279
with their surroundings. A salt marsh may be
defi ned as a ‘natural or semi-natural halophytic grassland and dwarf brushwood on
the alluvial sediments bordering saline water
bodies whose water level fl uctuates either
tidally or non-tidally’ . An important feature
of salt marshes is the presence of panes
(pans). Further, the salt marsh ecosystem has
diverse biological components which include
plants, animals and microbes in the marsh. It
also includes plankton, invertebrates and fi sh
in the tidal creeks, panes and estuaries. A salt
marsh generally has high annual gross and
net primary productivity of macrophytes.
6. The freshwater (FW) coastal wetlands are
unique ecosystems which combine many
features of both salt marshes and FW inland
marshes. This type of wetlands are situated
inland from the tidal salt marshes but still
close enough to the coast to experience tidal
effects. Their biota refl ect the increased
diversity which is made possible by the
reduction in the salt stress found in salt
marshes. Plant diversity is high. More birds
use these marshes than any other marsh type.
However, they are more prone to human
interference due to their proximity to urban
areas. The tidal FW marshes could be
grouped into three major types. Further, the
tidal FW marshes generally receive the same
‘tidal subsidy’ as coastal salt marshes but
without the salt stress.
7. Coastal FW wetlands are known to occur on
different types of substrates. However, their
recent geological history is similar in spite
of regional differences. The contemporary
coastal marshes are said to be recent
(Holocene) in origin. They occurred in the
river valleys which were isolated during the
Pleistocene periods of lowered sea levels.
Subsequently, when the sea level rose after the
last glaciation (15,000–5,000 BP), FW coastal
marshes had possibly expanded rapidly.
8. Mangrove swamps (wetlands) are signifi cant
ecosystems in the world. They generally lie
between 25° N and 25° S latitudes. Broadly,
mangroves are divided into two groups,
namely , (a) the Old World mangrove swamps
and (b) the New World and West African
mangrove swamps. The development of
mangrove swamps is the result of topography, substrate, freshwater hydrology and
tidal action. Further, the mangrove swamps
are found under conditions which provide a
wide range of salinity. There are different
types of mangrove wetlands. Each has a
unique set of topographic and hydrodynamic conditions. It is believed that the tidal
salt marshes are replaced by the mangrove
swamps in subtropical and tropical regions
of the world. It is important to note here that
the word ‘mangrove’ refers both to the wetland itself and to the salt-tolerant trees which
dominate these wetlands. Mangrove swamps
are dominant coastal ecosystems, which
cover an area of c 240,000 km
2 throughout
the world.
9. Freshwater inland marshes are, perhaps, the
most diverse of the marsh types in the globe.
They are nontidal freshwater systems dominated by grasses, sedges and other freshwater (FW) emergent hydrophytes. They vary
generally in their origin and the driving
hydrologic forces. They vary in size from
small pothole marshes (of <1.0 ha) to the
enormous tropical wetlands and the immense
sawgrass monocultures of the Florida
Everglades. There is variation in nomenclature for inland FW wetlands, e.g. in Europe,
the term ‘reed swamp’ is often used to
describe one type of FW marsh dominated
by Phragmites spp., and in the USA, the
word ‘swamp’ usually refers to a forested
wetland. There are several groups of FW
marshes, notably, the Prairie potholes, the
Nebraska Sandhills, etc. They had originated
in millions of depression formed by glacial
action. Some of the types of marshes are the
near coast marshes , which are large tracts of
FW marshes concentrated along the northern
coast of the Gulf of Mexico and along the
South Atlantic Coast of the USA. The
Everglades of South Florida is the largest
single marsh system in the USA, occupying
an area of almost 10,000 km
2 from Lake
Okeechobee to the brackish marshes and
18.9 Riparian Ecosystems
with their surroundings. A salt marsh may be
defi ned as a ‘natural or semi-natural halophytic grassland and dwarf brushwood on
the alluvial sediments bordering saline water
bodies whose water level fl uctuates either
tidally or non-tidally’ . An important feature
of salt marshes is the presence of panes
(pans). Further, the salt marsh ecosystem has
diverse biological components which include
plants, animals and microbes in the marsh. It
also includes plankton, invertebrates and fi sh
in the tidal creeks, panes and estuaries. A salt
marsh generally has high annual gross and
net primary productivity of macrophytes.
6. The freshwater (FW) coastal wetlands are
unique ecosystems which combine many
features of both salt marshes and FW inland
marshes. This type of wetlands are situated
inland from the tidal salt marshes but still
close enough to the coast to experience tidal
effects. Their biota refl ect the increased
diversity which is made possible by the
reduction in the salt stress found in salt
marshes. Plant diversity is high. More birds
use these marshes than any other marsh type.
However, they are more prone to human
interference due to their proximity to urban
areas. The tidal FW marshes could be
grouped into three major types. Further, the
tidal FW marshes generally receive the same
‘tidal subsidy’ as coastal salt marshes but
without the salt stress.
7. Coastal FW wetlands are known to occur on
different types of substrates. However, their
recent geological history is similar in spite
of regional differences. The contemporary
coastal marshes are said to be recent
(Holocene) in origin. They occurred in the
river valleys which were isolated during the
Pleistocene periods of lowered sea levels.
Subsequently, when the sea level rose after the
last glaciation (15,000–5,000 BP), FW coastal
marshes had possibly expanded rapidly.
8. Mangrove swamps (wetlands) are signifi cant
ecosystems in the world. They generally lie
between 25° N and 25° S latitudes. Broadly,
mangroves are divided into two groups,
namely , (a) the Old World mangrove swamps
and (b) the New World and West African
mangrove swamps. The development of
mangrove swamps is the result of topography, substrate, freshwater hydrology and
tidal action. Further, the mangrove swamps
are found under conditions which provide a
wide range of salinity. There are different
types of mangrove wetlands. Each has a
unique set of topographic and hydrodynamic conditions. It is believed that the tidal
salt marshes are replaced by the mangrove
swamps in subtropical and tropical regions
of the world. It is important to note here that
the word ‘mangrove’ refers both to the wetland itself and to the salt-tolerant trees which
dominate these wetlands. Mangrove swamps
are dominant coastal ecosystems, which
cover an area of c 240,000 km
2 throughout
the world.
9. Freshwater inland marshes are, perhaps, the
most diverse of the marsh types in the globe.
They are nontidal freshwater systems dominated by grasses, sedges and other freshwater (FW) emergent hydrophytes. They vary
generally in their origin and the driving
hydrologic forces. They vary in size from
small pothole marshes (of <1.0 ha) to the
enormous tropical wetlands and the immense
sawgrass monocultures of the Florida
Everglades. There is variation in nomenclature for inland FW wetlands, e.g. in Europe,
the term ‘reed swamp’ is often used to
describe one type of FW marsh dominated
by Phragmites spp., and in the USA, the
word ‘swamp’ usually refers to a forested
wetland. There are several groups of FW
marshes, notably, the Prairie potholes, the
Nebraska Sandhills, etc. They had originated
in millions of depression formed by glacial
action. Some of the types of marshes are the
near coast marshes , which are large tracts of
FW marshes concentrated along the northern
coast of the Gulf of Mexico and along the
South Atlantic Coast of the USA. The
Everglades of South Florida is the largest
single marsh system in the USA, occupying
an area of almost 10,000 km
2 from Lake
Okeechobee to the brackish marshes and
18.9 Riparian Ecosystems