521
an area estimated between 14,000,000 ha and
17,500,000 ha. in Latin America. Out of this, c
131,000 km
2 is fl ooded annually (Hamilton et al.
1996 ). The annual period of fl ooding is called
‘Cheia’. It ranges from March through May.
During this period, the wetland supports luxurious aquatic plant and animal life. Flooding is followed by dry season called ‘seca’. It ranges from
September to November. During this period, the
Pantanal reverts back to the vegetation which is
typical of dry savannas. There are also specifi c
terms for the period of rising waters, namely,
‘enchente’, from December through February and
the period of declining waters, namely, ‘vazante’,
from June through August (Heckman 1994 ).
There is also an asynchronous pattern of fl ooding
in the Pantanal (Hamilton et al. 1996 ). Annual
rainfall over the fl ood basin is between 1,000 and
1,500 mm with most rainfall occurring between
November and March. But it is said to be fed by
the upper Paraguay River. During the rainy season, the water in the Pantanal basin (particularly,
in the Paraguay River portion of the Pantanal)
rises between 2 and 5 m. Flood waters tend to
fl ow slowly (2–10 cm per second) due to the low
gradients and high resistance offered by the dense
vegetation. Its average temperature is 25 °C, but
temperatures can fl uctuate from 0 to 40 °C.
Ecology and Hydrology
Floodplain ecosystems such as the Pantanal are
defi ned by their seasonal inundation and desiccation. Accordingly, the soils range from high levels
of sand in higher areas to higher amounts of clay
and silt in riverine areas. It may be noted here that
when rising river water fi rst comes in contact
with previously dry soil, the water becomes
oxygen depleted, thus rendering the aquatic
environment anoxic. Many natural fi sh kills
may occur, if there is no oxygenated water
refuge available. The reason for this seems to be
speculative. It may be due to the growth of toxinproducing bacteria in the deoxygenated water
rather than as a direct result of lack of oxygen.
Further, there exist various subregional ecosystems each with distinct hydrological, geological and ecological characteristics. Up to 12 of
them have been defi ned.
Biota
The Pantanal plains are also fertile and farmable
like the Nile Delta. Eighty percent of the Pantanal
fl oodplains are submerged during the rainy season, nurturing an astonishing biologically diverse
collection of aquatic plants and helping support a
dense array of animal species. Increase in water
level during the rainy season nourishes the primary producers of Pantanal, which, in turn, benefi ts other biota as well. However , the Pantanal
inevitably cuts a lower profi le as compared to the
Amazon rainforest to its north, although the ecosystems of the former are inevitably precious.
Human interventions indeed cause problems for
the wetland.
The biota spread across the landscape during
the wet season and concentrate in fewer wet areas
in a food chain frenzy during the dry season. The
Pantanal is legendary for its bird life, even though
it is, possibly, one of the least known regions in
the globe. Pantanal is a home to about 650–700
species of birds (Por 1995 ). There are said to be
13 species of herons and egrets, 3 species of
storks, 6 species each of spoonbills and ducks, 5
species of kingfi shers, etc. The bird ‘ jabiru ’ is the
symbol of the Pantanal. It is the largest fl ying
bird of the western hemisphere. In addition to the
above, the Pantanal supports an abundant population of the ‘caiman’ , which is said to be a relative
of the North American crocodile. It also supports
the ‘capybara’, which is one of the largest rodents
of the region.
Flora
The vegetation of the Pantanal is often called the
‘Pantanal complex’ which is a mixture of plant
communities typical of a variety of surrounding biomes. These include (a) moist tropical
Amazonian rainforest plants, (b) semiarid woodland plants typical of northeast Brazil, (c) Brazilian
cerrado savanna plants and (d) plants of the Chaco
savannas of Bolivia and Paraguay. Forests usually
occur at higher altitudes of the region, while grasslands cover the seasonally inundated areas. The
key-limiting factors for growth are inundation and,
even more importantly, water stress during the dry
season. The Pantanal ecosystem is a habitat for
3,500 known plant species.
23.7 Wetlands of South America
an area estimated between 14,000,000 ha and
17,500,000 ha. in Latin America. Out of this, c
131,000 km
2 is fl ooded annually (Hamilton et al.
1996 ). The annual period of fl ooding is called
‘Cheia’. It ranges from March through May.
During this period, the wetland supports luxurious aquatic plant and animal life. Flooding is followed by dry season called ‘seca’. It ranges from
September to November. During this period, the
Pantanal reverts back to the vegetation which is
typical of dry savannas. There are also specifi c
terms for the period of rising waters, namely,
‘enchente’, from December through February and
the period of declining waters, namely, ‘vazante’,
from June through August (Heckman 1994 ).
There is also an asynchronous pattern of fl ooding
in the Pantanal (Hamilton et al. 1996 ). Annual
rainfall over the fl ood basin is between 1,000 and
1,500 mm with most rainfall occurring between
November and March. But it is said to be fed by
the upper Paraguay River. During the rainy season, the water in the Pantanal basin (particularly,
in the Paraguay River portion of the Pantanal)
rises between 2 and 5 m. Flood waters tend to
fl ow slowly (2–10 cm per second) due to the low
gradients and high resistance offered by the dense
vegetation. Its average temperature is 25 °C, but
temperatures can fl uctuate from 0 to 40 °C.
Ecology and Hydrology
Floodplain ecosystems such as the Pantanal are
defi ned by their seasonal inundation and desiccation. Accordingly, the soils range from high levels
of sand in higher areas to higher amounts of clay
and silt in riverine areas. It may be noted here that
when rising river water fi rst comes in contact
with previously dry soil, the water becomes
oxygen depleted, thus rendering the aquatic
environment anoxic. Many natural fi sh kills
may occur, if there is no oxygenated water
refuge available. The reason for this seems to be
speculative. It may be due to the growth of toxinproducing bacteria in the deoxygenated water
rather than as a direct result of lack of oxygen.
Further, there exist various subregional ecosystems each with distinct hydrological, geological and ecological characteristics. Up to 12 of
them have been defi ned.
Biota
The Pantanal plains are also fertile and farmable
like the Nile Delta. Eighty percent of the Pantanal
fl oodplains are submerged during the rainy season, nurturing an astonishing biologically diverse
collection of aquatic plants and helping support a
dense array of animal species. Increase in water
level during the rainy season nourishes the primary producers of Pantanal, which, in turn, benefi ts other biota as well. However , the Pantanal
inevitably cuts a lower profi le as compared to the
Amazon rainforest to its north, although the ecosystems of the former are inevitably precious.
Human interventions indeed cause problems for
the wetland.
The biota spread across the landscape during
the wet season and concentrate in fewer wet areas
in a food chain frenzy during the dry season. The
Pantanal is legendary for its bird life, even though
it is, possibly, one of the least known regions in
the globe. Pantanal is a home to about 650–700
species of birds (Por 1995 ). There are said to be
13 species of herons and egrets, 3 species of
storks, 6 species each of spoonbills and ducks, 5
species of kingfi shers, etc. The bird ‘ jabiru ’ is the
symbol of the Pantanal. It is the largest fl ying
bird of the western hemisphere. In addition to the
above, the Pantanal supports an abundant population of the ‘caiman’ , which is said to be a relative
of the North American crocodile. It also supports
the ‘capybara’, which is one of the largest rodents
of the region.
Flora
The vegetation of the Pantanal is often called the
‘Pantanal complex’ which is a mixture of plant
communities typical of a variety of surrounding biomes. These include (a) moist tropical
Amazonian rainforest plants, (b) semiarid woodland plants typical of northeast Brazil, (c) Brazilian
cerrado savanna plants and (d) plants of the Chaco
savannas of Bolivia and Paraguay. Forests usually
occur at higher altitudes of the region, while grasslands cover the seasonally inundated areas. The
key-limiting factors for growth are inundation and,
even more importantly, water stress during the dry
season. The Pantanal ecosystem is a habitat for
3,500 known plant species.
23.7 Wetlands of South America