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Fisherman in Burma. (Photo by R. Glsco)
IMPORTANCE OF RAINFOREST RIVERS TO PEOPLE
Tropical rivers have always played an essential role in the ecology
of the rainforest, but they have also been important in the lives of forest and non-forest peoples. Before the arrival of the Europeans,
sprawling civilizations and smaller societies formed along major waterways which served as a means of transport
and communication, a route for trade, and a source of fish and fresh water. However, because of their location along
major rivers, such settlements were the first to disappear, either directly affected by warfare or indirectly affected
by the onslaught of European diseases.
Today, large tropical rivers remain important forms of infrastructure providing a cheap, reliable, and easy means
for transportation and communication. Major rivers ports like Iquitos, Peru, and Manaus, Brazil, are trade centers
where forest products are exchanged for outside goods. Often, the only access to such ports, isolated by the surrounding
forest, is by water or air. For example, there are no roads leading into to Iquitos and all construction materials,
automobiles, and other essentials must be shipped into the city by river or air.
Amazonian River Boat, Brazil 1999
Besides providing a means for commerce and communication, tropical rivers are a key source of protein, in the form
of fish, for the population. However in some areas, fishermen report smaller catches as regional overfishing takes
its toll. The river also provides services for city dwellers by fertilizing the surrounding soils every flood season
and by taking away the tons of human waste and pollutants that city dwellers dump into the river.
Tropical fish provide an important source of income for many city dwellers, especially in the Amazon, which is home
to some 3,000 species of fish. Many of the fish seen in temperate-zone aquarium shops are imported from Brazil and
Peru.
LAKES
Peruvian Amazon river
Aerial view of a meandering river in the rainforest of Peru. If you look closely, two oxbow lakes are visible towards the center of the image. One is considerably "darker" than the other, but both are isolated from the main channel of the river.
The vast majority of natural lakes in lowland rainforests are oxbow lakes. An oxbow lake is a crescent-shaped lake formed when a river changes course. In lowland rainforests like the parts of the Amazon where soft alluvial soils dominate, meandering rivers gradually shift due to erosion and sediment deposition. Oxbow lakes typically form when loops in the river become so extreme that the main channel erodes a new straighter route, leaving the river bend apart from the river. As time passes, the oxbow lake becomes increasingly distant from the main channel. Water conditions change as the water stagnates.
The characteristics of an oxbow lake generally depend on its age. Younger oxbow lakes may be "flushed" by river currents, especially during the flood season. These lakes tend to be slightly more turbid (less transparent) and less acidic than older lakes more distant from the river channel.
Oxbow lakes are key habitats for many species of fish and aquatic animals. A number of popular tropical aquarium fish species live exclusively in oxbow lakes, which also serve as the primary habitat for giant river otters in South America.
Free-standing lakes in the rainforest also exist, though they are not as abundant as tropical rivers. Like oxbow lakes,
the tend to become more acidic with time as vegetation decays.
New species of river dolphin discovered in the Amazon
(4/30/2008) Researchers have identified a new species of river dolphin in the Bolivian Amazon according to the Whale and Dolphin Conservation Society (WDCS). The announcement was made at a conservation workshop in Santa Cruz de la Sierra in Bolivia.
Corn ethanol is worsening the Gulf dead zone
(3/10/2008) Proposed legislation that will expand corn-ethanol production in the United States will worsen the growing "dead zone" in the Gulf of Mexico and hurt marine fisheries, report researchers writing in the Proceedings of the National Academy of Sciences (PNAS).
