₦airaland Forum

WETLAND

October 05, 2018

Gabriel, J.O., Abdullahi, S., Lawal, I.I., Inuwa, F.A.,
Bello. O.R

Writes from the Department of Plant and Animal Biology,
Federal University Of Technology, Minna.

A wetland is a distinct ecosystem that is inundated by water , either permanently or seasonally, where oxygen-free processes prevail.The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants , adapted to the unique hydric soil . Wetlands play a number of roles, sometimes referred to as functions. Among these are water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, and support of plants and animals. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life.
Wetlands occur naturally on every continent.The main wetland types are swamp , marsh , bog, fen ; sub-types include mangrove forest, carr , pocosin ,floodplains ., mire, vernal pool , sink, an many others. Many peatland s are wetlands. The water in wetlands is either freshwater , brackish , or saltwater. Wetlands can be tidal (inundated by tides or non-tidal. The largest wetlands include the Amazon River basin , the West Siberian Plain , the Pantanal in South America, and the Sundarbans in the Ganges- Brahmaputra delta.
A patch of land that develops pools of water after a rain storm would not necessarily be considered a "wetland", even though the land is wet. Wetlands have unique characteristics: they are generally distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. Specifically, wetlands are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants.
Under the Ramsar international wetland conservation treaty , wetlands are defined as areas of marsh, fen , peatland or water, whether 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 whi at low tide does not exceed six metres.
In the United States Code , the term wetland is defined "as land that (A) has a predominance of hydric soils, (B) is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation typically adapted for life in saturated soil conditions and (C) under normal circumstances supports a prevalence of such vegetation."

ECOLOGY OF WETLAND
The most important factor producing wetlands is flooding. The duration of flooding or prolonged soil saturation by groundwater determines whether the resulting wetland has aquatic, marsh or swamp vegetation . Other important factors include fertility, natural disturbance, competition, herbivory , burial and salinity. When peat accumulates, bogs and fens arise.
Characteristics of wetlands
Wetlands vary widely due to local and regional differences in topography, hydrology, vegetation , and other factors, including human involvement.
Hydrology of wetland
Wetland hydrology is associated with the spatial and temporal dispersion, flow, and physio-chemical attributes of surface and ground water in its reservoirs. Based on hydrology, wetlands can be categorized as riverine (associated with streams), lacustrine (associated with lakes and reservoirs), and palustrine (isolated). Sources of hydrological flows into wetlands are predominantly precipitation, surface water, and groundwater . Water flows out of wetlands by evapotranspiration, surface runoff, and subsurface water outflow. Hydrodynamics (the movement of water through and from a wetland) affects hydro-periods (temporal fluctuations in water levels) by controlling the water balance and water storage within a wetland. Landscape characteristics control wetland hydrology and hydrochemistry . The O2 and CO 2 concentrations of water depend on temperature and atmospheric pressure . Hydrochemistry within wetlands is determined by the pH , salinity, nutrients, conductivity , soil composition, hardness , and the sources of water. Water chemistry of wetlands varies across landscapes and climatic regions. Wetlands are generally minerotrophic with the exception of bogs. Bogs receive most of their water from the atmosphere; therefore, their water usually has low mineral ionic composition. In contrast, groundwater has a higher concentration of dissolved nutrients and minerals. The water chemistry of fens ranges from low pH and low minerals to alkaline with high accumulation of calcium andmagnesium because they acquire their water from precipitation as well as ground water.

Flora of wetland
There are four main groups of hydrophytes that are found in wetland systems throughout the world.
Submerged wetland vegetation can grow in saline and fresh-water conditions. Some species have underwater flowers, while others have long stems to allow the flowers to reach the surface. Submerged species provide a food source for native fauna, habitat for invertebrates, and also possess filtration capabilities. Examples include seagrasses and eelgrass . Floating water plants or floating vegetation is usually small, like arrow arum (Peltandra virginica). Trees and shrubs, where they comprise much of the cover in saturated soils, qualify those areas in most cases as swamps .

Fauna of wetland
Fish are more dependent on wetland ecosystems than any other type of habitat. Seventy-five percent of the Unite States' commercial fish and shellfish stocks depend solely on estuaries to survive.Tropical fish species need mangroves for critical hatchery and nursery grounds and the coral reef system for food.
Reptiles such as alligators and crocodiles are common in wetlands of some regions. Alligators occur in fresh water along with the fresh water species of the crocodile.The Florida Everglades is the only place in the world where both crocodiles and alligators coexist.Snakes , lizards and turtles also can be seen throughout wetlands. Snapping turtles are one of the many kinds of turtles found in wetlands. Birds , particularly waterfowl and wading birds , use wetlands extensively.
Mammals include numerous small and medium-sized species such as voles,bats, and platypus in addition to large herbivorous and apex species such as the beaver, coypu, swamp rabbit , florida panther , and moose . Wetlands attract many mammals due to abundant seeds, berries, and other vegetation components, as well as abundant populations of prey such as invertebrates, small reptiles and amphibians. Insects and invertebrates total more than half of the 100,000 known animal species in wetlands.

Uses of wetlands
Depending partly on a wetland's geographic and topographic location, the functions it performs can support multiple ecosystem services, values, or benefits. United Nations Millennium Ecosystem Assessment and Ramsar Convention described wetlands as a whole to be of biosphere significance and societal importance in the following areas, for example:
Water storage (flood control)
Groundwater replenishment
Shoreline stabilisation and storm protection
Water purification
Reservoirs of biodiversity
Pollination
Wetland products
Cultural values
Recreation and tourism
Climate change mitigation and adaptation.
Factors Affecting Wetland
Wetlands, the function and services they provided as well as their flora and fauna, can be affected by several types of factors; These can be human-associated or natural, direct or indirect, reversible or not, and isolated or cumulative.The predominant ones include the following;
Enrichment/Eutrophication
Organic loading and reduced dissolved oxygen
Contaminant toxicity
Acidification
Salinization
Sedimentation
Altered solar input (Turbidity/Shade)
Vegetation Removal
Thermal Alteration
Dehydration/Aridification
Inundation/Flooding
Habitat Fragmentation
Other Human Presence

SOURCES
Drainage
Development
Over-grazing
Mining
Unsustainable Water Use

Conservation
Wetland have historically been the victim of large draining efforts for real estate development, or flooding for use as recreational lake or hydropower generation.some of the world's most important agricultural area are wetlands that have been converted to farmland.
Since 1970s,more focus has been put on preserving wetlands for their natural function yet by 1993 half of the world's wetlands have been drained.
In order to maintain wetlands and sustain their functions, alterations and disturbances that are outside the normal range of variation should be minimized.