The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers a large area spreading across the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, and Venezuela, as well as the territory of French Guiana.Goulding, M., Barthem, R. B. and Duenas, R. (2003). The Smithsonian Atlas of the Amazon, Smithsonian Books
Most of the basin is covered by the Amazon rainforest, also known as Amazonia. With a area of dense tropical forest, it is the largest rainforest in the world. The Amazon basin is the most biodiverse region in the world, being home to many of the Earth's plant, mammal, bird, reptile, amphibian, fish and insect species. While being very biodiverse the majority of the Amazon basin is sparsely populated by humans with the exceptions of cities such as Manaus and Belém. There are many indigenous communities who represent many different cultures and languages. For the people living in the Amazon basin fishing and agriculture are a very important livelihood.
Geography
The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. The Amazon River begins in the Andes Mountains at the west of the basin with its main tributary the Marañón River and Apurimac River in Peru. The highest point in the watershed of the Amazon is the second biggest peak of Yerupajá at .
The Amazon River basin occupies the entire central and eastern area of South America, lying to the east of the Andes mountain range and extending from the Guyana Plateau in the north to the Brazilian Plateau in the south.
With a length of about 6400 km before it drains into the Atlantic Ocean, it is one of the two longest rivers in the world. A team of scientists has claimed that the Amazon is longer than the Nile, but debate about its exact length continues.
The Amazon system transports the largest volume of water of any river system, accounting for about 20% of the total water carried to the oceans by rivers. Some of the Amazon rainforests are deforested because of an increase in cattle ranches and soybean fields. The Amazon basin formerly flowed west to the Pacific Ocean until the Andes formed, causing the basin to flow eastward towards the Atlantic Ocean.
Politically the basin is divided into Peruvian Amazonia, Amazônia Legal of Brazil, the Amazon natural region of Colombia, Amazonas (Venezuelan state), and parts of Bolivia and Ecuador.
+Distribution of the Amazon River basin area and discharge between countriesCountryStateArea (km2)(%)Discharge (km3)(%)Bolivia724,00010.42914.0Brazil4,674,61967.54,167.357.2Acre164,1233.5144.22.0Amapá44,8701.057.70.8Amazonas1,559,15933.31,848.325.4 Brasília1,0100.02Goiás212,1314.596.71.3Maranhão39,3960.89.40.1Mato Grosso723,47015.5490.66.7Pará1,190,14725.51,053.114.5Rondônia237,5915.08140.61.9Roraima224,3014.8211.62.9 Tocantins278,4216.0115.11.6Ecuador146,6882.1258.43.6Guyana12,2240.28.80.1Colombia345,2935.075510.4Peru967,17614.01,739.523.9Venezuela53,0000.860.00.8Amazon basin6,923,000100.07,280100.0
Plant life
The Amazon basin is home to over 40,0000 species of plants. Plant growth is quite dense and its variety of animal inhabitants is comparatively high due to the heavy rainfall and the dense and extensive evergreen and coniferous forests. Little sunlight reaches the ground due to the dense roof of canopy by plants. The ground remains dark and damp and only shade-tolerant vegetation will grow here. Orchids and bromeliads exploit trees and other plants to get closer to the sunlight. They grow hanging onto the branches or tree trunks with aerial roots, not as parasites but as epiphytes. Species of tropical trees native to the Amazon include Brazil nut, rubber tree and Assai palm. The lush flora of the basin is made possible in part by the ten million tonnes of Saharan dust which crosses the Atlantic each year.
Wildlife
Mammals More than 1,400 species of mammals are found in the Amazon, the majority of which are species of bats and rodents. Its larger mammals include the jaguar, ocelot, capybara, puma, South American tapir, White-tailed deer, Amazon river dolphin, and the Amazonian manatee.
Birds
About 1,500 bird species inhabit the Amazon basin. The biodiversity of the Amazon and the sheer number of diverse bird species is given by the number of different bird families that reside in these humid forests. An example of such would be the cotinga family, to which the Guianan cock-of-the-rock belong. Birds such as toucans, and hummingbirds are also found here. Macaws are famous for duck gathering by the hundreds along the clay cliffs of the Amazon River. In the western Amazon hundreds of macaws and other parrots descend to exposed river banks to consume clay on an almost daily basis,Munn, C. A. 1994. Macaws: winged rainbows. National Geographic, 185, 118–140. the exception being rainy days.
Reptiles The green anaconda inhabits the shallow waters of the Amazon and the emerald tree boa and boa constrictor live in the Amazonian tree tops.
Many reptile species are illegally collected and exported for the international pet trade. Live animals are the fourth largest commodity in the smuggling industry after drugs, diamonds and weapons.
Amphibians More than 1,500 species of amphibians swim and are found in the Amazon. Unlike temperate frogs which are mostly limited to habitats near the water, tropical frogs are most abundant in the trees and relatively few are found near bodies of water on the forest floor. The reason for this occurrence is quite simple: frogs must always keep their skin moist since almost half of their respiration is carried out through their skin. The high humidity of the rainforest and frequent rainstorms gives tropical frogs infinitely more freedom to move into the trees and escape the many predators of rainforest waters. The differences between temperate and tropical frogs extend beyond their habitat.
Fish
About 2,500 fish species are known from the Amazon basin and it is estimated that more than 1,000 additional undescribed species exist. This is more than any other river basin on Earth, and Amazonia is the center of diversity for Neotropical fishes. About 45% (more than 1,000 species) of the known Amazonian fish species are endemic to the basin. The remarkable species richness can in part be explained by the large differences between the various parts of the Amazon basin, resulting in many fish species that are endemic to small regions. For example, fauna in clearwater rivers differs from fauna in white and blackwater rivers, fauna in slow moving sections show distinct differences compared to that in rapids, fauna in small streams differ from that in major rivers, and fauna in shallow sections show distinct differences compared to that in deep parts.Mendonça, F. P., W. E. Magnusson, J. Zuanon and C. M. Taylor. (2005) Relationships between habitat characteristics and fish assemblages in small streams of Central Amazonia. Copeia 2005(4): 751–764Duncan, W.P.; and Fernandes, M.N. (2010). Physicochemical characterization of the white, black, and clearwater rivers of the Amazon Basin and its implications on the distribution of freshwater stingrays (Chondrichthyes, Potamotrygonidae). PanamJAS 5(3): 454–464. By far the most diverse orders in the Amazon are Characiformes (43% of total fish species in the Amazon) and Siluriformes (39%), but other groups with many species include Cichlidae (6%) and Gymnotiformes (3%).
In addition to major differences in behavior and ecology, Amazonian fish vary extensively in form and size. The largest, the arapaima and piraiba can reach or more in length and up to in weight, making them some of the largest strict freshwater fish in the world. The bull shark and common sawfish, which have been recorded far up the Amazon, may reach even greater sizes, but they are euryhaline and often seen in marine waters. In contrast to the giants, there are Amazonian fish from several families that are less than long. The smallest are likely the Leptophilypnion sleeper gobies, which do not surpass and are among the smallest fish in the world. Although the true danger they represent often is greatly exaggerated, the Amazon basin is home to several feared fish species such as piranhas (including the famous red-bellied), electric eel, river stingrays and candiru.
Several cavefish species in the genus Phreatobius are found in the Amazon, as is the cave-dwelling Astroblepus pholeter in the far western part of the basin (Andean region). The Tocantins basin, arguably not part of the Amazon basin, has several other cavefish species. The deeper part of the major Amazonian rivers are always dark and a few species have adaptions similar to cavefish (reduced pigment and eyes). Among these are the knifefish Compsaraia and Orthosternarchus, some Cetopsis whale catfish (especially C. oliveirai), some Xyliphius and Micromyzon banjo catfish, and the loricariid catfish Loricaria spinulifera, L. pumila, Peckoltia pankimpuju, Panaque bathyphilus and Panaqolus nix (these five also occur in "normal" forms of shallower waters). The perhaps most unusual habitat used by Amazonian fish is land. The splash tetra is famous for laying its eggs on plants above water, keeping them moist by continuously splashing on them, the South American lungfish can survive underground in a mucous cocoon during the dry season, some small rivulid killifish can jump over land between water sources (sometimes moving relatively long distances, even uphill) and may deliberately jump onto land to escape aquatic predators, and an undescribed species of worm-like Phreatobius catfish lives in waterlogged leaf litter near (not in) streams.
Some of the major fish groups of the Amazon basin include: Order Gymnotiformes: Neotropical electric fishes Order Characiformes: characins, tetras and relatives Family Potamotrygonidae: river stingrays Family Arapaimidae: bonytongues Family Loricariidae: suckermouth catfishes Family Callichthyidae: armored catfishes Family Pimelodidae: pimelodid catfishes Family Trichomycteridae: pencil catfishes Family Auchenipteridae: driftwood catfishes Subfamily Cichlinae: pike cichlids, peacock cichlids and relatives Subfamily Geophaginae: Eartheaters and Neotropical dwarf cichlid Subfamily Poeciliinae: guppies and relatives
Insects
More than 90% of the animal species in the Amazon are insects, of which about 40% are beetles (Coleoptera constituting almost 25% of all known types of animal life-forms.)Powell (2009)
Whereas all of Europe has some 321 butterfly species, the Manú National Park in Peru (4,000 hectare-survey) has 2,300 species, while Tambopata National Reserve (5,500 hectare-survey) has at least 1,231 species.
Climate
The Amazon River basin has a low-water season, and a wet season during which, the rivers flood the adjacent, low-lying forests. The climate of the basin is generally hot and humid. In some areas, however, the summer months (June–September) can bring cold snaps, fueled by Antarctic winds traveling along the adjacent mountain range. The average annual temperature is around 25-degree and 28 degree Celsius with little to no distinction between summer and winter season.
Human lifestyle