286
Typha spp., which is a cosmopolitan wetland
plant, is called ‘cattail’ in America, ‘reed mace’
in the UK, ‘cumbungi’ in Australia, and ‘raupo’
and ‘bulrush’ in New Zealand. However, true bulrush is still called Scirpus spp. in North America.
It is believed that the European terminology is
older and richer. It distinguishes at least four
different kinds of freshwater wetlands, namely ,
(a) mineral-rich reed beds called reed swamps,
(b) wet grassland marshes, (c) fens and (d) bogs
or moors. According to some (e.g. Moore 1984 ),
all these wetland types are considered as ‘mires’.
It may be noted here that the European classifi cation is based on the amount of surface water
and nutrient fl ow (rheotrophy), type of vegetation, pH and peat-building characteristics.
On the other hand, as briefl y indicated above,
the classifi cation of wetlands in the Indian subcontinent and Bangladesh is based on certain
defi nite and simple observable criteria of retention of water in the wetlands. However, the three
local terms mentioned above may have other synonyms in different languages; but, the overall
basis of classifi cation based on retention of water
in the wetland generally remains the same.
On the basis of the above discussion, two
points could be emphasised regarding the use of
common terms in classifying wetland types:
(a) The physical and biotic characteristics grade
continuously from one of the wetland types
to the next. Hence, any classifi cation based
on common terms is, to some extent, arbitrary and may be avoided, if possible.
(b) The same term may refer to different systems
in different regions. The common terms seem
to be in usage, even in scientifi c literature.
It may simply be suggested that they be used
with caution and with an appreciation for an
international audience.
Summary
1. Wetlands are found on every continent
except Antarctica and in every climate, from
the tropics to the tundra.
2. It is practically quite diffi cult to quantify the
wetlands in the aerial and satellite imageries
which are now the most common sources of
data. The extent of the world’s wetlands is
generally assumed to be from 7 to 9 million
km
2 or about 4–6 % of the land surface of the
earth based on several estimates.
3. Other estimates of the global extent of the
wetlands have been developed from various
studies, notably, on the role of wetlands in
regulating the global biogeochemical cycles.
4. The US Department of Agriculture (USDA)
classifi ed wetlands into certain categories,
namely , (a) inland, (b) riparian or ephemeral,
(c) organic, (d) salt affected and (e) permafrost affected. They estimated that wetlands
cover c 13.7 % (18.8 million km
2 ) of the
earth’s surface.
5. The wetlands are said to account for c 4–6 %
of the total land surface of the earth. It is
quite diffi cult to estimate the loss of wetlands in the world. The estimates of loss
could be much higher in Europe, Canada,
Australia and Asia. In India, the loss of wetlands could be to the tune of approx. 70 % of
the total land area.
6. The historical terminology of wetlands has
been little confusing. Terms, such as billabong, bog, bottomland, carr, fen, lagoon,
mangal, marsh, mire, moor, muskeg, playa,
pocosin, pothole, reed swamp, slough,
swamp and vernal pool in English and Beel,
Haor, Anua, Baor, Jala, Holoni, Tal, Jheel,
etc., in many Asian languages, sometimes,
make confusions in the categorisation of
wetlands of the world.
7. It is not very well known regarding the rate at
which wetlands are lost in the global scenario. Many wetlands in the world had been
drained centuries ago. We have, perhaps, lost
c 50 % of the original wetlands on the earth.
8. Contrary to the west, the propensity of the
east was not to drain the valuable wetlands
entirely but to work within the aquatic
landscape, albeit in a heavily managed way.
9. Further, a number of common terms, such as
swamps, marsh, mire, have been used over the
years to describe different types of wetlands.
Many of these terms have their own meanings.
A marsh is known by most as a herbaceous
19 Wetlands of the World
Typha spp., which is a cosmopolitan wetland
plant, is called ‘cattail’ in America, ‘reed mace’
in the UK, ‘cumbungi’ in Australia, and ‘raupo’
and ‘bulrush’ in New Zealand. However, true bulrush is still called Scirpus spp. in North America.
It is believed that the European terminology is
older and richer. It distinguishes at least four
different kinds of freshwater wetlands, namely ,
(a) mineral-rich reed beds called reed swamps,
(b) wet grassland marshes, (c) fens and (d) bogs
or moors. According to some (e.g. Moore 1984 ),
all these wetland types are considered as ‘mires’.
It may be noted here that the European classifi cation is based on the amount of surface water
and nutrient fl ow (rheotrophy), type of vegetation, pH and peat-building characteristics.
On the other hand, as briefl y indicated above,
the classifi cation of wetlands in the Indian subcontinent and Bangladesh is based on certain
defi nite and simple observable criteria of retention of water in the wetlands. However, the three
local terms mentioned above may have other synonyms in different languages; but, the overall
basis of classifi cation based on retention of water
in the wetland generally remains the same.
On the basis of the above discussion, two
points could be emphasised regarding the use of
common terms in classifying wetland types:
(a) The physical and biotic characteristics grade
continuously from one of the wetland types
to the next. Hence, any classifi cation based
on common terms is, to some extent, arbitrary and may be avoided, if possible.
(b) The same term may refer to different systems
in different regions. The common terms seem
to be in usage, even in scientifi c literature.
It may simply be suggested that they be used
with caution and with an appreciation for an
international audience.
Summary
1. Wetlands are found on every continent
except Antarctica and in every climate, from
the tropics to the tundra.
2. It is practically quite diffi cult to quantify the
wetlands in the aerial and satellite imageries
which are now the most common sources of
data. The extent of the world’s wetlands is
generally assumed to be from 7 to 9 million
km
2 or about 4–6 % of the land surface of the
earth based on several estimates.
3. Other estimates of the global extent of the
wetlands have been developed from various
studies, notably, on the role of wetlands in
regulating the global biogeochemical cycles.
4. The US Department of Agriculture (USDA)
classifi ed wetlands into certain categories,
namely , (a) inland, (b) riparian or ephemeral,
(c) organic, (d) salt affected and (e) permafrost affected. They estimated that wetlands
cover c 13.7 % (18.8 million km
2 ) of the
earth’s surface.
5. The wetlands are said to account for c 4–6 %
of the total land surface of the earth. It is
quite diffi cult to estimate the loss of wetlands in the world. The estimates of loss
could be much higher in Europe, Canada,
Australia and Asia. In India, the loss of wetlands could be to the tune of approx. 70 % of
the total land area.
6. The historical terminology of wetlands has
been little confusing. Terms, such as billabong, bog, bottomland, carr, fen, lagoon,
mangal, marsh, mire, moor, muskeg, playa,
pocosin, pothole, reed swamp, slough,
swamp and vernal pool in English and Beel,
Haor, Anua, Baor, Jala, Holoni, Tal, Jheel,
etc., in many Asian languages, sometimes,
make confusions in the categorisation of
wetlands of the world.
7. It is not very well known regarding the rate at
which wetlands are lost in the global scenario. Many wetlands in the world had been
drained centuries ago. We have, perhaps, lost
c 50 % of the original wetlands on the earth.
8. Contrary to the west, the propensity of the
east was not to drain the valuable wetlands
entirely but to work within the aquatic
landscape, albeit in a heavily managed way.
9. Further, a number of common terms, such as
swamps, marsh, mire, have been used over the
years to describe different types of wetlands.
Many of these terms have their own meanings.
A marsh is known by most as a herbaceous
19 Wetlands of the World