627
The rise in the sea level, for example, both
increases and decreases the wetland’s spatial
extent depending on local factors.
Wetlands are under increasing stress due to the
rapidly growing population, technological development, urbanisation and economic growth.
Additional pressures on wetlands from natural
causes like subsidence, drought, hurricanes and
erosion and human threats coming from overexploitation, encroachment, reclamation of vast
wetland areas for agriculture, commercial and residential development and silviculture have altered
the rate and nature of wetland functions particularly in the last few decades. The primary pollutants causing degradation are sediments, nutrients,
pesticides, salinity, heavy metals, weeds, low dissolved oxygen, pH and selenium.
Wetland loss may be defi ned as ‘the loss of
wetland area, due to conversion of wetland to
non-wetland areas as a result of human activity’,
and wetland degradation is ‘the impairment of
wetland functions as a result of human activity’.
About 50 % of the world’s wetlands have been
lost in the last century, primarily through
drainage for agriculture, urban development and
water system regulations. It has been estimated
that nearly 1 ha of the world’s wetlands is getting degraded at the tick of every minute of the
clock.
Wetlands have been degraded and lost in ways
that are not as obvious as direct physical destruction or degradation. Other threats include chemical
contamination, excess nutrients and sediment from
air and water. On a global scale, climate change
could also affect wetlands through increased air
temperature; shifts in precipitation; increased frequency of storms, droughts and fl oods; increased
atmospheric carbon dioxide concentration; and sea
level rise. The loss of wetlands could be mainly
attributed to natural and anthropogenic activities.
Apart from pollution, the other major problems include hydrologic manipulations of wetlands in the form of fl ow alterations and
diversions, disposal of dredged or fi ll material,
sewage infl ows and construction of levees or
dykes leading to alterations in: (a) water currents,
erosion or sedimentation patterns, (b) natural
water temperature variations; (c) chemical,
nutrient and dissolved oxygen regime of the
wetland; (d) normal movement of aquatic fauna;
(e) pH of the wetland; and (f) normal water levels
or elevations.
All these impacts affect the wetland quality
and species composition and functions.
Some activities do, however, create wetlands.
Construction of farm ponds and, in some cases,
reservoirs and irrigation projects may increase
wetland spatial extent, although valuable natural
wetlands may be destroyed in the process.
Wetlands near urban centres are under increasing
developmental pressure for residential, industrial
and commercial facilities. Increasing population
and economic growth create high demand for real
estate in suburban localities. As suitable upland
becomes exhausted, pressure intensifi es to develop
wetlands for residential housing, manufacturing
plants, business offi ce complexes and similar uses.
They are often the fi nal refuge for wildlife in an
increasing urban environment and support many
upland animals displaced by development. With
accelerating development of adjacent uplands, the
role of urban wetlands in fl ood protection and
water quality maintenance becomes critical. Urban
and industrial development increases the amount of
surface water run-off from the land after rainfall.
This raises fl ood heights and increases the fl ow rate
of rivers, increasing the risks of fl ood damage.
Increased run-off brings with it various substances
that degrade water quality, such as fertiliser chemicals, grease and oil, road silt and sediment. Effl uents
from some sewage treatment plants built to handle
the needs of growing communities also reduce
water quality. And wetlands do the cleansing action
and remove many pollutants. Urban wetlands in
certain instances function as recharge areas. This is
especially true in communities where groundwater
withdrawals are heavy. Thus, urban wetlands are
essential for preserving public water supplies.
29.2.4.4 Wetlands as Dumping
Grounds
In some places, there is uncivilised use of the wetlands in the form of rendering them as dumping
grounds, thus leading to their dereliction. This is a
damage caused to the nature and a colossal loss
caused to the country.
29.2 Problems
The rise in the sea level, for example, both
increases and decreases the wetland’s spatial
extent depending on local factors.
Wetlands are under increasing stress due to the
rapidly growing population, technological development, urbanisation and economic growth.
Additional pressures on wetlands from natural
causes like subsidence, drought, hurricanes and
erosion and human threats coming from overexploitation, encroachment, reclamation of vast
wetland areas for agriculture, commercial and residential development and silviculture have altered
the rate and nature of wetland functions particularly in the last few decades. The primary pollutants causing degradation are sediments, nutrients,
pesticides, salinity, heavy metals, weeds, low dissolved oxygen, pH and selenium.
Wetland loss may be defi ned as ‘the loss of
wetland area, due to conversion of wetland to
non-wetland areas as a result of human activity’,
and wetland degradation is ‘the impairment of
wetland functions as a result of human activity’.
About 50 % of the world’s wetlands have been
lost in the last century, primarily through
drainage for agriculture, urban development and
water system regulations. It has been estimated
that nearly 1 ha of the world’s wetlands is getting degraded at the tick of every minute of the
clock.
Wetlands have been degraded and lost in ways
that are not as obvious as direct physical destruction or degradation. Other threats include chemical
contamination, excess nutrients and sediment from
air and water. On a global scale, climate change
could also affect wetlands through increased air
temperature; shifts in precipitation; increased frequency of storms, droughts and fl oods; increased
atmospheric carbon dioxide concentration; and sea
level rise. The loss of wetlands could be mainly
attributed to natural and anthropogenic activities.
Apart from pollution, the other major problems include hydrologic manipulations of wetlands in the form of fl ow alterations and
diversions, disposal of dredged or fi ll material,
sewage infl ows and construction of levees or
dykes leading to alterations in: (a) water currents,
erosion or sedimentation patterns, (b) natural
water temperature variations; (c) chemical,
nutrient and dissolved oxygen regime of the
wetland; (d) normal movement of aquatic fauna;
(e) pH of the wetland; and (f) normal water levels
or elevations.
All these impacts affect the wetland quality
and species composition and functions.
Some activities do, however, create wetlands.
Construction of farm ponds and, in some cases,
reservoirs and irrigation projects may increase
wetland spatial extent, although valuable natural
wetlands may be destroyed in the process.
Wetlands near urban centres are under increasing
developmental pressure for residential, industrial
and commercial facilities. Increasing population
and economic growth create high demand for real
estate in suburban localities. As suitable upland
becomes exhausted, pressure intensifi es to develop
wetlands for residential housing, manufacturing
plants, business offi ce complexes and similar uses.
They are often the fi nal refuge for wildlife in an
increasing urban environment and support many
upland animals displaced by development. With
accelerating development of adjacent uplands, the
role of urban wetlands in fl ood protection and
water quality maintenance becomes critical. Urban
and industrial development increases the amount of
surface water run-off from the land after rainfall.
This raises fl ood heights and increases the fl ow rate
of rivers, increasing the risks of fl ood damage.
Increased run-off brings with it various substances
that degrade water quality, such as fertiliser chemicals, grease and oil, road silt and sediment. Effl uents
from some sewage treatment plants built to handle
the needs of growing communities also reduce
water quality. And wetlands do the cleansing action
and remove many pollutants. Urban wetlands in
certain instances function as recharge areas. This is
especially true in communities where groundwater
withdrawals are heavy. Thus, urban wetlands are
essential for preserving public water supplies.
29.2.4.4 Wetlands as Dumping
Grounds
In some places, there is uncivilised use of the wetlands in the form of rendering them as dumping
grounds, thus leading to their dereliction. This is a
damage caused to the nature and a colossal loss
caused to the country.
29.2 Problems