Fisherman in Burma. (Photo by R. Glsco)
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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.
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Amazonian River Boat, Brazil 1999
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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
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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.
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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.
Profile of an Oxbow lake in the Peruvian Amazon
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.
The Death of Lac Alaotra, Madagascar
Review questions:
- Why is the Amazon River important to local people
- What is an oxbow lake?
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Continued: Threats to Tropical Rivers and Lakes
This article was written by Rhett A. Butler [bibliographic citation for this page] and was last updated on the most recent date listed in the column on the right side.
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CONTENTS
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WEEKLY NEWSLETTER
INTERACT
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Recent news
Brazilian mining company connected to Belo Monte dam voted worst corporation
(01/31/2012) The world's second largest mining company, Vale, has been given the dubious honor of being voted the world's most awful corporation in terms of human rights abuses and environmental destruction by the Public Eye Awards. Vale received over 25,000 votes online, likely prompted in part by its stake in the hugely controversial Brazilian mega-dam, Belo Monte, which is being constructed on the Xingu River. An expert panel gave a second award to British bank Barclay's for speculation on food prices, which the experts stated was worsening hunger worldwide.
Saving the world's biggest river otter
(01/30/2012) Charismatic, vocal, unpredictable, domestic, and playful are all adjectives that aptly describe the giant river otter (Pteronura brasiliensis), one of the Amazon's most spectacular big mammals. As its name suggest, this otter is the longest member of the weasel family: from tip of the nose to tail's end the otter can measure 6 feet (1.8 meters) long. Living in closely-knit family groups, sporting a complex range of behavior, and displaying almost human-like capricious moods, the giant river otter has captured a number of researchers and conservationists' hearts, including Dutch conservationist Jessica Groenendijk.
Brazil begins preliminary damming of Xingu River as protests continue
(01/19/2012) Damming of the Xingu River has begun in Brazil to make way for the eventual construction of the hugely controversial, Belo Monte dam. The Norte Energia (NESA) consortium has begun building coffer dams across the Xingu, which will dry out parts of the river before permanent damming, reports the NGO International Rivers. Indigenous tribes, who have long opposed the dam plans on their ancestral river, conducted a peaceful protest that interrupted construction for a couple hours.
Deforestation, climate change threaten the ecological resilience of the Amazon rainforest
(01/19/2012) The combination of deforestation, forest degradation, and the effects of climate change are weakening the resilience of the Amazon rainforest ecosystem, potentially leading to loss of carbon storage and changes in rainfall patterns and river discharge, finds a comprehensive review published in the journal Nature.
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Picture of the day: nearly-extinct turtle released into the wild in Cambodia
(01/18/2012) Only around 200 southern river terrapins (Batagur affinis) survive in the wild, but today at least the species got some good news. A female terrapin was released back into the Sre Ambel River with much fanfare after being caught by a local fishermen in Cambodia.
More rainforest news
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