TheAmazon basin is the part ofSouth America drained by theAmazon River and itstributaries. The Amazondrainage basin covers an area of about 7,000,000 km2 (2,700,000 sq mi),[1] or about 35.5 percent of the South American continent. It is located in the countries ofBolivia,Brazil,Colombia,Ecuador,Guyana,Peru,Suriname, andVenezuela, as well as the territory ofFrench Guiana.[2][3]
Most of the basin is covered by theAmazon rainforest, also known asAmazonia. With a 6 million km2 (2.3 million sq mi)[4] area of densetropical forest, it is the largestrainforest in the world.
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The Amazon River begins in theAndes Mountains at the west of the basin with its main tributary theMarañón River andApurimac River inPeru. The highest point in thewatershed of the Amazon is the second biggest peak ofYerupajá at 6,635 metres (21,768 ft).
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 6,400 km (4,000 mi) before it drains into theAtlantic Ocean, it isone of the two longest rivers in the world. A team of scientists has claimed that the Amazon is longer than theNile,[5] but debate about its exact length continues.[6]
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 theAmazon rainforests aredeforested because of an increase in cattle ranches and soybean fields. The Amazon basin formerly flowed west to thePacific Ocean until the Andes formed, causing the basin to flow eastward towards the Atlantic Ocean.[7]
Politically the basin is divided intoPeruvian Amazonia,Amazônia Legal of Brazil, theAmazon natural region ofColombia,Amazonas (Venezuelan state), and parts ofBolivia andEcuador.
| Country | State | Area (km2) | (%) | Discharge (km3) | (%) |
|---|---|---|---|---|---|
 Bolivia | 724,000 | 10.4 | 291 | 4.0 | |
 Brazil | 4,674,619 | 67.5 | 4,167.3 | 57.2 | |
 Acre | 164,123 | 3.5 | 144.2 | 2.0 | |
 Amapá | 44,870 | 1.0 | 57.7 | 0.8 | |
 Amazonas | 1,559,159 | 33.3 | 1,848.3 | 25.4 | |
.svg) Brasília | 1,010 | 0.02 | |||
 Goiás | 212,131 | 4.5 | 96.7 | 1.3 | |
 Maranhão | 39,396 | 0.8 | 9.4 | 0.1 | |
 Mato Grosso | 723,470 | 15.5 | 490.6 | 6.7 | |
 Pará | 1,190,147 | 25.5 | 1,053.1 | 14.5 | |
 Rondônia | 237,591 | 5.08 | 140.6 | 1.9 | |
 Roraima | 224,301 | 4.8 | 211.6 | 2.9 | |
 Tocantins | 278,421 | 6.0 | 115.1 | 1.6 | |
 Ecuador | 146,688 | 2.1 | 258.4 | 3.6 | |
 Guyana | 12,224 | 0.2 | 8.8 | 0.1 | |
 Colombia | 345,293 | 5.0 | 755 | 10.4 | |
 Peru | 967,176 | 14.0 | 1,739.5 | 23.9 | |
 Venezuela | 53,000 | 0.8 | 60.0 | 0.8 | |
| Amazon basin | 6,923,000 | 100.0 | 7,280 | 100.0 | |
Plant growth is quite dense and its variety of animal inhabitants is comparatively high due to the heavy rainfall and the dense and extensiveevergreen andconiferous forests. Littlesunlight 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 andbromeliads exploit trees and other plants to get closer to the sunlight. They grow hanging onto the branches or tree trunks withaerial roots, not as parasites but asepiphytes. Species of tropical trees native to the Amazon includeBrazil nut,rubber tree andAssai palm.[10][11]The lush flora of the basin is made possible in part by the ten million tonnes ofSaharan dust which crosses theAtlantic each year.[12]
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More than 1,400 species ofmammals are found in the Amazon, the majority of which are species ofbats androdents. Its larger mammals include thejaguar,ocelot,capybara,puma andSouth American tapirWhite Tailed Deer
About 1,500bird species inhabit the Amazon basin.[13] Thebiodiversity 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 thecotinga family, to which theGuianan cock-of-the-rock belong. Birds such astoucans, andhummingbirds 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 ofmacaws and otherparrots descend to exposed river banks to consume clay on an almost daily basis,[14] the exception being rainy days.[15]
Thegreen anaconda inhabits the shallow waters of the Amazon and theemerald tree boa andboa constrictor live in the Amazonian tree tops.
Manyreptile 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.[16]
More than 1,500 species ofamphibians swim and are found in the Amazon. Unlike temperatefrogs which are mostly limited tohabitats near the water, tropical frogs are most abundant in the trees and relatively few are found near bodies of water on theforest floor. The reason for this occurrence is quite simple: frogs must always keep theirskin moist since almost half of theirrespiration is carried out through their skin. The highhumidity of the rainforest and frequentrainstorms gives tropical frogs infinitely more freedom to move into the trees and escape the manypredators of rainforest waters. The differences between temperate and tropical frogs extend beyond their habitat.[citation needed]
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About 2,500fish species are known from the Amazon basin and it is estimated that more than 1,000 additionalundescribed species exist.[17] This is more than any other river basin on Earth, and Amazonia is the center of diversity forNeotropical fishes.[18] About 45% (more than 1,000 species) of the known Amazonian fish species areendemic to the basin.[19] 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 inclearwater rivers differs from fauna inwhite andblackwater rivers, fauna in slow moving sections show distinct differences compared to that inrapids, fauna in small streams differ from that in major rivers, and fauna in shallow sections show distinct differences compared to that in deep parts.[20][21][22] By far the most diverse orders in the Amazon areCharaciformes (43% of total fish species in the Amazon) andSiluriformes (39%), but other groups with many species includeCichlidae (6%) andGymnotiformes (3%).[17]
In addition to major differences in behavior and ecology, Amazonian fish vary extensively in form and size. The largest, thearapaima andpiraiba can reach 3 m (9.8 ft) or more in length and up to 200 kg (440 lb) in weight, making them some of thelargest strict freshwater fish in the world.[23][24] Thebull shark andcommon sawfish, which have been recorded far up the Amazon, may reach even greater sizes, but they areeuryhaline and often seen in marine waters.[25][26] In contrast to the giants, there are Amazonian fish from several families that are less than 2 cm (0.8 in) long. The smallest are likely theLeptophilypnion sleeper gobies, which do not surpass 1 cm (0.4 in) and are among thesmallest fish in the world.[27]
The Amazon supports very large fisheries, including well-known species of large catfish (such asBrachyplatystoma, which perform long breedingmigrations up the Amazon),arapaima andtambaqui, and is also home to many species that are important in theaquarium trade, such as theoscar,discus,angelfish,Corydoras catfish andneon tetra.[17] Although the true danger they represent often is greatly exaggerated, the Amazon basin is home to several feared fish species such aspiranhas (including the famousred-bellied),electric eel,river stingrays andcandiru.[28]
Severalcavefish species in the genusPhreatobius are found in the Amazon, as is the cave-dwellingAstroblepus pholeter in the far western part of the basin (Andean region).[29] TheTocantins basin, arguably not part of the Amazon basin, has several other cavefish species.[29] 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 knifefishCompsaraia andOrthosternarchus, someCetopsis whale catfish (especiallyC. oliveirai), someXyliphius andMicromyzon banjo catfish,[30] and the loricariid catfishLoricaria spinulifera,L. pumila,Peckoltia pankimpuju,Panaque bathyphilus andPanaqolus nix (these five also occur in "normal" forms of shallower waters).[31][32][33] The perhaps most unusual habitat used by Amazonian fish is land. Thesplash tetra is famous for laying its eggs on plants above water, keeping them moist by continuously splashing on them,[34] theSouth American lungfish can survive underground in a mucous cocoon during the dry season,[35] some smallrivulid 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,[36][37] and anundescribed species of worm-likePhreatobius catfish lives in waterloggedleaf litter near (not in) streams.[38][39]
Some of the major fish groups of the Amazon basin include:[28]
More than 90% of the animal species in the Amazon areinsects,[40] of which about 40% arebeetles (Coleoptera constituting almost 25% of all known types of animal life-forms.)[41][42][43]
Whereas all of Europe has some 321butterfly species, theManú National Park in Peru (4,000 hectare-survey) has 2,300 species, whileTambopata National Reserve (5,500 hectare-survey) has at least 1,231 species.
TheAmazon River basin has a low-water season (known popularly as summer), and a wet season (known popularly as winter) during which, the riversflood the adjacent, low-lying forests. Theclimate of the basin isgenerally 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.
Amazonia issparsely populated. There are scattered settlements inland, but most of the population lives in a few larger cities on the banks of the Amazon and other major rivers, such as inIquitos –Loreto inPeru,Manaus-Amazonas State, andBelém,Pará. In many regions, the forest has been cleared forsoya beanplantations andranching (the most extensive non-forest use of the land); some of the inhabitants harvest wildrubberlatex, andBrazilian nuts. This is a form of extractive farms, where the trees are not cut down. These are relatively sustainable operations in contrast to lumbering or agriculture dependent on clearing the rainforest. The people live in thatched houses shaped liked beehives. They also build apartment-like houses called "Maloca", with a steeply slanting roof.
The most widely spoken languages in the Amazon arePortuguese andSpanish. There are hundreds ofnative languages still spoken in the Amazon, most of which are criticallyendangered.
Many tribal groups live in the Amazon Basin, often in relative isolation. It is estimated 400 or more tribal groups have lived in the Amazon Basin for hundreds of years with their own culture, language, and lifestyle. Today total population of Amazon basin is 1.5 million distributed. There are an estimated 100 uncontacted tribal groups.The largest organization fighting for theindigenous peoples in this area isCOICA. It is a supra organization encompassing allindigenous rights organizations working in the Amazon basin area, and covers the people living in several countries.
The river is the principal path of transportation for people and produce in the regions, with transport ranging from balsarafts anddugout canoes to hand built wooden river craft andmodern steel hulled craft.
Seasonal floods excavate and redistribute nutrient-rich silt onto beaches and islands, enabling dry-season riverside agriculture of rice, beans, and corn on the river's shoreline without the addition of fertilizer, with additionalslash and burn agriculture on higher floodplains. Fishing provides additional food year-round, andfree-range chickens need little or no food beyond what they can forage locally.Charcoal made largely from forest and shoreline deadfall is produced for use in urban areas. Exploitation ofbushmeat, particularlydeer andturtles is common.
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Extensivedeforestation, particularly inBrazil, is leading to theextinction of known and unknown species, reducingbiological diversity and adversely impacting soil, water, and air quality. A final part of the deforestation process is the large-scale production of charcoal for industrial processes such as steel manufacturing. Soils within the region are generally shallow and cannot be used for more than a few seasons without the addition of imported fertilizers and chemicals.
"Over past 20 years (2021), the Brazilian Amazon emitted 13% more CO2 than it absorbed".[44][45]
Amazon vegetation holds around 56.8 billion metric tons of carbon above ground. The slash and burn cycle is causing the Amazon to release more carbon than it takes in.[46]
The Amazon Basin holds 10% of the world's biodiversity and about 15% of the worlds river discharge. The Amazon functions as a carbon sink due tophotosynthesis where carbon dioxide is converted into oxygen. The role the vegetation plays in thewater cycle is very important. 50% to 80% of the water remains locked within the basin due to the complex role vegetation, rivers and the atmosphere play with each other. Without trees the Amazon Basin's ability to hold onto the water will disappear and will lead toDesertification.[47]
"Amazon biodiversity also plays a critical role as part of global systems, influencing the globalcarbon cycle and thusclimate change, as well as hemispheric hydrological systems, serving as an important anchor for South American climate and rainfall. It also produces 20% oxygen of the Earth."[48]
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