Amazon basin

This article is about the drainage basin. For the geologic feature, see Amazon Basin (sedimentary basin).

Amazon River Basin (the southern Guianas, not marked on this map, are part of the basin)

The mouth of the Amazon River

The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about 7,500,000 km² (2,900,000 sq mi), or roughly 40 percent of the South American continent. It is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname and Venezuela.

Most of the basin is covered by the Amazon Rainforest, also known as Amazonia. With a 5,500,000 km² (2,100,000 sq mi) area of dense tropical forest, this is the largest rainforest in the world.

Geography

The Amazon basin is bounded by the Guiana Highlands to the north and the Brazilian Highlands to the south. The Amazon River rises in the Andes Mountains at the west of the basin with its main tributary the Marañón River in Peru. It is usually considered to be the second longest river in the world. However, a team of Brazilian scientists has claimed that the Amazon is the longest river in the world. It covers about 6,400 km before draining into the Atlantic Ocean. The Amazon and its tributaries form the largest volume of water. The Amazon accounts for about 20% of the total water carried to the oceans by rivers. Some of the Amazon rainforest is deforested because of the increasing of cattle ranches and soy beans field.

The highest point in the watershed of the Amazon is the peak of Yerupajá at 6,635 m (21,768 ft).

The Amazon basin formerly flowed west to Pacific Ocean until the Andes formed, causing the basin to flow eastward towards the Atlantic Ocean.

Politically the basin is divided into the Brazilian Amazônia Legal, the Peruvian Amazon, the Amazon region of Colombia and parts of Bolivia, Ecuador and the Venezuelan state of Amazonas.

Plant life

Main article: Amazon rainforest

Aerial view of part of the Amazon rainforest.

As much of the Amazon is unexplored, many of its indigenous plants animals and insects are unknown. Plant growth is dense and its variety of animal inhabitants is comparatively high due to the heavy rainfall and the dense and extensive evergreen and coniferous forests. The sunlight can not reach the ground because of the dense roof created by plants. The ground remains dark and damp and only shade tolerant trees and 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. The most known species of tropical fruit tree that are native to the Amazon are Brazil nut, Cocoa, Rubber tree, Assai palm. The Amazon basin contains thousands of plant species. The bromeliads are special in that they hold water, and frogs may use these plants to hatch their eggs, besides many other living organisms that have their homes in them.The kapok tree is the biggest tree of the Amazon rainforest, as it can grow to 200 feet tall and the trunk can be 10 or 11 feet in diameter and it grows on Varzea, which represents only about 10% of the entire basin. Most of the large Kapok trees have been cut and used as buoy to transport the valuable species of hardwood trees.

Animal life

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 and South American tapir.

Birds

Main article: Birds of the Amazon

About 1500 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 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, 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 reptiles 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 1,000 species of amphibians swim and are found in the Amazon. Unlike temperate frogs which are mostly limited to habitats near 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 in 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.

Red-bellied piranha (Pygocentrus nattereri) is a species of piranha. This species lives in the Amazon River basin, coastal rivers of northeastern Brazil, and the basins of the Paraguay, Paraná and Essequibo Rivers.

Fish

With more than 2,200 species the Amazon basin has a larger fish fauna than any other river basin on Earth, and Amazonia is the center of diversity for Neotropical fishes. The Amazon basin is home to the red-bellied piranha, an omnivorous forager that encompasses a larger geographic area than any other piranha species. 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.

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

See also: List of butterflies of the Amazon River basin and the Andes

Over 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).

Whereas all of Europe has some 321 butterfly species, the Manú National Park in Peru (4000 hectare-survey) has 1300 species, while Tambopata National Reserve (5500 hectare-survey) has at least 1231 species.

Climate and seasons

The Amazon River basin has a low-water season, and a wet season during which the rivers flood adjacent low lying forests. The climate of the basin is generally hot and humid. In some areas, however, the winter months (June–September) can bring cold snaps, fueled by Antarctic winds travelling along the adjacent Andes mountain range. Such cold conditions can be devastating for some of the region's tropical plant and animal species.

Human occupation

A floating village in Iquitos, Peru

Amazonia is sparsely 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 in Iquitos, Peru, and Manaus and Belém (Brazil). In many regions, the forest has been cleared for soya bean plantations and ranching (the most extensive non-forest use of the land); some of the inhabitants harvest wild rubber latex, and Brazil 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 largest organization fighting for the indigenous peoples in this area is COICA. It is a supra organization encompassing all indigenous rights organizations working in the Amazon basin area, and covers the people living in several countries.

River commerce

The river is the principal path of transportation for people and produce in the regions, with transport ranging from balsa rafts and dugout canoes to hand built wooden river craft and modern steel hulled craft.

Agriculture

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 additional slash and burn agriculture on higher floodplains. Fishing provides additional food year round, and free-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 of bush meat, particularly deer and turtles is common.

Deforestationand increased road-building bring human encroachment upon wild areas, increased resource extraction and threats to biodiversity.

Extensive deforestation, particularly in Brazil, is leading to the extinction of known and unknown species, reducing biological 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.

Languages

The most widely spoken language in the Amazon is Portuguese, followed closely by Spanish. On the Brazilian side Portuguese is spoken by at least 98% of the population, whilst in the Spanish-speaking countries a large number of speakers of indigenous languages are present, though Spanish is predominant.

There are hundreds of native languages still spoken in the Amazon, most of which are spoken by only a handful of people, and thus are critically endangered. One of the more widely spoken indigenous languages in the Amazon is Nheengatu, which descends from the ancient Tupi language, originally spoken in the coastal and central regions of Brazil. It was brought to its present location along the Rio Negro by Brazilian colonizers who, until the mid-17th century, primarily used Tupi rather than the official Portuguese to communicate. Besides modern Nheengatu, other languages of the Tupi family are spoken there, along with other language families like Jê, Arawak, Karib, Arawá, Yanomamo, Matsés and others.

See also

• Amazon Conservation Association
• Deforestation of the Amazon rainforest
• Panthera onca onca
• Peruvian jaguar
• Southern jaguar
• Ucayali Peneplain

External links

• Herndon and Gibbon Lieutenants United States Navy The First North American Explorers of the Amazon Valley, by Historian Normand E. Klare. Actual Reports from the explorers are compared with present Amazon basin conditions.
• Scientists find Evidence Discrediting Theory Amazon was Virtually Unlivable by The Washington Post
• "The Course of the River of the Amazons, Based on the Account of Christopher d’Acugna" from 1680