194
introduce the concepts of hydric soils and hydrophytes . It served as the impetus for scientists and
managers to defi ne those terms more accurately
(NRC 1995 ).
11.7.5 Canadian Defi nitions
of Wetland
The Canadians deal with vast areas of inland
northern peatlands. They have developed a
specifi c national defi nition of wetlands. Zoltai
( 1979 ), at a workshop of the Canadian National
Wetlands Working Group, had defi ned
‘wetland’ as
areas where wet soils are prevalent, having a water
table near or above the mineral soil for the most
part of the thawed season, supporting a hydrophytic vegetation.
Further, Tarnocai ( 1979 ), at the same workshop, had presented the definition which is
used in the Canadian Wetland Registry, which
is an inventory and data bank on Canadian
wetlands. This definition is almost similar to
the two definitions which have been formally
published in the book entitled Wetlands of
Canada by the National Wetlands Working
Group ( 1988 ).
Later, Zoltai ( 1988 ) defi ned a wetland as
‘Land that has the water table at, near, or above
the land surface or which is saturated for a long
enough period to promote wetland or aquatic
processes as indicated by hydric soils, hydrophytic vegetation, and various kinds of biological
activities which are adapted to the wet environment’. He had clarifi ed the wet and dry extremes
of wetlands into two types:
(a) Shallow open waters, generally <2 m
(b) Periodically inundated areas only if waterlogged conditions dominate throughout the
development of the ecosystem
Tarnacoi et al. ( 1988 ) offered a slightly
re-worded defi nition. This defi nition is said to
form the basis of the Canadian wetland classifi -
cation system. This defi nition was repeated by
NRC ( 1995 ) and by Warner and Rubec ( 1997 ).
This is said to be the offi cial defi nition of ‘wetlands’ in Canada. It could be stated as follows:
Land that is saturated with water long enough to
promote wetland or aquatic processes as indicated
by poorly drained soils, hydrophytic vegetation
and various kinds of biological activities which are
adapted to a wet environment.
11.7.6 Defi nition of US National
Academy of Sciences
There had been renewed regulatory controversies
in the USA, during the early 1990s, as to what
constitutes a ‘wetland’. The US Congress had,
thus, requested the private non-profi t National
Academy of Sciences (NAS) to appoint a committee through its principal operating agency, the
National Research Council (NRC). The task was
to undertake a scientifi c review of scientifi c
aspects of wetland characterisation. The committee had started its work in September 1993. The
terms of review were as follows:
(a) The adequacy of the existing defi nition of
wetlands
(b) The adequacy of science for evaluating the
hydrologic, biological and other ways in
which the wetlands function
(c) Regional variations in wetland defi nitions
The report of the committee, entitled, Wetlands :
Characteristics and Boundaries (NRC 1995 ),
included yet another scientifi c defi nition which is
referred to as ‘reference defi nition’. This defi nition
was meant to stand ‘outside the context of any particular agency, policy of regulation’ (NRC 1995 ).
A wetland is an ecosystem which depends upon
constant or recurrent, shallow inundation or saturation at or near the surface of the substrate. The
minimum essential characteristics of a wetland are
recurrent, sustained inundation or saturation at or
near the surface. Further, some of the common
diagnostic features of wetlands are hydric soils and
hydrophytic vegetations.
This is said to be one of the most comprehensively developed scientifi c defi nitions of wetland.
However, little formal use has been made of this
defi nition.
11 Wetlands in the Landscape: Their History, Defi nitions, Origin and Evolution
introduce the concepts of hydric soils and hydrophytes . It served as the impetus for scientists and
managers to defi ne those terms more accurately
(NRC 1995 ).
11.7.5 Canadian Defi nitions
of Wetland
The Canadians deal with vast areas of inland
northern peatlands. They have developed a
specifi c national defi nition of wetlands. Zoltai
( 1979 ), at a workshop of the Canadian National
Wetlands Working Group, had defi ned
‘wetland’ as
areas where wet soils are prevalent, having a water
table near or above the mineral soil for the most
part of the thawed season, supporting a hydrophytic vegetation.
Further, Tarnocai ( 1979 ), at the same workshop, had presented the definition which is
used in the Canadian Wetland Registry, which
is an inventory and data bank on Canadian
wetlands. This definition is almost similar to
the two definitions which have been formally
published in the book entitled Wetlands of
Canada by the National Wetlands Working
Group ( 1988 ).
Later, Zoltai ( 1988 ) defi ned a wetland as
‘Land that has the water table at, near, or above
the land surface or which is saturated for a long
enough period to promote wetland or aquatic
processes as indicated by hydric soils, hydrophytic vegetation, and various kinds of biological
activities which are adapted to the wet environment’. He had clarifi ed the wet and dry extremes
of wetlands into two types:
(a) Shallow open waters, generally <2 m
(b) Periodically inundated areas only if waterlogged conditions dominate throughout the
development of the ecosystem
Tarnacoi et al. ( 1988 ) offered a slightly
re-worded defi nition. This defi nition is said to
form the basis of the Canadian wetland classifi -
cation system. This defi nition was repeated by
NRC ( 1995 ) and by Warner and Rubec ( 1997 ).
This is said to be the offi cial defi nition of ‘wetlands’ in Canada. It could be stated as follows:
Land that is saturated with water long enough to
promote wetland or aquatic processes as indicated
by poorly drained soils, hydrophytic vegetation
and various kinds of biological activities which are
adapted to a wet environment.
11.7.6 Defi nition of US National
Academy of Sciences
There had been renewed regulatory controversies
in the USA, during the early 1990s, as to what
constitutes a ‘wetland’. The US Congress had,
thus, requested the private non-profi t National
Academy of Sciences (NAS) to appoint a committee through its principal operating agency, the
National Research Council (NRC). The task was
to undertake a scientifi c review of scientifi c
aspects of wetland characterisation. The committee had started its work in September 1993. The
terms of review were as follows:
(a) The adequacy of the existing defi nition of
wetlands
(b) The adequacy of science for evaluating the
hydrologic, biological and other ways in
which the wetlands function
(c) Regional variations in wetland defi nitions
The report of the committee, entitled, Wetlands :
Characteristics and Boundaries (NRC 1995 ),
included yet another scientifi c defi nition which is
referred to as ‘reference defi nition’. This defi nition
was meant to stand ‘outside the context of any particular agency, policy of regulation’ (NRC 1995 ).
A wetland is an ecosystem which depends upon
constant or recurrent, shallow inundation or saturation at or near the surface of the substrate. The
minimum essential characteristics of a wetland are
recurrent, sustained inundation or saturation at or
near the surface. Further, some of the common
diagnostic features of wetlands are hydric soils and
hydrophytic vegetations.
This is said to be one of the most comprehensively developed scientifi c defi nitions of wetland.
However, little formal use has been made of this
defi nition.
11 Wetlands in the Landscape: Their History, Defi nitions, Origin and Evolution