Amazonian Rainforest 

East of the Andes, the Amazon Rainforest begins. It is the largest rainforest in the world and is of great ecological significance, as its biomass is capable of absorbing enormous amounts of carbon dioxide. Conservation of the Amazon Rainforest has been a major issue in recent years. 

The rainforest is supported by the extremely wet climate of the Amazon basin. The Amazon, and its hundreds of tributaries, flow slowly across the landscape, with an extremely shallow gradient sending them towards the sea: Manaus, 1,600 km (1,000 mi) from the Atlantic, is only 44 m (144 ft) above sea level. 

The biodiversity within the rainforest is extraordinary: the region is home to at least 2.5 million insect species, tens of thousands of plants, and some 2,000 birds and mammals. One fifth of all the world's species of birds can be found in the Amazon rainforest. 

The diversity of plant species in the Amazon basin is the highest on Earth. Some experts estimate that one square kilometer may contain over 75,000 types of trees and 150,000 species of higher plants. One square kilometer of Amazon rainforest can contain about 90,000 tons of living plants. 

Exploitation 

The Solimões and Negro rivers join near Manaus. The Solimões is laden with silt carried down from the Andes; the clear-running Negro has its source in a region with little sediment. For 350 years after the European discovery of the Amazon by Pinzon, the Portuguese portion of its basin remained an almost undisturbed wilderness, occupied by indigenous tribes split into countless fragments by their quest for food. Because of the difficulty of hunting and gathering food, the indigenous inhabitants probably had a population density no higher than one person to every 13 km² (5 sq. miles) of territory. 

A few settlements on the banks of the main river and some of its tributaries had been founded by the Portuguese either for trade with the Indians or for evangelizing purposes. The total population of the Brazilian portion of the Amazon basin in 1850 was perhaps 300,000, of whom about two-thirds comprised by Europeans and slaves, the slaves amounting to about 25,000. 

The principal commercial city, Para, had from 10,000 to 12,000 inhabitants, including slaves. The town of Manáos, now Manaus, at the mouth of the Rio Negro, had from 1,000 to 1,500 people. All the remaining villages, as far up as Tabatinga, on the Brazilian frontier of Peru, were very small. 

On September 6, 1850, the emperor, Dom Pedro II, sanctioned a law authorizing steam navigation on the Amazon, and gave Barao Maua (Irineu Evangilista de Sousa) the task of putting it into effect. He organized the "Compania de Navigacao e Commercio do Amazonas" at Rio de Janeiro in 1852; and in the following year it commenced operations with three small steamers, the Monarch, the Marajo and Rio Negro. 

At first, navigation was principally confined to the main river; and even in 1857 a modification of the government contract only obliged the company to a monthly service between Para and Manáos, with steamers of 200 tons cargo capacity, a second line to make six round voyages a year between Manaós and Tabatinga, and a third, two trips a month between Para and Cameta. This was the first step in opening up the vast interior. 

The success of the venture called attention to the opportunities for economic exploitation of the Amazon, and a second company soon opened commerce on the Madeira, Purus and Negro; a third established a line between Para and Manáos; and a fourth found it profitable to navigate some of the smaller streams. In that same period, the Amazonas Company was increasing its fleet. Meanwhile, private individuals were building and running small steam craft of their own on the main river as well as on many of its tributaries. 

On July 31, 1867 the government of Brazil, constantly pressed by the maritime powers and by the countries encircling the upper Amazon basin, decreed the opening of the Amazon to all flags; but limited this to certain defined points: Tabatinga—on the Amazon; Cameta—on the Tocantins; Santarem—on the Tapajos; Borba—on the Madeira and Manáos—on the Rio Negro. The decree took effect on September 7, 1867. 

Manáos (now Manaus), Para and Iquitos are now thriving commercial centers. The first direct foreign trade with Manáos was commenced about 1874. The local trade of the river was carried on by the English successors to the Amazonas Company—the Amazon Steam Navigation Company—as well as numerous small river steamers, belonging to companies and firms engaged in the rubber trade, navigating the Negro, Madeira, Purfis and many other streams. The principal exports of the valley were India rubber, cacao, Brazil nuts and a few other products of very minor importance. 

20th Century Concerns 

Four centuries after the discovery of the Amazon river, the total cultivated area in its basin was probably less than 25 square miles (65 km²), excluding the limited and rudely cultivated areas among the mountains at its extreme headwaters. This situation changed dramatically during the 20th century. 

The construction of the new capital Brasilia in the interior in 1960 also contributed to the opening up of the Amazon basin. A large-scale colonization program saw families from northeastern Brazil relocated to the forests, encouraged by promises of cheap land. Many settlements grew along the road from Brasilia to Belem, but rainforest soil proved difficult to cultivate. 

Still, long-term development plans continued. Roads were cut through the forests, and in 1970, the work on Trans-Amazon highway network began. The network's three pioneering highways were completed within ten years, connecting all the major cities of the Brazilian Amazon interior. 

Cattle farming became a major impetus in deforestation, with military governments in the 1960s and 1970s heavily subsidizing the creation of large ranches. By the 1980s the rate of destruction of the rainforest was dizzying, and it is estimated that over a fifth of the total area of the rainforest has now been clear-cut. The preservation of the remaining forest is becoming an ever more prominent concern.

Wildlife 

The waters of the Amazon support a diverse range of wildlife. Along with the Orinoco, the river is one of the main habitats of the Boto, also known as the Amazon River Dolphin. The largest species of river dolphin, it can grow to lengths of up to 2.6 m. 

Also present in large numbers are the notorious Piranha, carnivorous fish which congregate in large schools, and may attack livestock and even humans. Although many experts believe their reputation for ferocity is unwarranted, a school of piranha was apparently responsible for the deaths of up to 300 people when their boat capsized near Obidos in 1981. 

The Anaconda snake is found in shallow waters in the Amazon basin. One of the world's largest species of snake, the Anaconda spends most of its time in the water, with just its nostrils above the surface. Anacondas have been known very occasionally to attack fishermen. 

The river also supports thousands of species of fish, as well as crabs and turtles.