River in Madre de Dios, Peru. Click image for related pictures. (Photo by R. Butler)
By Rhett Butler
| Last updated July 31, 2012
Tropical rainforests have some of the largest rivers in the world, like the Amazon, Madeira, Mekong, Negro, Orinoco,
and Congo (Zaire), because of the tremendous amount of precipitation their watersheds receive. These mega-rivers
are fed by countless smaller tributaries, streams, and creeks. For example, the Amazon alone has some 1,100 tributaries,
17 of which are over 1,000 miles long. Although large tropical rivers are fairly uniform in appearance and water
composition, their tributaries vary greatly. Many tropical rivers and streams have extreme high and low water levels
that occur at different parts of the year.
In addition to rivers, rainforests have conventional, free-standing lakes and so-called oxbow lakes, formed when
a river changes course. These lakes are home to species adapted to the quiet, stagnant conditions.
Tropical waters, whether they be giant rivers, streams, or oxbow lakes, are almost as rich in animal species as
the rainforests that surround them. But they, too, are increasingly threatened by human activities, including
pollution, siltation resulting from deforestation, hydroelectric projects, and over-harvesting of resident species.
Waterways off the Rio Negro in Brazil. (Courtesy of NASA)
- Why are some of the world's largest rivers found in tropical regions?
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Selection of information sources
Richard Spruce's opening quotation (made around 1850) is found in One River (New York: Touchstone, 1996) by Wade Davis.
Pet fish invade ecosystem, upending nutrients and impoverishing fishers
(10/02/2013) If you, or someone you know, owns a freshwater aquarium, chances are you have seen the peculiar little creature attached face-first to the glass in effort to find a morsel of algae. This algae eater, popularly known as the sucker fish, is the sailfin catfish, or plecos. It is one of the most commonly purchased fish in the freshwater aquarium fish trade, and, according to recent research in The Royal Society B, aquarists often reintroduce the sucker-fish into the wild with detrimental consequences.
Judge halts construction of Amazon dam on Brazil's Teles Pires river
(09/19/2013) A federal judge in Brazil has ordered the suspension of construction activities on the Teles Pires due to shortcomings in the environmental licensing process, including the project's impacts on three local tribes, reports International Rivers.
Forgotten species: the arapaima or 'dinosaur fish'
(07/15/2013) Let's go back some 14,000 years (or up to 50,000 depending on who you talk to), since this is the first time humans encountered the meandering, seemingly endless river system of the Amazon. Certainly, the world's first Amazonians would have been astounded by the giant beasts of the region, including ground sloths and mastodons (both now extinct), as well as giant anteaters, armadillos, and tapirs, currently the biggest land animal on the continent. But these first explorers might have been even more surprised by what dwelled in the rivers: anaconda, caiman, and the arapaima. Wait, the what?
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