Types of Wetlands

Wetlands have generally been divided under following headings –

1. Marshes – Marshes are areas with shallow water that are mostly grasslands. Marshes can be freshwater or saltwater and the amount of water in a marsh can change with the seasons and in the case of salt water marshes, can also change with the tide. Freshwater marshes have soft stemmed and herbaceous plants, like grasses and shrubs like rushes, sedges, and saltbush. Marshes are home to a variety of animals, including beavers, alligators, newts, shrimp and turtles. Marshes have soil with low mineral content. Freshwater marshes often occur along the edges of lakes and rivers. Saltwater marshes occur along coastlines, inlets and estuaries where they are affected by tides, and often have a source of fresh water from surrounding land, rivers or ground water.

2. Swamps – Swamps are slow moving streams, rivers or isolated low areas with more open and deeper water than marshes. Swamps have trees (for example, Cypress trees in freshwater and mangrove trees in salty water) and woody shrubs rather than grasses and herbs, Swamps are found in low-lying areas near rivers or coastal areas. Examples include the Sunderbans in West Bengal, Swamp soil is poorly-drained and water logged. Swamp wildlife includes alligators, snakes, insects, bobcat, beaver and large diversity of birds.

3. Bogs and Fens – A bog is a fresh water wetland, usually formed in an old glacial lake with a spongy peat base. Most of the bog’s water comes from rain. A fen is a fresh water peat wetland covered mostly by grasses sedges, reeds, and wildflowers of high pH (alkaline) ground water. Bogs have soil that is low in nutrients. Evergreen trees and shrubs, and a floor covered by a thick carpet of sphagnum moss. Some species of carnivorous plants are also found in bogs. There are only a few animals that are found in bogs. These include red deer, Dragonflies and birds such as grouse and plover.

Ramsar Convention on wetlands

The Convention on Wetlands, signed in Ramsar, Iran, in 1971, is an intergovernmental treaty which provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources. Ramsar Convention is the only global environment treaty dealing with a particular ecosystem. The Ramsar Convention Wetlands was developed as a means to call international attention to the rate at which wetland habitats were disappearing, in part due to a lack of understanding of their important functions, values, goods and services. Governments that join the Convention are expressing their willingness to make a commitment to helping to reverse that history of wetland loss and degradation.

Under the “three pillars” of the Convention, the Contracting Parties commit to:

• Work towards the wise use of all their wetlands;
• Designate suitable wetlands for the list of wetlands of international Importance (the “Ramsar List”) and ensure their effective management;
• Cooperate internationally on trans-boundary wetlands, shared wetland systems and shared species. Major obligations of countries which are party to the Convention are:
• Designate wetlands for inclusion in the list of Wetlands of International Importance.
• Promote, as far as possible, the wise use of wetlands in their territory.
• Promote international cooperation especially with regard to trans-boundary wetlands, shared water systems, and shared species.
• Create wetland reserves.

National Wetland Conservation Programme (NWCP)

Government of India operationalized National Wetland Conservation Programme (NWCP) in closed collaboration with concerned state Government during the year 1985/86. Under the programme 115 wetlands have been identified till now by the Ministry which requires urgent conservation and management initiatives.

The Scheme was initiated with the following objectives:-

• To lay down policy guidelines for conservation and management of wetlands in the country;
• To undertake intensive conservation measures in priority wetlands;
• To monitor implementation of the programme; and
• To prepare an inventory of Indian Wetlands.

Ramsar Sites of India (decreasing Area wise)

Estuaries

An estuary is a partially enclosed body of water formed where freshwater from the land meets and mixes with saltwater from the ocean. This mixing of waters with such different salt concentrations creates a very interesting and unique ecosystem. In fresh water the concentration of salts, or salinity, is nearly zero. The salinity of water in the ocean averages about 35 parts per thousand. The mixture of seawater and fresh water in estuaries is called brackish water and its salinity can range from 0.5 to 35 ppt. The salinity of estuarine water varies from estuary to estuary, and can change from one day to the next depending on the tides, weather, or other factors.

Estuaries support a wide variety of flora and fauna. Micro flora like algae, and Macro flora, such as seaweeds, marsh grasses, and Mangrove trees (only in the tropics), Can be found here. Mangroves are various large and extensive types of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes 25° N and 25° S. Estuaries support a diverse fauna, including a variety of worms, oysters, crabs, and waterfowl . Estuaries vary in size and can also be termed bays, lagoons, harbours, inlets, sounds, wetlands and swamps. Estuaries are unique environment to which plants and animals have specially adapted. They are a type of transition from land to sea and fresh water to salt water. Estuaries transport and trap nutrients and sediment through the combined action of freshwater flow, wind, waves and tidal action.

Characteristic features of Estuaries

• Estuaries and the lands surrounding them are places of transition from land to sea and freshwater to salt water.
• Estuarine environments are among the most productive on earth, creating more organic matter each year than comparably-sized areas of forest, grassland, or agricultural land.
• The tidal sheltered waters of estuaries also support unique communities of plants and animals especially adapted for life at the margin of the sea.
• Estuaries provide a calm refuge from the open sea for millions of plants and animals.

The diversity of habitats enclosed in estuaries supports enormous abundance and diversity of species e.g. fish, shellfish, lobsters, marine, reeds, sea-grasses, mangroves, algae, and phytoplankton.
The margins of the estuary contain the food webs important producers e.g. algae, eelgrass, rushes and mangroves providing a huge amount of organic matter-mashes and mangroves produce up to ten tones of plant detritus per hectare per year – considered organic factories.

Micro-organisms decompose complex organic compounds into useable forms-ammonia, nitrates and phosphates. This becomes the basic food for primary consumers like crabs, shellfish, snails, and marine worms. These burrowing invertebrates – especially sediment feeders continually turn over the deposited material.

Visiting animals from land, sea and fresh water use the estuary for feeding, breeding, spawning and as nurseries for their young. Food is abundant and easy to access because of the shallow water attracting many types of birds including gulls, ducks and wading birds.

Importance of Estuaries

• Estuaries provide us with a suite of resources, benefits, and services.
• Estuaries provide places for recreational activities, scientific study, and aesthetic enjoyment.

Thousands of species of birds, mammals, fish, and other wildlife depend on estuarine habitats as places to live, feed, and reproduce. And many marine organisms, including most commercially-important species of fish, depend on estuaries at some point during their development. Because they are biologically productive, estuaries provide ideal areas for migratory birds to rest and re-fuel during their long journeys.

They maintain water quality through natural filtration as microbes break down organic matter and sediments bind pollutants. Wetlands that fringe many estuaries also have other valuable functions. Water draining from the land carries sediments, nutrients, and other pollutants, Much of the sediments and pollutants are filtered out as the water flows through these fringing marshes. This creates cleaner and clearer water which benefits both people and marine life. Wetland soils and plants like mangroves. Sea grasses and reeds also act as a natural buffer between the land and ocean, absorbing floodwaters from land and storm surges from the ocean.

A rich array of habitats surrounds estuaries. The type of habitat is usually determined by the local geology and climate, Habitats associated with estuaries include salt marshes, mangrove forests, mud flats, tidal streams, rocky intertidal shores, reefs, and barrier beaches.

Salt Marshes – Salt marshes are a mosaic of snaking channels called tidal creeks that fill with seawater during high tides and drain during low tides. Salt marshes are covered with salt-tolerant plants, or halophytes, like salt they are flooded by seawater every day. They are marshy because their ground is composed of peat. Because salt marshes are waterlogged and contain lots of decomposing plant material, oxygen levels in the peat are extremely low-a-condition called hypoxia. Hypoxia promotes the growth of bacteria which produce the rotten-egg smell that is attributed to marshes and mud flats.

Adaptations to life in the estuary

Mangrove trees and blue crabs are some of the estuarine species that have adapted to unique environmental conditions. In almost all estuaries the salinity of the water changes constantly over the tidal cycle. To survive in these conditions, plants and animals living in estuaries must be able to respond quickly to drastic changes in salinity.

Plants and animals that can tolerate a wide range of salinities are called Euryhaline. These are the plants and animals most often found in the brackish waters of estuaries. These are, far fewer euryhaline than stenohaline organisms because it requires a lot of energy to adapt to constantly changing salinities. Organisms that can do this are rare and special. Some organisms have evolved special physical structures to cope with changing salinity. The smooth cordgrass found in salt marshes, for example, has special filters on its roots to remove salts from the water it absorbs. This plant also expels excess salt through its leaves.

Plants and animals that can be tolerate only slight changes in salinity are called stenohaline. These organisms usually live in either freshwater or saltwater environments. Most stenohaline organisms cannot tolerate the rapid changes in salinity that occurs during each tidal cycle in an estuary.

Unlike plants, which typically live their whole lives rooted to one spot, many animals that live in estuaries must change their behavior according to the surrounding waters’ salinity in order to survive. Oysters and blue crabs are good examples of animals that do this.

Disturbances to Estuaries

Estuaries are fragile ecosystems that are they susceptible to disturbance. Natural disturbances are caused by the forces of nature, while anthropogenic disturbances are caused by people. Natural disturbances include winds, tidal currents, waves, and ice. Anthropogenic disturbances include pollution, coastal development, and the introduction of non-native species to an area.

Natural Disturbances

The most prominent natural disturbances is the continual pounding of ocean waves. Waves can also dislodge plants and animals, or bury them with sediments, while objects carried by the water can crush them. Large storms are especially destructive to estuaries.

A common disturbance to estuaries in non-tropical regions is winter ice. Ice can freeze on an estuary’s shoreline, or flat freely in the water. When slabs of free-floating ice make contact with the shore, they have a scouring effect, dislodging and killing the plants and shoreline animals that lie in their path. When sheets of ice form on the shore, especially in salt marshes, they can trap plants and grass stalks inside them.

Another natural disturbance in salt marshes is the burial of vegetation by draining filling, floating plant material called wrack. Can be quite large-up to hundreds of square meters, and up to 30 cm thick. The spring high tides often move these wracks into the high marsh, where they become stranded.

Anthropogenic Disturbances

• The greatest threat to estuaries is, by far, their large-Scale conversion by draining filling, damming or dredging. These activities result in the immediate destruction and loss of estuarine habitats.
• Estuarine areas are seriously degraded by pollution. People have historically viewed estuaries and waterways as places to discard the unwanted by-products of civilization. Pollution is probably the most important threat to water quality in estuaries. Poor water quality effects most estuarine organisms, including commercially important fish and shellfish.
• The pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.
• Another, less widely discussed human-caused disturbance is the introduction of non-native or invasive species into estuarine environments.