36 Wet Lands- I

1. What are wetlands? 

2. The Ramsar Convention

2.1 Criteria for Identifying Wetlands of International/National Importance

2.2 Advantages of joining Ramsar Convention

2.3 Currents Status of the convention

3.Characteristics

4. Types of wetlands

5. Importance of Wetlands

6. Functions of Wetlands

1. What are wetlands?

Wetlands are neither just land nor just water i.e. these are areas where water and land are mixed. They usually occur between dry land and deep water habitats. In other words, they are transitional zones between land and water where the flow of water, cycling of nutrients and energy of the sun produce a rich variety of plants and animals. Since these are transition zones, these support both aquatic and terrestrial species. The presence of shallow water creates environment that allow the growth of plants (hydrophytes) adapted to such conditions. These are considered the most productive ecosystems on the Earth. These provide many important services to humans and environment. Wetlands can look very different throughout the world. Wetlands vary widely due to difference in climatic conditions, hydrology, water chemistry, soil types, topography, vegetation and other environmental factors. Wetlands are found through the globe from the tundra to the tropics. As per Millennium Ecosystem Assessment estimates, wetlands cover 7% of the earth’s surface and deliver 45% of the world’s natural productivity and ecosystem services. However, the existence of these valuable resources is under threat due to anthropogenic activities and calls for need to preserve and conserve these resources. Pantanal is the Largest Wetland in the world situated in Brazil to South America and covers an area of 150,000km2. Wetlands have been defined differently by different agencies in the world. Some of the definitions are:

Definition

According to most widespread definition wetlands are defined as: “lands transitional between terrestrial and aquatic eco-systems where the water table is usually at or near the surface or the land is covered by shallow water”.

USEPA defines wetlands as “areas where water covers the soil, or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season”.

World wildlife organization defines wetland “a place where the land is covered by water, either salt, fresh or somewhere in between. Marshes and ponds, the edge of a lake or ocean, the delta at the mouth of a river, low-lying areas that frequently flood—all of these are wetlands”.

Ramsar Convention on Wetlands define wetlands 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 which at low tide does not exceed six metres”.

2. The Ramsar Convention

The Ramsar Convention also known as “The Convention on Wetlands”, was adopted on 2nd February, 1971 in Ramsar, Iran. It is an intergovernmental treaty which provides the framework for national action and international co-operation for the conservation and wise use of wetlands and their resources. As per this Convention definition most of the natural water bodies (such as rivers, lakes, coastal lagoons, mangroves, peat land, coral reefs) and manmade wetlands (such as ponds, farm ponds, irrigated fields, sacred groves, salt pans, reservoirs, gravel pits, sewage farms and canals) constitute the wetland ecosystem. The Convention’s mission is “the conservation and wise use of wetlands by national action and international cooperation as a means to achieving sustainable development throughout the world”

2.1. Criteria for Identifying Wetlands of International/National Importance

Broadly the convention has 2 groups and 9 criteria’s for recognizing a wetland under this convention (source: envfor.nic.in/divisions/csurv/WWD_Booklet.pdf). These are: Group A: Sites containing representative, rare or unique wetland types

Criterion 1: It recognizes those sites of national/international importance which contains a representative, rare, or unique example of a natural or near-natural wetland type found within the appropriate biogeographic region.

Group B: Sites of international importance for conserving biological diversity-Criteria based on species and ecological communities

Criterion 2: A wetland should be considered internationally/nationally important if it supports vulnerable, endangered, or critically endangered species or threatened ecological communities.

Criterion 3: A wetland should be considered internationally/nationally important if it supports populations of plant and/or animal species important for maintaining the biological diversity of a particular biogeographic region.

Criterion 4: A wetland should be considered internationally/nationally important if it supports plant and/or animal species at a critical stage in their life cycles, or provides refuge during adverse conditions.

Specific criteria based on water birds

Criterion 5: A wetland should be considered internationally/nationally important if it regularly supports 20,000 or more water birds.

Criterion 6: A wetland should be considered internationally/nationally important if it regularly supports 1% of the individuals in a population of one species or subspecies of water bird.

Specific criteria based on fish

Criterion 7: A wetland should be considered internationally/nationally important if it supports a significant proportion of indigenous fish subspecies, species or families, life-history stages, species interactions and/or populations that are representative of wetland benefits and/or values and thereby contributes to global biological diversity.

Criterion 8: A wetland should be considered internationally/ nationally important if it is an important source of food for fishes, spawning ground, nursery and/or migration path on which fish stocks, either within the wetland or elsewhere, depends.

Specific criteria based on water/life and culture

Criterion 9: A wetland should be considered internationally/nationally important if it is an important source of food and water resource, increased possibilities for recreation and eco-tourism, improved scenic values, educational opportunities, conservation of cultural heritage (historic or religious sites).

2.2.  Advantages of joining Ramsar Convention

• Provides access to financial aid for conservation of wetlands.
• Increased publicity of the site at the international level.
• Encourages international cooperation and increases availability of expert advice and latest information on site-related problems of wetland conservation and management.
• Provides an opportunity for learning the best global practices for wise use of wetlands.
• Opportunity for getting international guidelines on various wetland conservation themes.

2.3. Currents     Status     of     the     convention:       as     on       February       2018       (as per https://www.ramsar.org)

• It has been signed by 169 countries.
• It recognizes 2331 wetland sites all over the world.
• It covers an area of nearly 225 million hectares.
• India has 26 wetlands of International Importance.
• The Ramsar Convention Secretariat carries out the day-to-day co-ordination of the Convention’s activities.
• The Ramsar Convention Secretariat is located in Gland, Switzerland.
• “World Wetlands Day” is celebrated on 2nd February every year.

3. Characteristics common to all wetlands:

• Depth: The depth of the wetlands should not exceed 6 metres.
• Water: The top 12 inches of soil must be saturated with water for at least 15 days for an area to be classified as a wetland. There sources of water may be surface water (ponds, lakes, streams, rivers, and oceans) or Ground water. The amount of water should be enough to support wetland vegetation.
• Soils: The soil is mostly hydric, because the spaces between soil particles are filled with water. Soils are anaerobic i.e. the soil lacks oxygen. The color of wetland soils is usually dark brown to black due to the presence of mineral or organic matter. These soils may smell like rotten egg due to the presence of sulfur.
• Productivity: Wetlands are among the most productive ecosystems of the world, comparable to rain forests and coral reefs. They are also known as “Biological Supermarkets”.
• Vegetation: The vegetation specifically adapted to live in an area that is saturated with water and has reducing conditions is present e.g. water lilies, arrowheads, duckweeds, pondweeds, etc. Saltwater wetland plants have special adaptations that allow them to tolerate salt. Plants in wetland are called hydrophytes.
• Earth Coverage: Wetlands are found from Tundra to Tropics and on every continent except Antarctica. They cover an area of about 570 million hectares which accounts for 6% of the earth’s land surface.

4.Types of wetlands:

• The wetlands differ due to variations in soil, landscape, climate, water quality, vegetation etc.
• The 2 general categories of wetlands are:
• Tidal or coastal wetlands: As the name suggests these are found along the oceans and sea coasts where sea water mixes with fresh water which includes estuaries. These type of wetlands are characterized by the fluctuating salty water levels (depend on tide action) and grassy vegetation that adapt to the saline conditions.
• Non-tidal or inland wetlands: These are wetlands either on floodplains along rivers, streams, lakes, ponds etc. or low lying areas where the groundwater comes out of soil surface or where rainfall sufficiently saturates the soil. Many of these wetlands are seasonal in nature.

4.1. Classification of Wetlands

Broadly 2 types of classification systems are used for wetlands.

i)  Hydrogeomorphic Classification

ii)  Cowardin system

i) Hydrogeomorphic Classification: This classification system was introduced by Brinson in 1993. This classification system is based on the concept of position in the landscape, their source of water, and the flow of water. The classification system recognizes 7 major classes, and further subdivided into subclasses. The following definitions’ are modification from Brinson et al., 1993 and Smith et al., 1995:

a) Riverine: Wetlands within river and stream channels i.e. lie adjacent to rivers and streams are called Riverine. These are characterized by flowing water having salinity <0.5 part per thousand. These are mostly found in flood plains and riparian corridors along the stream channels. The sources of water are overbank flow from channel or subsurface hydraulic water, inter flow and return flow from adjacent uplands, tributary inflow and precipitation.

b) Depressional: As the name indicates, these are located in topographic depressions where surface water from precipitation, and both interflow and overland flow from adjacent uplands can accumulate. These wetlands may lose water due to drainage from outlets, evapo-transpiration and contribution to ground water. Peat deposits may develop in these wetlands. The common example of depressional wetlands is Prairie potholes.

c) Slope: These normally occur on sloping land where there is a discharge of ground water to the land surface. These are not capable of holding water for long as these do not have well defined contours. The water sources are ground water return flow, interflow from surrounding uplands and precipitation. The common example of slope wetlands is Fens.

d) Mineral Soil Flats: These occur in floodplain terraces, relic lake bottoms or inter stream uplands and are primarily fed by precipitation. Their size varies significantly from 10 acres to thousands of acres. They can be distinguished from DEPRESSIONAL and SLOPE wetlands as these do not receive any ground water discharge. They lose water due to evapo-transpiration, saturation overland flow, and ground water seepage. Mineral soil flats that accumulate peat can eventually become the class ORGANIC SOIL FLATS. Pine flat woods with hydric soils are a common example of MINERAL SOIL FLAT wetlands.

e) Organic Soil Flats: These are also called extensive peatlands. These differ from mineral soil flats, in part, because their elevation and topography is controlled by vertical accretion of organic matter. They are located commonly on flat interfluves. These may also be found where depressions have been filled with peat to form a large flat surface. The sources of water are dominantly precipitation. The water loss is by saturation overland flow and ground water seepage. The common examples of organic soil flat wetlands are Portions of the Everglades and northern Minnesota peatlands.

f) Estuarine Fringe: Estuarine or tidal fringe wetlands are located between the open saltwater of the bays or Gulf and the uplands of the coastal plain and barrier islands. These may be vegetated (marshes) or unvegetated (mud and sand flats). These occur in strips of varying sizes from few feet to several miles wide. The dominant water sources are tidal currents & river flow and additional are ground water discharge and precipitation. The common examples of estuarine fringe wetlands are Spartina alterniflora salt marshes.

g) Lacustrine Fring: These wetlands are located adjacent to lakes and may consist of a floating mat attached to land. The sources of water are elevation of the lake water, precipitation and ground water discharge. Surface water flow is bidirectional and is controlled by water-level fluctuations in the adjoining lake. These wetlands are nearly similar to depressional wetlands. These wetlands lose water by flow returning to the lake after flooding, ground water seepage and evapo-transpiration. The common example of lacustrine fring is E wetlands Unimpounded marshes bordering the GreatLakes.

ii)  Cowardin   system:   The   system   of   classification   was   developed   by   Lewis M. Cowardin et al., in 1979. This system of classification is based on four different factors:

•  Types of vegetation present
•  Pattern of flooding
• Chemistry of the water
• Type of soil

On the basis of these factors, the wetlands have been classified into 5major types:

a) Marine wetland or coastal wetlands: These are areas exposed to the open ocean. These include coastal lagoons, rocky shores and coral reefs.

b)Estuarine wetland: These are partially enclosed by land exposed to a mixture of fresh and salt water bodies of water. These include deltas, tidal marshes and mangrove swamps.

c)Riverine wetlands: These include wetlands along rivers and streams.

d) Lacustrine (Lake) wetland: These are wetlands associated with the lakes.

e) Palustrine wetlands: These are freshwater wetlands not associated with a river or lake. It means “marshy” including marshes, swamps and bogs.

In addition to these there are human-made wetlands such as fish and shrimp ponds, farm ponds, etc. Some common subtypes of wetlands are described below.

Marshes: It is a wetland characterized by dominant herbaceous plants rather than woody plant species. These form a transition between the aquatic and terrestrial ecosystems and are located at the edges of lakes and streams. They are often dominated by grasses, rushes or reeds. These can be of many kinds ranging from the freshwater to saltwater, coastal to inland,prairie potholes to the Everglades etc. These are rich in nutrients and the pH is usually neutral. This supports wide variety of plant and animal life. Depending on the basis of their location and salinity, marshes can be subdivided as salt marshes, freshwater tidal marshes and freshwater marshes. These three further contains a different set of plants and animals.

Saltwater marshes: These are marshes located close to the coastal shoreline where the motion of the tides affects them. These are mostly found in lagoons, estuaries, etc. The nutrients are absorbed from the water returning back after tides. These are dominated by salt-tolerant grasses [Cord grass, Spike Grass and Salt meadow Rush (Juncus gerardii)] and specially adapted rooted vegetation.

Fresh water tidal marshes: They are mostly freshwater marshes occasionally affected by the ocean tides. Water levels in these wetlands generally vary from a few inches to 2-3 feet. The diversity of the plants and animals in these marshes is much higher than in salt marshes.

Fresh water marshes: They frequently occur along the boundaries of lakes, ponds and rivers. These are poorly drained and some of these may periodically dry out completely. These are rich in organic matter and nutrients. The common plants and animals present are lily pads, cattails, reeds, bulrushes, and waterfowl, Red-winged Blackbirds, Great Blue Herons, otters, muskrats etc. The examples of these marshes are Prairie potholes, playa lakes, vernal pools and wet meadows.

Swamps: Swamps are forested wetlands dominated by woody plants and bushes. These are located near rivers or lakes and have mineral soil that drains very slowly. The soils in swamps may or may not be rich in nutrients. The swamps having highly organic soils form a thick, black, nutrient-rich environment for the growth of water tolerant trees like Cypress (Taxodium spp.), Atlantic White Cedar (Chamaecyparis thyoides), and Tupelo (Nyssa aquatica). Other swamps are dominated by shrubs, such as Buttonbush or Smooth Alder. These are rich in biodiversity and support variety of plants, birds, fish, and invertebrates such as freshwater shrimp, crayfish, and clams. These are also the habitat of many rare/endangered species, such as American Crocodile. Swamps may be divided into shrub swamps and forested swamps depending on the type of vegetation present. These are further classified by the types of trees growing there.

Further, it has been hypothesized that ancient swamps are a source of the fossil fuel coal. Coal is formed from plants which died and decayed in the absence of oxygen millions of years ago. The pressure of upper layers for million years caused the vegetation to harden, or fossilize into coal.

Bogs: The bogs are freshwater wetlands which have soft spongy ground consisting mainly of partially decayed plant matter called peat mosses. The source of water is precipitation and hence do not receive nutrients from runoff and are low in nutrients. The water table is close to the ground surface. The dead plant matter makes sphagnum moss and wire due to oxygen-starved conditions. Hence, bogs become choked with living and decaying plants. These slowly decaying plants become the main components of the bog’s soggy soil, called histosol which supports the growth of fungi and low-lying shrubs, such as heather. Hence such bogs are often called “heaths”. Sometimes, a bog is entirely covered with the sphagnum moss which prevents precipitation from evaporating. Such bogs are called ombrotrophic bogs. They are characterized by spongy peat deposits, acidic waters and a floor covered by a thick carpet of sphagnum moss.

Fens: These are peat forming wetlands with low to moderate fertility and are fed by both groundwater and surface runoff. These receive the nutrients through drainage from surrounding mineral soils and from groundwater movement. These differ from bogs being less acidic and higher nutrient levels. Hence, these support a diverse plant and animal community. They share some of the features of low fertility bogs as well as higher fertility swamps. These wetlands are dominated by grasses, sedges, rushes and wildflowers. Some fens are characterized by parallel ridges of vegetation separated by less productive hollows. The deposition of peat over long time may separate the fen from its water supply and hence nutrients. This may ultimately be converted into a bog.

5.  Importance of wetlands

Wetlands are very important for the ecological balance of the earth and human survival. The wetlands are among the world’s most productive environments. They are cradles of biological diversity. They support a high concentration of birds, mammals, reptiles, amphibians and fish. Important storehouse of plant genetic material e.g. rice, a wetland plant is a staple diet of more than half of humanity. Wetlands also support human settlements and play important role in sustainability of resources. We need to save the wetlands due to their importance/benefits for humans. The importance/benefits of wetlands are as follow.

Water Quality

The wetlands act as filter of sediments, nutrients, pollutants, microorganisms etc. which flow through water runoff from human settlement, roads, agriculture, industrial effluents. Hence these are called “Treatment wetlands”. Such wetlands are even specifically constructed to improve surface water quality and to treat storm water runoff.

Flood Control

Wetlands act as reservoirs of extra water and hence control the floods. This results in more gradual discharges of water over a longer period of time. This also protect the downstream property of owners from flood damage.

Reduce Erosion

One of important function of wetland is its ability to slow the movement of upland runoff. This allows for settlement of excess nutrients and sediment in wetlands. The excess nutrients can be absorbed by aquatic vegetation. The plants growing along the shores/banks of rivers, streams and lakes reduce soil erosion. The plants reduce erosion by holding the soils with their roots and slowing water currents.

Groundwater Recharge

Wetlands are essential components of the water cycle. They provide link between ground and surface water. The wetlands on one side act as reservoir for extra water and on other side allow the water to continuously seep down to recharge the water table. This water recharge helps to maintain water quality and groundwater supplies, especially during dry periods. These also contribute to atmosphere moisture, humidity and influence rainfall patterns.

Habitat

Wetlands are the natural habitat for many species of plants, animals, mammals, reptiles, bird, fish, amphibians and invertebrates. These are the natural homes of many specific species which are found only in wetlands. These provide food, shelter, breeding and resting places for the biodiversity. As per some reports, wetlands provide critical habitat for about one-third of all threatened or endangered animal species in North America.

Recreation and Tourism

Wetlands are popular places for recreation such as bird watching, photography, canoeing, relaxation, cultural and tourism. People usually visit these areas to observe wildlife and nature. Boating and fishing is common in many wetlands. This also provide economic benefits to the locals.

6. Functions of wetlands:

• Water storage and stream flow
• Drought relief
• Flood peak reduction
• Soil erosion protection
• Sediment accretion
• Water quality improvement
• Wildlife protection
• Socio economic benefits
• Recreational and educational opportunities
• Agricultural production
• Global climate control
• Wetland medicines