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ECOLOGY OF WETLANDS AND ITS MANAGEMENT STRATEGIES

Dr. Subhendu Datta, Sr. Scientist

subhdatta@yahoo.com

INTRODUCTION

Wetlands are complex and fascinating ecosystems that perform a variety of functions of vital

importance to the environment and to the society whose very existence depends on the quality

of the environment. Wetlands regulate water flow by detaining storm flows for short periods

thus reducing flood peaks. Wetlands protect lakeshore and coastal areas by buffering the

erosive action of waves and other storm effects. Wetlands improve water quality by retaining or

transforming excess nutrients and by trapping sediment and heavy metals. Wetlands provide

many wildlife habitat components such as breeding grounds, nesting sites and other critical

habitat for a variety of fish and wildlife species as well as the unique habitat requirements of

many threatened and endangered plants and animals. Wetlands also provide a bounty of plant

and animal products such as blueberries, cranberries, timber, fiber, finfish, shellfish, waterfowl,

furbearers and game animals. Although wetlands are generally beneficial, they can, at times,

adversely affect water quality. Waters leaving wetlands have shown elevated coliform counts,

reduced oxygen content and color values that exceed the standard for drinking water.

While many wetland functions are unaffected by land management activities, some

functions can be compromised or enhanced by land management activities. Deforestation, for

instance, can reduce or eliminate the ability of a wetland to reduce flood peaks. On the other

hand, retaining forest vegetation on a wetland can help retain the ability of the soil to absorb

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runoff water thus reducing peak flood flows. In addition, management of the forest can actually

improve wildlife habitat and produce revenue to offset the cost of retaining the wetland for

flood control. The key is to recognize environmental values and incorporate them into

management decisions.

DEFINITION

The term "wetlands" includes a variety of transitional areas where land based and water based

ecosystems overlap. Our language is filled with many descriptive terms for wetlands. Even if

you've never studied wetlands, terms such as "swamp", "marsh", or ‘bog’ probably mean

something to you. Despite the advantages of familiarity, common terms have their drawbacks.

Often these terms are highly localized - for example, what is called a "heath" in New

Hampshire or Maine might be referred to as a "spong" in New Jersey (Johnson, 1985). Even

fairly universal terms such as "bog" can prove problematic. In some areas "bog" can refer to

any peat accumulating wetland while in other places it might refer to a specific type of moss-

lichen wetland. Most people use these terms interchangeably to many who study wetlands these

terms have specific meanings which richly describe the various wetland environments they

represent. However, before discussing the meaning of these traditional terms, we should look

first at some general definitions of wetlands.

One of the earliest of the currently important definitions, often referred to as the

Circular 39 definition, was developed by the U. S. Fish and Wildlife Service as part of a

wetland classification system for categorizing waterfowl habitat. This classification is still used

to differentiate between various wetland types for wildlife habitat purposes.

The term "wetlands "... refers to lowlands covered with shallow and sometimes temporary or

intermittent waters. They are referred to by such names as marshes, swamps, bogs, wet

meadows, potholes, sloughs, fens and river overflow lands. Shallow lakes and ponds, usually

with emergent vegetation as a conspicuous feature, are included in the definition, but the

permanent waters of streams, reservoirs, and portions of lakes too deep for emergent

vegetation are not included. Neither are water areas that are so temporary as to have little or

no effect on the development of moist-soil vegetation.

----------Wetlands of the United States, Their Extent and Their Value for Waterfowl and Other Wildlife (Shaw and

Fredine, 1956).

There are many others definitions, however, The Cowardin definition is one of the most

comprehensive and ecologically oriented definitions of wetlands and was developed by the U.

S. Fish and Wildlife Service as part of a wetlands inventory and classification effort...

Wetlands are lands transitional between terrestrial and aquatic systems where the water table

is usually at or near the surface or the land is covered by shallow water... wetlands must have

one or more of the following three attributes: (1) at least periodically, the land supports

predominantly hydrophytes; (2) the substrate is predominantly undrained hydric soil; and (3)

the substrate is nonsoil and is saturated with water or covered by shallow water at some time

during, the growing season of each year.

----------Classification of Wetlands and Deepwater Habitats of the United States (Cowardin et al., 1979).

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These definitions are descriptions of the physical attributes of wetlands and are used chiefly to

identify wetlands for regulatory purposes, but wetlands are more than physical places where

water is present and certain plants grow. Wetlands perform a variety of unique physical,

chemical and biological functions which are essential to the health of the environment and

valuable to society, but which are also difficult to define or identify for regulatory purposes.

Wetlands exist between aquatic and terrestrial ecosystems and are, therefore, influenced by

both. Wetlands are lands where water is present on the soil surface or within the root zone of

plants, usually within about 18 inches of the soil surface. Because of the presence of water,

wetlands have soil properties which differ from upland areas. Only hydrophytes, plants that are

adapted to an environment where water is present in the root zone either permanently or for

extended periods of time, can survive in such soils. The type of soil, the amount of organic

matter, the depth to which the water table will rise, the climate, and the season and duration of

high water will determine the kinds of plants that will grow in a wetland. Therefore, wetland

types are identified, in part, by the kinds of plants that grow in them and the degree of surface

flooding or the degree of soil saturation due to a high water table. Any of these definitions may

suffice for the purposes of protection and enhancement of wetland functions. However, for

regulatory purposes, it is important to know that there are several similar definitions in

common use, but the one that currently applies for the regulatory purposes of the Clean Water

Act is the 1987 Corps of Engineers definition.

The term "wetlands" means those areas that are inundated or saturated by surface or ground

water 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.

Corps of Engineers Wetlands Delineation Manual (U.S. Army Corps of Engineers 1987)

It is easier to avoid negative impacts on wetlands if the land in question is recognized as

wetland at the beginning of the planning process. Identifying wetlands when the land is

inundated or flooded with water is not difficult, but wetlands are not always inundated and

many wetlands are never inundated.

Therefore, it is necessary to be able to identify wetlands by other means. While

identification and delineation of wetlands under the Clean Water Act is a complex process

involving soils, plant communities and hydrology, there are a number of easily recognized

signs that can be used as indicators that the area may be a wetland.

Wetland Characteristics

Water presence of water at or near the ground surface for a part of the year.

Hydrophytic Plants a preponderance of plants adapted to wet conditions.

Hydric Soils soil developed under wet conditions.

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Wetlands can be simply classified into three broad categories of wetland types, based on the

growth form of plants: (1) marshes, where mostly non-woody plants such as grasses, sedges,

rushes, and bulrushes grow; (2) shrub wetlands, where low growing, multi-stemmed woody

plants such as swamp azalea, high bush blueberry and sweet pepperbush occur; and (3) forested

wetlands, often called swamps or wooded wetlands, where trees are the dominant plants.

Types of Wetlands

• MARSHES - Reeds, rushes, grasses and sedges growing in shallow water along the edge of

lakes and rivers.

• FRESHWATER SWAMP FOREST - herb species forests, growing on saturated or flooded

soils, normally in a zone along the lower reaches of rivers.

• PEATLAND - spongy waterlogged land formed as a result of slow decomposition of plant

materials.

• FLOODPLAIN - flat land or low land bordering rivers that are subject to periodic flooding.

• MANGROVE - wood trees growing along muddy estuaries of large rivers and sheltered

coastal areas.

• LAKES - standing bodies of water occupying large basins or small depressions.

• ESTUARINE, MARINE AND COASTAL ZONE WETLANDS - Estuaries are the contact

areas between freshwater and marine environments. Marine zone wetlands consist of

permanent shallow water habitats less than six metres deep at low tide.

• MAN-MADE WETLANDS - such as fish and shrimp ponds, paddy fields, reservoirs, ex-

mining lakes, gravel pits and sewerage farms and canals.

Wetlands in India

India has a wide variety of inland and coastal wetland habitats. Look around in your own

neighbourhood, and you are sure to spot a wetland or two - a lake or maybe a small pond!

The total area of wetlands (excluding rivers) in India is about 18.4% of the country, 70% of

which comprises areas under paddy cultivation.

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There are 8 different categories of wetlands in India, differentiated by region:

• The reservoirs of the Deccan Plateau in the south, together with the lagoons and the other

wetlands of the southern west coast;

• The vast saline expanses of Rajasthan, Gujarat and the gulf of Kachchh ;

• Freshwater lakes and reservoirs from Gujarat eastwards through Rajasthan (Kaeoladeo Ghana

National park) and Madhya Pradesh;

• The delta wetlands and lagoons of India 's east coast (Chilka Lake); the freshwater marshes

of the Gangetic Plain;

• The floodplain of the Brahmaputra ;

• The marshes and swamps in the hills of north-east India and the Himalayan foothills;

• The lakes and rivers of the montane region of Kashmir and Ladakh;

• The mangroves and other wetlands of the island arcs of the Andamans and Nicobars.

HYDROLOGY

Hydrology, the way in which a wetland is supplied with water, is one of the most important

factors in determining the way in which a wetland will function, what plants and animals will

occur within it, and how the wetland should be managed. Since wetlands occur in a transition

zone where water based ecosystems gradually change to land based ecosystems, a small

difference in the amount, timing or duration of the water supply can result in a profound change

in the nature of the wetland and its unique plants, animals and processes.

In headwater areas where streams originate, watersheds tend to be small and have

shallow soils with low water storage capacity. Hydroperiods of wetlands in headwater areas

often show water levels that rise and fall rapidly in response to localized storm events which

supply the streams and wetlands with runoff. An exception is areas where soils are dominated

by sandy glacial deposits. These areas tend to have deeper soils, gentle slopes and more

predictable hydroperiods. Sandy glacial deposits also tend to occur in colder climates and to be

frozen for a period of the year often providing the opportunity to conduct management

predictable hydroperiods. Sandy glacial deposits also tend to occur in colder climates and to be

frozen for a period of the year often providing the frozen conditions.

Larger streams, which receive much of their water from the combined flows of many

smaller streams, tend to respond more slowly to precipitation and exhibit the results of the

average conditions over the larger combined watershed as opposed to local storm events.

Hydroperiods of wooded swamps

associated with larger river systems tend to

show water levels that reflect events

general to the larger area such as fall rains

and spring thaw and are, therefore, more

predictable.

The number of times that a wetland is

flooded within a specific time period, such

as yearly, is known as the flood frequency.

Flood duration is the amount of time that

the wetland is actually covered with water.

It should also be noted that many wetlands

are never flooded, but the wetland

definition does require the soil to be saturated for at least a part of the growing season. Only

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hydrophytes, a relatively small group of vascular plants with special adaptations which,

includes many endangered species, are able to survive in soils that are saturated for more than a

short period during the growing season. Therefore, the duration and timing of flooding and or

saturation will limit the number of species that can survive in the wetland.

Residence time is a measure of the time it takes a given amount of water to move into,

through and out of the wetland. Since chemical processes take time and follow one another

sequentially, the degree to which wetlands can change water chemistry is determined to an

extent by residence time. This is one reason why it is important not to create a channel across a

wetland in the direction of flow, increasing outflow rate and decreasing residence time.

Wetlands receiving inflow from groundwater are known as discharging wetlands

because water flows or discharges from the groundwater to the wetland. A recharge wetland

refers to the reverse case where water flows from the wetland to the groundwater. Recharge and

discharge are determined by the elevation of the water level in the wetland with respect to the

water table in the surrounding area. Riparian wetlands often have both functions, they are

discharge wetlands, receiving groundwater inflow from upslope areas and they are recharge

wetlands in that they feed lower elevation groundwater through groundwater outflow. The

same wetland may be a discharging wetland in a season of high flow and a recharging wetland

in a dry season. Seeps at the base of mountains are often discharging wetlands formed by

groundwater breaking through to the surface of the ground at the base of steep slopes. Vernal

ponds often occur in these areas, but are an exception in that groundwater flow to and from

vernal ponds is practically nil in the northeast. Mountain top swamps are often wetlands

recharging with groundwater out-flows to a water table much lower in elevation.

Inflow water reaches the wetland from precipitation, surface flow, subsurface flow and

groundwater flow. Surface flow includes surface runoff, stream-flow and flood waters. Flood

waters can carry nutrient laden sediments to forested floodplains where these sediments are

deposited making the soil very fertile. Forested floodplains can be very productive.

Outflow leaves the wetland by evaporation, transpiration, surface flow, subsurface flow or

groundwater flow. Evaporation is water given off to the atmosphere as water vapor.

Transpiration is the process whereby water taken up by plant roots is released as vapor to the

atmosphere from the plant leaves. Surface flows out of wetlands can be small or large and are

often the origin point of streams. Wetlands are often connected, to a degree, with surface and

groundwater outflows of one wetland supplying the inflows to other wetlands lower in the

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watershed. The water supply to the lower wetland can be delayed until the upper wetland fills

to a point where additional water runs off. As a result, some wetlands will not be as well

supplied as others in dry periods.

As stated previously, the water storage capacity of the wetland is affected by the soil, the

groundwater level and the surface contour. Wetlands generally occur in natural depressions in

the landscape where geologic or soil layers restrict drainage. The surface contours act to collect

precipitation and runoff water and feed it to the depressed area. Groundwater recharge can take

place if the soil is not already saturated and the surface contours of the basin hold the water in

place long enough for it to percolate into the soil. In many cases the shape of the basin is such

that it can be rapidly filled by precipitation or flood waters and the water slowly released by a

restricted surface outlet, by slowly permeable soil or by geologic

conditions.

The water storage capacity of the wetland determines the volume and

timing of water reaching the stream from precipitation. The precipitation

reaches the stream in the form of groundwater or surface runoff to

contribute to stream flow discharge. A hydrograph is a graph of the

volume and timing of stream flow discharge measured at a certain point

in the watershed. The hydrograph shows the lapse time, the amount of

time between the onset of precipitation and the peak storm flow

discharge. It also depicts the volume and distribution of the storm flow

discharge over time. Wetlands tend to have longer response times and

lower peak storm flows distributed over longer time periods. Urban and

developed lands tend to have short response times and high volume,

short duration storm flow discharges. The overall effect is that

watersheds with wetlands tend to store and distribute storm flows over

longer time periods resulting in lower levels of stream flow and reduced

probability of flooding.

SOILS

One of the identifying characteristics of wetlands, from both ecological and statutory points of

view, is the presence of hydric, or wet, soils. Hydric soils are defined by the U.S.D.A. Natural

Resources Conservation Service (NRCS) as "soils that formed under conditions of saturation,

flooding or ponding long enough during the growing season to develop anaerobic conditions in

the upper part".

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The three critical

factors that must exist

for the soil to be

classified as hydric

soil are saturation,

reduction and

redoximorphic

features. When a

dominant portion of

the soil exhibits these

three elements the soil

is classified a hydric

soil.

Saturation, the first

factor, occurs when

enough water is

present to limit the

diffusion of air into

the soil. When the soil is saturated for extended periods of time a layer of decomposing organic

matter accumulates at the soil surface.

Reduction, the second factor, occurs when the soil is virtually free of elemental oxygen.

Under these conditions soil microbes must substitute oxygen containing iron compounds in

their respiratory process or cease their decomposition of organic matter.

Redoximorphic features, the third

factor, include gray layers and gray

mottles both of which occur when

soil microbes in anaerobic soils

reduce iron compounds. Iron, in its

reduced form, is mobile and can be

carried in the groundwater solution.

When the iron and its brown color

are thus removed, the soils show the

gray color of their sand particles.

The anaerobic, reduced zones can be

recognized by their gray, blue, or

blue-gray color. The mobilized iron

tends to collect in aerobic zones

within the soil where it oxidizes, or

combines with additional oxygen, to

form splotches of bright red orange color called mottles. The mottles are most prevalent in the

zones of fluctuating water and thus help mark the seasonal high water table.

The blue-gray layer with mottling generally describes wetland mineral soils. However,

where saturation is prolonged, the slowed decomposition rate results in the formation of a dark

organic layer over the top of the blue-gray mineral layer. Although classification criteria are

somewhat complex, soils with less than 20 percent organic matter are generally classified as

mineral soils and soils with more than 20 percent organic matter are classified as organic soils.

For the purposes of this document, the organic layer becomes important when it reaches a

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thickness of approximately 16 inches. Under the right conditions, the layer can grow to many

feet in thickness.

The organic soils are separated in the soil survey into Fibrists,

Saprists, and Hemists. The Fibrists, or peat soils, consist of soils in

which the layer is brown to black color with most of the

decomposing plant material still recognizable. In Saprists, or muck

soils, the layer is black colored and the plant materials are

decomposed beyond recognition. The mucks are black and greasy

when moist and almost liquid when wet. Mucks have few

discernible fibers when rubbed between the fingers and will stain

the hands. The Hemists, mucky peats, are in between in both color

and degree of decomposition.

The amount and decomposition of the organic component

determines several important differences between mineral and

organic wetland soils.

Organic soils have lower bulk densities that are lower weight

per unit of volume, than mineral soils. Consequently, organic soils

have more pore space and greater water holding capacity and while

flooded can be more than 80 percent water by volume. By contrast,

minerals soils are usually less than 55 percent water. However,

water holding capacity has little effect on flood storage because the pores are usually filled and

do not readily release moisture from the less porous lower layers.

The hydraulic conductivity, a measure of the speed at which water can move through the

soil, varies considerably both within and between organic and mineral soils. While organic

soils may have a larger water storage capacity, water movement may be considerably slower

than in mineral soils. Much depends on the degree of decomposition of organic matter.

However, the effect tends to extend the response time or period of time between the onset of a

storm event and the resulting peak stream flow as discussed in the hydrology section.

Decomposition is also important

in determining the location of

the levels of greatest flow with

respect to the surface in organic

soils. The chart shows that more

than 90 percent of the horizontal

water flow in organic soil

wetlands occurs at a depth of

less than twelve inches below

the surface.

Relatively undecomposed

organic matter near the surface

creates larger pore spaces

permitting greater flows. As

depth increases and organic

matter is more completely

decomposed, pore spaces are blocked by ever finer particles of organic matter and flow is

reduced.

Organic soils tend to be richer than mineral soils in the nutrients important to plant

productivity. But organic soils often have very low productivity because the nutrients present

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are bound in organic compounds and thus unavailable for plant growth. Therefore, unless the

wetland receives an inflow of nutrients from other sources, the plant forms present are apt to be

those with low nutrient requirements or special adaptations such as carnivorous plants.

When not flooded, organic soils generally have more hydrogen cations available,

tending to make them more acid than mineral soils. Hence, acid loving plants are associated

with organic soils. An example is the sphagnum mat or ring that forms around a bog lake.

Exceptions are those fens which are influenced by limestone geology and thus receive calcium

bicarbonate in groundwater. The bicarbonate easily removes the free hydrogen cations by

forming water and carbon dioxide and results in fens that are neutral to basic.

Organic soils have a greater potential for removal of excess nutrients and other

pollutants. Small soil particles with large surface to volume ratios have the ability to attract and

hold positively charged ions, known as cations such as ammonium (NH4+) and calcium (CA

2+).

The cations are adsorbed or loosely held by electrical attraction. Cations held in this way may

be stored for extended periods in sediments or removed and incorporated into other natural

compounds by chemical or microbial activity. When the adsorbed cations are incorporated into

other compounds the soil particles become available to adsorb additional cations. In this way,

wetland soils maintain their ability to remove and recycle excess nutrients and other pollutants.

Cation exchange capacity is one measure of the potential for wetland soils to alter the

chemistry of the waters moving through them and to transform nutrients into other forms.

VEGETATION

Another physical characteristics used to identify wetlands is the presence of hydrophytic

vegetation. The term hydrophyte comes from the Greek words hydro, meaning water, and

phyton, meaning plant. The term hydrophyte includes all aquatic and wetland plants. However,

the term is generally used to refer to vascular aquatic and wetland plants. Though hydrophytes

represent only a small percentage of the total plant population, there are far too many to list

here.

Upland plants normally have adequate soil oxygen available to the roots for use in the

metabolic processes that convert food into energy. When soil saturation or flooding make

oxygen unavailable, the metabolic process either stops altogether or shifts to anaerobic

glycolysis, an enzymatic process that does not require oxygen to convert food into energy.

Anaerobic glycosis produces much less energy than normal metabolic processes and causes an

accumulation of toxic end products. Using anaerobic glycosis, most plants can produce only

enough food to survive for short periods of time. Hydrophytic plants thrive in wetland soils in

spite of the limitation or absence of oxygen because they are able to make special physiological

adaptations.

Hydrophytic plants vary in the number of adaptations they exhibit, but generally

those that exhibit a greater number of adaptations also exhibit greater tolerance to saturated soil

conditions. Relatively few tree species, such as cypress and water tupelo, are able to make

enough of these adaptations to tolerate flooding for more than a few weeks during the growing

season. However, there are a number of species that exhibit one or more of these adaptations

and thus tolerate varying degrees of soils wetness.

Some plants such as green ash form hypertrophied lenticels, enlarged structures on the

above ground portion of the plant that permit the exchange of gasses with the atmosphere

facilitating the transfer of oxygen from the air to the plant tissue. Green ash and northern white

cedar grow large diameter, succulent roots at least partially composed of cells with air spaces

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between them, called aerenchyma, which facilitate movement of oxygen throughout the root

tissue. Water hickory, black spruce and balsam fir develop fibrous, lateral root systems which

tend to spread horizontally above the wetter soil levels. Larch, water hickory and water tupelo

develop adventitious roots, extra roots on the tree stem, again, above the level of the wetter soil.

Bald cypress and water tupelo develop a swelling at the base of the tree which helps resist wind

throw and may facilitate the exchange of oxygen.

In some wetland adapted plants such as cordgrass, Spartina, the oxygen supply is large

enough to cause oxygen to be diffused out through the roots oxygenating the rhizosphere, or

outer surface of the root. Soil iron and manganese deposits in these areas are often oxidized by

this method resulting in streaks of rust commonly seen in wetland soils.

BIOGEOCHEMICAL CYCLES

The basic elements that occur in living organisms move through the environment in a series of

naturally occurring physical, chemical and biological processes known as biogeochemical

cycles. The cycle generally describes the physical state, chemical form, and biogeochemical

processes affecting the substance at each point in the cycle in an undisturbed ecosystem. Many

of these processes are influenced by microbial populations that are naturally adapted to life in

either aerobic, oxygenated, or anaerobic, oxygen free, conditions. Because both of these

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conditions are readily created by varied and fluctuating water levels, wetlands support a greater

variety of these processes than other ecosystems.

There is usually a physical state, chemical

form, and location in the cycle in which nature

stores the bulk of the various chemical

elements. Pollution occurs when the cycle is

sufficiently disturbed that an element is caused

to accumulate at some point in the cycle in an

inappropriate physical state, chemical form,

location or amount disrupting environmental

balance.

In the nitrogen cycle, for example, the bulk nitrogen is stored as nitrogen gas in the atmosphere.

The nitrogen cycling process in wetlands involves both aerobic and anaerobic conditions.

Nitrogen in the form of ammonium (NH4) is released from decaying plant and animal matter

under both aerobic and anaerobic conditions in a process known as ammonification. The

ammonium then moves to the aerobic layer where it is converted to nitrate (NO3). Nitrate not

taken up by plants or immobilized by adsorption onto soil particles can leach downward with

percolating water to reach the groundwater supply or move with surface and subsurface flow.

Nitrate can also move back to the anaerobic layer where it may be converted to nitrogen gas by

denitrification, a bacterial process, and subsequently returned to the atmosphere.

If both aerobic and anaerobic conditions were not available, some of the cycle

processes would cease and pollutants could accumulate. In wetlands, anaerobic conditions are

amply provided by flooding and by

saturated soils. However, the

oxygen requiring processes take

place in a thin oxidized zone

usually existing at the soil surface.

This layer may be only a fraction of

an inch thick and is present even

when the wetland is submerged. In

many wetlands the water table

fluctuates 12 to 18 inches each year

with the summer level averaging

between 4 and 18 inches below the

surface of the soil. This zone of

aeration is often called the active

layer or in Russian soil terminology, where it was first used, the acrotelm.

Phosphorus, sulfur, iron, manganese and carbon also move through the wetland

ecosystem in complex cycles. Sulfur and carbon, like nitrogen, have gaseous cycles. As a result

of the biogeochemical cycle processes, sulfides and methane are released into the atmosphere

attended by the smell of rotten eggs and swamp gas respectively. Phosphorus, however, has a

sediment cycle with excess phosphorus being tied up in sediments, peat in organic wetlands

and clay particles in mineral wetlands. However, although phosphorus retention is an important

attribute of wetlands, sediment attached phosphorus is subject to resuspension and movement

with water when sediments are disturbed.

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The cycles are similar in that they provide storage for excess elements and require a

certain amount of time to complete the chemical processes. The cycle processes also require the

varying environments provided by aerobic and anaerobic conditions. In closed systems, the

processes take place within the wetland. In open systems, like riparian wetlands, many

elements can be imported from or exported to adjacent systems with surface and groundwater

flows or flooding.

To avoid changing the natural biogeochemical function, it is important that the

hydrology of the wetland, the inflow, outflow and residence time of the water, remain relatively

undisturbed. It is also necessary to minimize disturbance to the aerobic zone of saturated soils.

However, even with minimal disturbance, wetlands will continue to function as net receptors

(sinks) or net exporters (sources) of various elements primarily due to seasonal and other

natural fluctuations in the biogeochemical cycle processes.

WETLANDS BEST MANAGEMENT PRACTICES

Three Primary Considerations

1. Consider the relative importance of wetland in relation to the total property to be

managed. Perhaps the wetland should simply be left undisturbed.

2. Protect the environment. Don’t alter the hydrology of the wetland by:

a. restricting the inflow or outflow of surface, sub-surface or groundwater,

b. Reducing residence time of waters,

c. Changing the temperature regime.

3. Protect wildlife and fish habitat to the extent that knowledge permits and to a level

consistent with its value to society.

All kinds of management practices can be traced back to these three primary considerations.

Global Scenario of Wetlands

The earth, two-thirds of which is covered by water, looks like a blue planet-the planet of water-

from space (Clarke, 1994). The world's lakes and rivers are probably the planet's most

important freshwater resources. But the amount of fresh water covers only 2.53% of the earth's

water. On the earth's surface, fresh water is the habitat of a large number of species. These

aquatic organisms and the ecosystem in which they live represent a substantial sector of the

earth's biological diversity.

It is interesting to know that there are nearly 14 x 108 cubic km of water on the planet,

of which more than 97.5% is in the oceans, which covers 71% of the earth's surface. Wetlands

are estimated to occupy nearly 6.4% of the earth's surface. Of those wetlands, nearly 30% is

made up of bogs, 26% fens, 20% swamps, and 15% flood plains. Of the earth's fresh water,

69.6% is locked up in the continental ice, 30.1% in underground aquifers, and 0.26% in rivers

and lakes. In particular, lakes are found to occupy less than 0.007% of world's fresh water

(Clarke, 1994). The total number of animal species, reported from, is 89,461; out of which

17,853 belong to wetlands comprising 19.9% of the total number. About 50,000 ha area of

wetlands is degraded every year in Asia. It results in soil acidification, soil erosion, loss of soil

nutrients, change in hydrology, loss of flora and fauna and disruption of delicate ecosystem.

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Wetlands Loss and Degradation:

Wetlands are estimated to occupy around 8.6 million sq km (6.4 %) of the earth's

surface, out of which about 4.8 million sq km are found in the tropics and sub-tropics. This

estimation was compared with estimates in the 19th century and it was found that

approximately 50% of the world's wetlands have been lost in the past century alone. The major

activities responsible for wetlands loss are urbanization, drainage for agriculture, and water

system regulation (Shine & de Klemm, 1999). Development activities, like excavation, filling,

draining, and so forth, are the major destructive methods resulting in a significant loss of

wetland spatial spread throughout the country. Environmental impacts on wetlands may be

grouped into five main categories: loss of wetland area, changes to water regime, changes in

water quality, overexploitation of wetland products, and introduction of exotic or alien species.

These quality and quantity declinations, have contributed to the decline in the biological

diversity of flora and fauna, migratory birds, and productivity of wetland systems.

Simultaneously, several thousand species have become extinct, and fish, timber, medicinal

plants, water transport, and water supply are over exploited.

Indian Scenario of Wetlands

India is blessed with numerous rivers and streams. By virtue of its geography, varied

terrain, and climate, it supports a rich diversity of inland and coastal wetland habitats. Major

river systems in the north are Ganga, Yamuna, and Brahmaputra (perennial rivers from the

Himalayas) and in the south, Krishna, Godavari, and Cauvery (not perennial, as they are mainly

rain-fed). The central part of India has the Narmada and the Tapti. The Indo-Gangetic

floodplain is the largest wetland regime of India. Most of the natural wetlands of India are

connected with the river systems of the North and the South. The lofty Himalayan mountain

ranges in northern India accommodate several well-known lakes, especially the palaearctic

lakes of Ladakh and the Vale of Kashmir, which are sources of major rivers. In the northeastern

and eastern parts of the country are located the massive floodplains of Ganga and Brahmaputra

along with the productive system of swamps, marshes, and oxbow lakes. Apart from this, there

exist a number of man-made wetlands for various multipurpose projects. Examples are Harike

Barrage at the confluence of the Beas and the Sutlej in Punjab, Bhakra Nagal Dam in Punjab

and Himachal Pradesh, and the Cosi Barrage in Bihar-Nepal Border. India's climate ranges

from the cold, arid Ladakh to the warm, arid Rajasthan, and India has over 7,500 km of

coastline, major river systems, and mountains. There are 67,429 wetlands in India, covering

about 4.1 million hectares. Out of these, 2,175 wetlands are natural, covering about 1.5 million

hectares, and 65,254 wetlands are man-made, occupying about 2.6 million hectares. According

to Forest Survey of India, mangroves cover an additional 6,740 sq km. Their major

concentrations are Sunderbans, Andaman, and Nicobar Islands, which hold 80% of the

country's mangroves. The rest are in Orissa, Andhra Pradesh, Tamilnadu, Karnataka,

Maharashtra, Gujarat, and Goa.

Wetlands have been drained and transformed due to anthropogenic activities, like

unplanned urban and agricultural development, industries, road construction, impoundments,

resource extraction, and dredge disposal, causing substantial economic and ecological losses in

the long term. They occupy about 58.2 million hectares, of which 40.9 million hectares are

under paddy cultivation. About 3.6 million hectares are suitable for fish culture. Approximately

2.9 million hectares are under capture fisheries (brackish and freshwater). Mangroves,

estuaries, and backwaters occupy 0.4, 3.9, and 3.5 million hectares respectively. Man-made

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impoundments constitute 3 million hectares. Nearly 28,000 km are under rivers, including main

tributaries and canals. Canal and irrigation channels constitute another 113,000 km.

Though accurate results on wetland loss in India are not available, the Wildlife Institute

of India's survey reveals that 70-80% of individual fresh water marshes and lakes in the

Gangetic flood plains have been lost in the last five decades. Indian mangrove areas have

decreased by half from 700,000 ha in 1987 to 453,000 ha in 1995.

The wetlands of Assam, Bihar and West Bengal in the Ganga and Brahmputra basin

have shown high fish production potential (1000-2000 Kg/ha/yr). Many wetlands, specially the

live ox-bow lakes, with connecting channels with rivers and tectonic lakes (Chaurs of Bihar

and beels of Assam), are known to act as collection sink of riverine fish stock due to the ingress

of flood waters. Contrary to reservoirs with estimated average fish yield of 20 Kg/ha/yr

(Sugnan, 1995), floodplain lakes have indicated an average yield of more than 150 Kg/ha/yr

even in unmanaged state.

The floodplain lakes are generally neglected ecosystems. However, certain lakes are

partially managed, especially in the line of aquaculture. Fisheries management in wetlands is

more of ad-hoc type rather than based on any principled or scientific approach. In case of

partially managed wetlands, fishermen cooperative societies manage such lake on share basis.

It is generally believed that harvesting of fish from wetlands is renewed due to their

connections with river. But, this is not the case. Presently most of the water bodies have lost

this vital characteristic due to several reasons. The wetlands ecosystem remains no more

lucrative in terms of fish out-put for which following factors may be responsible.

• Hydrologic alterations, which include changes in the hydrologic structure and

functioning of a wetland by direct surface drainage, de-watering by consumptive use of

surface water inflows, unregulated draw down of unconfined aquifer from either

groundwater withdrawal or by stream channelization, river valley modification,

deforestation for various human activities thereby destruction of fisheries habitats.

• Increased sedimentation, nutrient, organic matter, metals, pathogen, and other water

pollutant loading from both storm water runoff (non-point source) and wastewater

discharges (point source), which lead to high degree of eutrophication affecting the fish

and fisheries adversely.

• Poor auto stocking of prized fish seeds together with irrational killing juveniles and

brood fish stock.

• Irrational and conflicting land use pattern in the catchments areas: This includes Change

in characteristic wetland flora and fauna (exotic), reclamation of marginal areas of

wetlands either for agriculture or for human settlements.

• Poor financial status of fishermen community, poor state of management, injudicious

application of nets and crafts.

• Lack of scientific innovations, poor understanding of ecological intricacies and

conservation methods.

Example: The overexploitation of wetlands in east Calcutta is evident, as it is used for

disposing untreated sewage, runoff from urban and agricultural areas, changed land use

within the watershed, and so forth. All these unplanned shortsighted anthropogenic

activities have resulted in rendering the ecosystem integrity in peril.

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Sustainable Fisheries Management strategies for wetlands:

1. Fishery must be conducted in a manner that does not lead to over-fishing, or for those stocks

that are over-fished, the fishery must be conducted such that there is a high degree of

probability the stock(s) will recover.

This can be achieved by fulfilling following aspects:

a. The fishery shall be conducted at catch levels that maintain ecologically viable stock

levels at an agreed point or range, with acceptable levels of probability.

b. Where the fished stock(s) are below a defined reference point, the fishery will be

managed to promote recovery to ecologically viable stock levels within nominated

timeframes.

2. Fishing operations should be managed to minimise their impact on the structure,

productivity, function and biological diversity of the wetland ecosystems.

This can be achieved by fulfilling following aspects:

a. The fishery is conducted in a manner that does not threaten by-catch species.

b. The fishery is conducted in a manner that avoids mortality of, or injuries to,

endangered, threatened or protected species and avoids or minimises impacts on

threatened ecological communities.

c. The fishery is conducted, in a manner that minimises the impact of fishing operations

on the wetland ecosystems.

3. Fishermen groups and cooperative Societies must be strengthened and be made accountable.

This can be achieved by fulfilling following aspects:

a. Strengthened the mechanism for transfer of scientific technology i.e. regular

environment education/awareness programmes, training and demonstration programmes

for fishermen community.

b. Strengthened the credit and subsidy schemes and like other crops fishery sector should

be brought under insurance scheme.

Eco-aquaculture and its scope in wetland management:

Like ecoagriculture in land, development of ecoaquaculture is a suggestive measure in

maintaining good health of the aquatic ecosystem for not only protecting the health of the

ecosystem but to sustain the farmers’ interest also in long run. For West Bengal, it is essential

considering the level of poverty of the farmers and their dependence on the wetlands.

Ecoaquaculture implies enhancing productivity of aquaculture systems as well as

scope of enhancing the income of the farmers through maintaining a sustainable ecosystem

with a safe limit of biodiversity. An experiment was done in the East Calcutta Wetlands, a

Ramsar site of India, during 2001 to 2003 to draw an important conclusion, whether it is

possible to enhance biodiversity of water bodies without disturbing the existing fishing practice

(Ghosh and Ghosh, 2003).

Experiment in the East Calcutta Wetlands

The East Calcutta Wetlands is not significant for its rich biodiversity. These cluster of wetlands

on the contrary, sustain a traditional knowledge system that brings out the best of human

ingenuity in using a number of functions. It has the world’s largest ensemble of wastewater

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ponds growing fish. Effluents of such ponds reach downstream paddy fields. All these practices

using wastewater cover an area of 12,500 ha.

The programme of enhancing the biodiversity stock of the East Calcutta Wetlands

deserves prominent attention. Interestingly, such an effort of enriching biodiversity stock is first

ever in these wetlands, although biologists have been studying the wetlands for quite sometime.

Local people were chosen as the mainstay of the work. The plantation of selected wetland

plants in the unused parts of the water bodies, training in traditional craft using wetland plants

and biodiversity awareness, all these three elements of the projects centered entirely on the

local people. However, with the completion of the project, no sustainable change was noticed

nor any tangible result shown that has grown any desirable local competence in enhancing the

biodiversity of the East Calcutta Wetlands, although the signs of potentiality amongst the local

people to adopt such skills and conservation practices were profoundly visible. What was

happened was the time frame designed by the funding agency was inappropriate. A one time

effort to make a dramatic change in the scenario is never possible and there is no such example

in the world. Continuity of such type of work was more important for a definite time scale to

achieve the goal. Interest of local farmers to involve in this type of work was definitely an

important achievement and their realisation regarding the need of enhancing diversity from

their traditional knowledge base.

Glossary of related terms

What is Ramsar Convention? What does it mean by Ramsar site?

February 2nd is celebrated as World Wetlands Day. It marks the date of the signing of the Convention

on Wetlands on 2 February 1971, in the Iranian city of Ramsar on the shores of the Caspian Sea. The

Convention on Wetlands, 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.

There are presently 150 Contracting Parties to the Convention, with 1591 wetland sites, totaling 134

million hectares, designated for inclusion in the Ramsar List of Wetlands of International Importance.

Mission Statement: "The Convention's mission is the conservation and wise use of all wetlands through

local, regional and national actions and international cooperation, as a contribution towards achieving

sustainable development throughout the world".

Oxbow lake:

A crescent-shaped lake (often temporary) that is formed when a

wide meander from a stream or river is cut off from the main

channel to form a lake.

A Horseshoe or oxbow lake at Arkansas (USA)

Formation:

When a river reaches a low-lying plain in its final course to the sea or a lake, it meanders widely. Deposition occurs on the convex bank because of the ‘slack water’, or water at low velocity. In contrast, both lateral erosion and undercutting occur on the concave bank where the stream’s velocity is the highest. Continuous erosion of a concave bank and deposition on the convex bank of a meandering river cause the formation of a very pronounced

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meander with two concave banks getting closer. The narrow neck of land between the two neighbouring concave banks is finally cut through by either lateral erosion of the two concave banks of the strong currents during a flood. When this happens, a new straighter river channel is created and an abandoned meander loop, called a cut-off, is formed. When deposition finally seals off the cut-off from the river channel, an oxbow lake is formed.

Floodplain:

A flood plain is a plain land formed along the course of a river by the deposition of sediment,

typically dropped by a river during periodic floods. Floodplains contain such features as levees

(river embankments built by deposition as the river floods), backswamps, delta plains, and

oxbow lakes. Rivers with extensive floodplains are the Nile, Ganges, Danube, and Po.

Floodplains are generally very fertile, thus making them rich agricultural lands. The

disadvantage of farming on a floodplain is the natural hazard of floods. In the United States

there has been extensive house construction on floodplains in recent years, necessitating the

construction of new dams to control small, annual floods. The flood plain may become a level

area of great fertility, similar in appearance to the floor of an old lake. The flood plain differs,

however, in as much as it is not altogether flat. It has a gentle slope down-stream, and often, for

a distance from the side towards the center.

Flood Plain along Lynches River Johnsonville, South Carolina Showing

high water mark on trees.

Delta:

A Greek letter sits at the mouth of many rivers. Noticing the resemblance between the island

formed by sediment at the mouth of a river such as the Nile and the triangular shape of their

letter delta (∆), the Greeks gave the name delta to such an island. English borrowed this sense

from Greek, although the word delta appeared first in English as the name of the letter, in a

work written possibly around 1200. The sense “alluvial deposit” is not recorded until 1555,

when delta is used with reference to the Nile River delta.

A deposit of clay, silt, and sand formed at the mouth of a river where the stream loses

velocity and drops part of its sediment load. No delta is formed if the coast is sinking or if there

is an ocean or tidal current strong enough to prevent sediment deposition. Coarse particles

settle first, with fine clays last and found at the outer regions of the delta. The three main

When the slope down which a river runs has become very slight, it is unable to carry the sediment brought from higher regions nearer its source, and consequently the lower portion of the river valley becomes filled with alluvial deposits. Since, in times of flood, the rush of water in the high regions tears off and carries down a greater quantity of sediment resulting in planation, with aggradation. That is, they may be due to a graded river working in meanders from side to side, widening its valley by this process and covering the widened valley with sediment. Or the stream -- by cutting into another stream (piracy), by cutting through a barrier near its head waters, by entering a region of looser or softer rock, and by glacial drainage -- may form a flood plain simply by filling up its valley (alluviation only). Any obstruction across a river's course, such as a band of hard rock, may form a flood plain behind it, and indeed anything that checks a river's course and causes it to drop its load will tend to form a flood plain. Still, flood plains are most commonly found near the mouth of a large river, such as the Rhine, the Nile, or the Mississippi, where there are occasional floods and the river usually carries a large amount of sediment. "Levees" are formed, inside which the river usually flows, gradually raising its bed above the surrounding plain. Occasional breaches during floods cause the overloaded stream to spread in a great lake over the surrounding country, where the silt covers the ground in consequence.

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varieties of deltas are the arcuate (the Nile), the bird's-foot (the Mississippi), and the cuspate

(the Tiber). The Nile, Mississippi, Niger, Rhine, Danube, Kuban, Volga, Amu Darya, Indus,

Ganges-Brahmaputra, Ayeyarwady, Tigris and Euphrates, and Huang He (Yellow) rivers are

among those that have formed large deltas, many of which are fertile lands that support dense

agricultural populations.

Photo of Nile delta from space Farming in the Nile Delta

Creek:

A small stream of water which serves as the natural drainage course for a drainage basin of

nominal or small size. The term is a relative one as to size, some creeks in the humid section

would be called rivers if they occurred in the arid portion.

Backswamps:

Seasonal backswamps are small water bodies that

may or may not dry out in any single year. They

are located in depressions close to the raised levee

banks of Mekong tributaries such as the Sedone.

Hydrologically, the ecological significance of

backswamps is to take up some of the flood during

the wet season peaks. Because they are located in

depressions close to the river, backswamps are

flooded more regularly than, and prior to, the rest

of the floodplain. Backswamps form a major

habitat for a number of fish species, notably catfish

and snakeheads. They also probably serve as a

spawning ground for migratory species that spend

other parts of their life cycle in flowing waters. The

main ecological threats to backswamps include

local pump irrigation schemes that dry out the

swamps, and in some cases fishing practices that

utilise diesel pumps to drain the swamp. Increasing

use of pesticides by rice farmers is also likely to

affect swamp ecology.

Backswamp, Loungtom

Mediterranean Sea

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Sources of literatures:

1. Ramachandra, T.V. (2001). Restoration and management strategies of wetlands in

developing countries. In Electronic Green Journal. Issue 15, Dec 2001.

http://egj.lib/uidaho.edu/egj15/

2. Kulshrestha, S.K. (2005). Biodiversity conservation of freshwater ecosystem in India.

In EnviroNews Archives. Vol. 11(4) April 2005News letter of ISEB, Lucknow, India.

www.geocities.com/isebindia/

3. Subir K. Ghosh (2005). Ecoaquaculture may be a novel concept in wetland

management. In Ecoaqua, 2006.

http://www.iucn.org/themes/cem/documents/newsletters/2006/docs/volume01/ ecoaqua-

2006pdf./ p.1-6.

4. V.V. Sugunan. Intregated development of floodplain wetland in India. In Utilising

different aquatic resources for livelihood in Asia: lake and reservoir based ecosystems.

www.iirr.org/aquatic_resources. p.28.

5. Ralph W Tiner (in U.S. Fish and Wildlife Service). Technical aspects of wetlands:

Wetlands definition and classification in the United States. United States Geological

Survey water supply paper 2425. In National Water Summary on Wetland Resources.

http://water.usgs.gov/nwsum/WSP2425/

6. http://www.iucn.org/themes/cem/documents/newsletters/2006/iucn_ecosystems1_arabic

_2006.pdf

7. Cefas. Sustainable fisheries management. www.cefas.co.uk/publications/marketting/

fisheries

8. Sinha, M., Khan, M.A. and Jha, B.C. (Eds.) (1999). Ecology, Fisheries and Fish Stock

assessment in Indian Rivers. CIFRI Bulletin No. 90. 306p.

9. Guidelines for ecologically sustainable management of fisheries p. 1-7.

http://www.deh.gov.auf/coasts/fiasheries/pubs/guidelines.pdf

10. http://www.ramsar.org/

11. http://www.birdlife.org/

12. http:www.nmfs.noaa.gov/habitat/

13. http://aswm.org/wetlands

14. http://epa.gov/owow/wetlands/

15. http://pasture.ecn.purdue.edu/AGEN521/epadir/wetlands/classifications 15. http://www.na.fs.fed.us/spfo/pubs/n_resource/wetlands/

16. http://www.charttiff.com/pub/WetlandMaps/Cowardin.pdf