192
impact of extreme pollution and altered
hydrology associated with housing, feeding
and transporting a large population. Many
wetlands are easily drained out and turned
into dry lands by human intervention.
Likewise, altered hydrology or increased
run-off may cause wetlands to develop where
they were not found before. Some animals,
e.g. beavers and alligators, may play a role in
developing wetlands. Wetlands are generally
very easily disturbed. It is often diffi cult to
identify them after such disturbances. This is
particularly applicable for wetlands which
have been farmed for a number of years.
‘Wetlands are a half way world between terrestrial and aquatic ecosystems and exhibit some
of the characteristics of each’ (Smith 1980 ). They
form part of a continuous gradient between
uplands and open water. Thus, the upper and the
lower limits of wetland excursion are arbitrary
boundaries in any defi nition. Consequently, few
defi nitions adequately describe all wetlands.
The defi nition of wetland has been made controversial particularly by the variable ‘frequency
of fl ooding’. However, there is no single universally recognised defi nition of a wetland mainly
because wetland characteristics grade continuously from aquatic to terrestrial system. This
void has led to confusion and inconsistencies in
the management, classifi cation and inventorying
of wetland systems. However, inconsistencies
may be no surprise when we consider the diversity of types, sizes, locations and conditions of
wetlands in different countries of the world.
11.7 Defi nitions of Wetlands
Wetlands have many unique features. The most
unique of these are the presence of standing water
for some period during the growing season,
unique soil conditions and organisms, especially
vegetation which is adapted to or tolerant of saturated soils. There is no easy defi nition of wetlands. They have a considerable range of
hydrologic conditions. They are found along a
gradient at the margins of well-defi ned uplands
and deep water systems. They have great
variations in size, location and human infl uence.
Terms, such as swamp, marsh, fen and bog, have
been in use in common speech for centuries and
are frequently used and misused today. Formal
defi nitions of wetlands have been developed by
several federal agencies in the USA, by scientists
in Canada and the USA, etc. Also, defi nition of
wetland has been developed through an international treaty called the Ramsar Convention.
These defi nitions include considerable details
and are used for both scientifi c and management
purposes. Expectations may be there for an absolute answer to ‘What is a wetland?’ However,
legal defi nitions involving wetland protection are
becoming increasingly comprehensive.
An uninitiated may ask a very common question about a wetland, ‘what exactly a wetland
is?’, or ‘is that the same as a swamp?’ These are,
no doubt, surprisingly good questions. And it is
not altogether clear whether they have been completely answered by wetland scientists and managers. There are many wetland defi nitions and
terms. These are often confusing and contradictory. However, defi nitions are important both for
the scientifi c understanding of these systems and
for their proper management.
When the drainage of the wetlands was the
order of the day and the norm during the nineteenth century, a wetland defi nition was unimportant because it was considered desirable to
produce uplands from wetlands by draining them
out. In fact, the word ‘wetland’ did not come in
common use until the mid-twentieth century. One
of the fi rst references to the word was in the publication Wetlands of the United States (Shaw and
Fredine 1956 ). Before that, wetlands were
referred to by many common terms which had
been developed in the nineteenth century and
before. Some of these terms are marsh, swamp,
bog, fen, mire, moor, etc. Further, the values of
the ‘wetlands’ were recognised in the early
1970s. But, still, there was little interest in precise defi nitions of wetlands, until it was realised
that a better accounting of the remaining wetland
resources was needed and defi nitions were necessary to achieve that inventory. The need for precision became even greater when national and
international laws and regulations pertaining to
11 Wetlands in the Landscape: Their History, Defi nitions, Origin and Evolution
impact of extreme pollution and altered
hydrology associated with housing, feeding
and transporting a large population. Many
wetlands are easily drained out and turned
into dry lands by human intervention.
Likewise, altered hydrology or increased
run-off may cause wetlands to develop where
they were not found before. Some animals,
e.g. beavers and alligators, may play a role in
developing wetlands. Wetlands are generally
very easily disturbed. It is often diffi cult to
identify them after such disturbances. This is
particularly applicable for wetlands which
have been farmed for a number of years.
‘Wetlands are a half way world between terrestrial and aquatic ecosystems and exhibit some
of the characteristics of each’ (Smith 1980 ). They
form part of a continuous gradient between
uplands and open water. Thus, the upper and the
lower limits of wetland excursion are arbitrary
boundaries in any defi nition. Consequently, few
defi nitions adequately describe all wetlands.
The defi nition of wetland has been made controversial particularly by the variable ‘frequency
of fl ooding’. However, there is no single universally recognised defi nition of a wetland mainly
because wetland characteristics grade continuously from aquatic to terrestrial system. This
void has led to confusion and inconsistencies in
the management, classifi cation and inventorying
of wetland systems. However, inconsistencies
may be no surprise when we consider the diversity of types, sizes, locations and conditions of
wetlands in different countries of the world.
11.7 Defi nitions of Wetlands
Wetlands have many unique features. The most
unique of these are the presence of standing water
for some period during the growing season,
unique soil conditions and organisms, especially
vegetation which is adapted to or tolerant of saturated soils. There is no easy defi nition of wetlands. They have a considerable range of
hydrologic conditions. They are found along a
gradient at the margins of well-defi ned uplands
and deep water systems. They have great
variations in size, location and human infl uence.
Terms, such as swamp, marsh, fen and bog, have
been in use in common speech for centuries and
are frequently used and misused today. Formal
defi nitions of wetlands have been developed by
several federal agencies in the USA, by scientists
in Canada and the USA, etc. Also, defi nition of
wetland has been developed through an international treaty called the Ramsar Convention.
These defi nitions include considerable details
and are used for both scientifi c and management
purposes. Expectations may be there for an absolute answer to ‘What is a wetland?’ However,
legal defi nitions involving wetland protection are
becoming increasingly comprehensive.
An uninitiated may ask a very common question about a wetland, ‘what exactly a wetland
is?’, or ‘is that the same as a swamp?’ These are,
no doubt, surprisingly good questions. And it is
not altogether clear whether they have been completely answered by wetland scientists and managers. There are many wetland defi nitions and
terms. These are often confusing and contradictory. However, defi nitions are important both for
the scientifi c understanding of these systems and
for their proper management.
When the drainage of the wetlands was the
order of the day and the norm during the nineteenth century, a wetland defi nition was unimportant because it was considered desirable to
produce uplands from wetlands by draining them
out. In fact, the word ‘wetland’ did not come in
common use until the mid-twentieth century. One
of the fi rst references to the word was in the publication Wetlands of the United States (Shaw and
Fredine 1956 ). Before that, wetlands were
referred to by many common terms which had
been developed in the nineteenth century and
before. Some of these terms are marsh, swamp,
bog, fen, mire, moor, etc. Further, the values of
the ‘wetlands’ were recognised in the early
1970s. But, still, there was little interest in precise defi nitions of wetlands, until it was realised
that a better accounting of the remaining wetland
resources was needed and defi nitions were necessary to achieve that inventory. The need for precision became even greater when national and
international laws and regulations pertaining to
11 Wetlands in the Landscape: Their History, Defi nitions, Origin and Evolution