The Amazon rainforest, also known as Amazonia, is one of the world's greatest natural resources. Because its vegetation continuously recycles carbon dioxide into oxygen, it has been described as the "Lungs of our Planet". About 20% of earth's oxygen is produced by the Amazon rainforest.
The Amazon rainforest gets its name from the Amazon River, the life force of the rainforest. The Amazon River begins in the Peruvian Andes, and winds its way east over the northern half of South America. It meets the Atlantic Ocean at Belem, Brazil. The main river is about 4,080 miles long. Its drainage basin covers 2,722,000 million square miles, and lies in the countries of Brazil, Columbia, Peru, Venezuela, Ecuador, Bolivia, and the three Guyanas. Sixteen percent of all the world's river water flows through the Amazon delta. Twenty eight billion gallons of water flow into the Atlantic every minute, diluting the salinity of the ocean for more than 100 miles offshore. The Amazon rainforest watershed is home to the world's highest level of biodiversity.
Amazonia receives about 9 feet of rain every year. Fifty percent of this returns to the atmosphere through the foliage of trees. Most of the Amazon River's water comes from the annual snowmelt high in the Peruvian Andes. Between June and October, the water level rises by 30 to 45 feet. Tens of millions of acres of rainforest are covered by water as the flood advances, reaching as far inland from the main channel as 12 miles.
Some 15 million years ago, the Amazon River flowed westward into the Pacific Ocean. When the South American plate moved into another tectonic plate, the Andes Mountains slowly rose up and blocked the flow of the river. As the river system backed up, freshwater lakes were formed, and the environment of the Amazon basin changed drastically. Then about 10 million years ago the river found its way eastward towards the Atlantic.
The Amazon rainforest is the drainage basin for the Amazon River and its many tributaries. The northern half of the South American continent is shaped like a shallow dish. About 1,100 tributaries, seventeen of which are over 1,000 miles long, drain into this depression. Whenever rain falls in the river basin, it all drains into Amazon rainforest and into the Amazon River. The Amazon is the largest river system in the world. At some points, the Amazon River is one mile wide, while at other points it can be thirty-five miles wide. At Belem, where the river flows into the Atlantic Ocean, it can be 200 to 300 miles across, depending on the season. Some of the animals that make their home here are river otters, freshwater river dolphins, turtles, piranha, manatees, electric eels, and a remarkable, giant air-breathing fish called the piraracu.
The world's largest tropical rainforest, Amazonia covers more than half of Brazil. The canopy of Amazonia is less studied than the ocean floor. Scientists believe that the canopy may contain half of the world's species. Over 500 mammals, 175 lizards and over 300 other reptiles species, and one third of the world's birds live in Amazonia. It is estimated that about 30 million insect types can be found here. Competition for survival is fierce. This may explain why over millions of years of evolution so many highly adapted species have evolved in the canopy of Amazonia. The most intense competition is between animals and plants. Both plants and animals have made adaptations to defend themselves from being eaten, and to overcome these defensive systems. Plants trap sunlight and turn it into energy for themselves and the herbivores of the canopy.
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