the Ocean. Examples of Coastal Wetlands are Marshes, Swamps, or Bogs. Coastal Wetlands are home to various number of Fish, Shellfish, Blue Crabs, Shrimps etc.

Inland Wetlands - Inland Wetlands form along Rivers and Streams, in isolated depressions surrounded by dry land, along the margins of Lakes and Ponds, and in other low-lying areas where the ground water intercepts the soil surface or where precipitation sufficiently saturates the soil.

Human-Made Wetlands - Human-Made Wetlands are are artificial as they have been built by humans. These do not occur naturally rather they are created to treat waste water. Human-Made Wetland may consists of 50% chip bark, 20% gravel, 15% sand, and a miscellaneous amount of straw, peat moss, sewage sludge and aged manure. They maybe constructed for breeding Fish and other Aquaculture activities.

These are further subdivided by the type of water: fresh / saline / brackish / alkaline; and may be further classified by the substrate type of other characteristics.

Distribution

Wetlands are found all over the World. The only Continent that does not have Wetlands is Antarctica.

Some Major Wetlands of the World

• Pantanal in Brazil.

• Danube River Delta in Europe.

• Sundarbans in India and Bangladesh.

• Kafue Floodplains in Zambia.

• Okavango in Botswana.

General Characteristics of Wetlands

• Formation in Low Lying Areas - Wetlands form when water collects in a low-lying area. Wetlands occur in depositional settings where geological and/or geomorphological controls limit stream incision and create accommodation space where sedimentation is likely to occur. The water that fills Wetlands comes from many sources. Precipitation is a major source of water for many Wetlands. Other Wetlands are maintained by water that periodically overflows rivers, lakes, etc. A third source of water for Wetlands is groundwater- water that flows underground and sometimes emerges at the surface of the soil. The land is flat and Moreover the surface of a Wetland is mostly flat and water runs off the surface very slowly, enabling the storage of water. A Wetland may seem dry at the surface, but if one digs down six inches or a foot, one finds that the soil is waterlogged below the surface.

• Shallow Water Habitat - Wetlands have shallow water in them. The depth of Wetlands vary but they are deep enough to support a host of aquatic and amphibian life form. Shallow water areas provide habitat for microscopic Plants and Animals like Bay Grasses, Worms, Snails, Clams, Crabs, Fish, Frogs, Turtles, Muskrats, Shorebirds and Waterfowl. These use shallow water areas as nursery areas and for protection from predators. Migratory water Birds and Waterfowl, Wading birds like Herons and Egrets, Shorebirds like Terns and Gulls, and Raptors like osprey and Bald Eagles feed in the shallows.

• Hydric Soil - Hydric means excessive moisture. Wetlands are lands made up of Hydric Soil. A Hydric Soil is a soil that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. Wetland soils are often clay-like and allow very little movement of water through them. Sometimes Wetland soils are mostly organic (made of partly-decayed plant parts such as leaves and stems). Wetland soils are usually blackish, greyish, or even greenish, rather than the reddish or brown soils found in drier areas. These colors are due to chemical reactions that have to do with the absence (in wetland soils) or presence (in drier soils) of oxygen. Oxygen is mostly absent in Wetland soils because they are usually soaked with water, rather than having the spaces between the soil particles holding air.

• Poor Drainage of Water - Wetlands are characterised by having poor drainage of water. The water in a Wetland is stationary as the soil is clay like and is tightly packed making the soil like a sold surface disabling proper drainage of water. The water therefore has enough supply of minerals to stimulate decay of organisms and prevent the accumulation of organic materials.

• Hydrophytic Vegetation - Wetland Plants have evolved from terrestrial (dry land) ancestors, and have evolved adaptations that let them live with their roots (or sometimes the entire plant) in water or water-soaked soil. One common adaptation of non-woody Wetland Plants is Aerenchymous (air-filled) tissues. This tissue is spongy because it contains many special tubes that lead down from the green parts of the Plant, where oxygen is produced during photosynthesis, to supply the roots with oxygen, is where it is constantly being used up by respiration. Some Plants, like Buttonbush, have evolved ways of breaking sugar apart without using oxygen. Plants such as Elodea, Eelgrass, and Coontail, which grow entirely under water have other adaptations that allow them to survive in these aquatic environments. Not all Wetland Plants grow only in Wetlands; some prefer Wetlands but can grow elsewhere, and are called 'Facultative' (having the ability to do a certain thing). Those which must grow in Wetlands are called Obligate (having to do something). Plant life found in Wetlands includes Mangrove, Water Lilies, Cattails, Sedges, Tamarack, Black Spruce, Cypress, Gum, and many others.

• Biological Diversity of Animals - Wetlands are among the World’s most productive environments. They are cradles of biological diversity, providing the water and primary productivity upon which countless Species of Plants and Animals depend for survival. They support high concentrations of Birds, Mammals, Reptiles, Amphibians, Fish and various Invertebrate Species. These includes many different Amphibians, Reptiles, Birds, Insects, And Mammals. Some of the Wetland specialist Animals are Turtles, Frogs, Snakes, Alligators, Crocodiles, Frogs and Salamanders. These act as temporary grounds for breeding. Migratory Birds use Wetlands to rest and feed during their cross-continental journeys and as nesting sites when they are at home.

Origin of Wetlands

When land Plants evolved and diversified, different Wetland types began to appear. The first Marshes developed in the mid-Devonian Period (405 million to 345 million years ago), and Forest Swamps originated in the Late Devonian. Adaptations to low-oxygen, low-nutrient conditions allowed for the evolution of Fens and Forest Mires (peat forests) in the Late Devonian. The differentiation of Wetland Habitats created varied niches that influenced the terrestrialization of Arthropods in the Silurian Period (425 million to 405 million years ago) and the terrestrialization of Tetrapods in the Devonian Period, and dramatically altered the way sedimentological, hydrological, and various biogeochemical cycles operated globally. Widespread peat-lands evolved in the Carboniferous (345 million-280 million years ago), with the earliest ombrotrophic tropical Mires arising by the early Late Carboniferous Period . Although widespread at the end of the Paleozoic (544 million-230 million years ago), peat-forming Wetlands virtually disappeared following the end-Permian extinction.

Importance of Wetlands

• Wetlands provide habitat for many Plants and Animals. Various Species of Animals, Trees, Shrubs, Grasses, Sedges, Rushes, Orchids, Water Plants, and Wild Flowers are totally dependant on Wetlands for their survival. Even those Animals which do not live in Wetlands need them for feeding, breeding, resting or safety.

• Wetlands are Nature’s water filters as they a key role in keeping the water clean. There are many types of Plants and Animals which remove many harmful impurities. As water slowly seeps through Wetlands, the Plants living there filter out much of the human-made pollutants (like pesticides from farms, and industrial chemicals) that reaches the groundwater. Some of these pollutants are trapped in the soils and Plants; some chemicals are altered in a way that they are no longer harmful. Wetlands also absorb fertilizers that run off farmlands. In fact, Artificial Wetlands have been created to treat waste water in Europe for over 50 years. Several communities and businesses in Canada now use Wetlands to treat their waste water.

• Wetlands help in controlling floods. Often, spring run-off and heavy rain can cause flooding. There is simply too much water for the landscape to absorb. Wetlands act like sponges during periods of flooding, and they hold a lot of the water, letting it drain into rivers and streams slowly, instead of all at once.

• Wetlands prevent and slow down the process of soil erosion. The Wetland Plants stabilize the soil, holding it in place against erosive forces. Wetlands at the margins of Lakes, Rivers, Bays, and the Ocean  protect shorelines and stream banks against erosion. Wetland Plants hold the soil in place with their roots, absorb the energy of waves, and break up the flow of stream or river currents. The ability of Wetlands to control erosion is so valuable that some countries are restoring Wetlands in coastal areas to buffer the storm surges from hurricanes and tropical storms. Furthermore, Wetlands slow down the erosion of soil from farmed fields in the springtime, which not only saves the top soils for farmers, but also prevents the water in rivers and streams from getting all murky which makes it unsuitable for the organisms living in it.

• Wetlands help supply water in times of drought. Since Wetlands hold water and prevent it from running off into streams right away, they are always be wet even when periods of drought begin. This water in Wetlands has more of a chance to seep into the ground and so will help keep the water table up during drought periods. This benefits farmers and people who get their drinking water from wells. Wetlands help to replenish groundwater. As Wetlands store excess water, they release it back into the environment. Water held in Wetlands seeps slowly back into the ground and is purified and filtered providing people with clean water.

• Wetlands are like outdoor classrooms for students and laboratories for researchers as Wetlands are practical chapters of a lesson in book. Students can actually witness and learn what they have only heard or seen in books. Researchers benefit from the whole functioning of a Wetland as an ecosystem.

• Wetlands are places for various leisure and sports activities like hiking, wildlife watching, hunting, angling, camping, canoeing etc. These activities also attracts Tourists which provides funds to the local community as well as the country's exchequer.