Marshes develop along the edges of rivers and lakes. A patch of land that develops pools of water after a rainstorm would not necessarily be considered a wetland, even though the land is wet. 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. Wetlands have also been described as ecotones, providing a transition between dry land and water bodies.
A wetland is «an ecosystem that arises when inundation by water produces soils dominated by anaerobic and aerobic processes, which, in turn, forces the biota, particularly rooted plants, to adapt to flooding.
Wetlands are adept at impacting the water chemistry of streams or water bodies that interact with them and can withdraw ions that result from water pollution such as acid mine drainage or urban runoff.
The chemistry of water flowing into wetlands depends on the source of water and the geological material in which it flows through as well as the nutrients discharged from organic matter in the soils and plants at higher elevations in slope wetlands.
Animals Living in Wetlands
Many species of frogs live in wetlands, while others visit them each year to lay eggs. Snapping turtles are one of the many kinds of turtles found in wetlands. Fish are more dependent on wetland ecosystems than any other type of habitat. Reptiles such as alligators and crocodiles are common in wetlands of some regions.
Snakes, lizards, and turtles also can be seen throughout wetlands. Birds, particularly waterfowl and wading birds, use wetlands extensively. 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.
Invertebrates of wetlands include aquatic insects, crustaceans, mollusks, and worms, among others. Invertebrates comprise more than half of the known animal species in wetlands and are considered the primary food web link between plants and higher animals. The low oxygen conditions in wetland water and their frequent flooding and drying prevent many invertebrates from inhabiting wetlands, and thus the invertebrate fauna of wetlands is often less diverse than some other kinds of habitat. Some wetland invertebrates thrive in habitats that lack predatory fish.
Many insects only inhabit wetlands as aquatic immatures and the flying adults Inhabitat upland habitats, returning to the wetlands to lay eggs.
Due to their productivity, wetlands are often converted into dry land with dykes and drains and used for agricultural purposes. The construction of dykes, and dams, has negative consequences for individual wetlands and entire watersheds.
Because wetlands are indicative of the amount of water in the soil, they are found all throughout the world in different climates. Many of the world’s wetlands are in temperate zones, midway between the North or South Pole and the equator. Wetlands in the tropics are much warmer for a larger portion of the year. Wetlands on the Arabian Peninsula can reach temperatures exceeding 50 °C and would therefore be subject to rapid evaporation.
Wetlands close to the headwaters of streams and rivers can slow down rainwater runoff and spring snowmelt so that it doesn’t run straight off the land into watercourses.\ Water management engineering developments in the past century have degraded these wetlands through the construction of artificial embankments. Wetland water sources that were once spread slowly over a large, shallow area are pooled into deep, concentrated locations. Loss of wetland floodplains results in more severe and damaging flooding.
The surface water which is the water visibly seen in wetland systems only represents a portion of the overall water cycle which also includes atmospheric water and groundwater. Wetland systems are directly linked to groundwater and a crucial regulator of both the quantity and quality of water found below the ground. Wetland systems that are made of permeable sediments like limestone or occur in areas with highly variable and fluctuating water tables especially have a role in groundwater replenishment or water recharge. Wetlands can also act as recharge areas when the surrounding water table is low and as a discharge zone when it is too high.
Shoreline stabilization and storm protection
Some aquaculture has eliminated massive areas of wetland through practices seen such as in the shrimp farming industry’s destruction of mangroves. Threats to rice fields mainly stem from inappropriate water management, the introduction of invasive alien species, agricultural fertilizers, pesticides, and land-use changes. Industrial-scale production of palm oil threatens the biodiversity of wetland ecosystems in parts of southeast Asia, Africa, and other developing countries. Over-exploitation of wetland products can occur at the community level as is sometimes seen throughout coastal villages of Southern Thailand where each resident may obtain for themselves every consumable of the mangrove forest which then becomes threatened through the increasing population and continual harvest.
Prescribed natural regeneration
There is no biophysical manipulation and the ecosystem is left to recover based on the process of succession alone. In order for this type of restoration to be effective and successful, there must be prior research done to understand the probability that the wetland will recover with this method.
In these circumstances, the wetland is impaired and without human assistance, it would not recover within an acceptable period of time determined by ecologists. Again these methods of restoration will have to be considered on a site-by-site basis as each site will require a different approach based on levels of disturbance and ecosystem dynamics.
In the United States, wetlands are defined as «those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas. Wetlands can be dry during the dry season and abnormally dry periods during the wet season, but under normal environmental conditions, the soils in a wetland will be saturated to the surface or inundated such that the soils become anaerobic, and those conditions will persist through the wet portion of the growing season.