AMAZON RIVER SYSTEM
DR. S. M. ALAM
Nov 21 - 27, 2011
The Amazon River in South America is the second longest river in the world after the Nile. It is about 3,912 miles (6,296 km) long and runs from the Andes Mountains in Peru through Brazil to the Atlantic Ocean. It contains more water than any other river in the world-more than the Mississippi, the Nile, and the Yangtze combined.
In one second, the Amazon pours more than 55 million gallons, or 600,000 cubic meters of water, into the Atlantic Ocean, which dilutes the ocean's saltiness for 100 miles from shore. This river forms one of the world's most important river systems.
The Amazon River makes up for 1/5 of the earth's fresh water. The most distant source of the Amazon was established in 1996, as a glacial stream on a snowcapped 5,597 m (18,363 ft) peak called Nevado Mismi in the Peruvian Andes, roughly 160 km (99 mi) west of Lake Titicaca and 700 km (430 mi) southeast of Lima.
The Amazon, which has the largest drainage basin in the world, about 7,050,000 square kilometers (2,720,000 sq mi), accounts for approximately one-fifth of the world's total river flow. The width of the Amazon varies between 1.6 and 10 kilometers (1.0 and 6.2 mi) at low stage, but expands during the wet season to 48 kilometers (30 mi) or more.
The river enters the Atlantic Ocean in a broad estuary about 240 kilometers (150 mi) wide. The mouth of the main stem is 80 kilometers (50 mi). The Amazon River and its tributaries are characterized by extensive forested areas that become flooded every rainy season. Every year the river rises more than nine meters (30 ft), flooding the surrounding forests, known as "flooded forests".
The Amazon's flooded forests are the most extensive example of this habitat type in the world. In an average dry season, 110,000 square kilometers (42,000 sq mi) of land are water-covered, while in the wet season, the flooded area of the Amazon Basin rises to 350,000 square kilometers (140,000 sq mi).
The quantity of water released by the Amazon to the Atlantic Ocean is enormous: up to 300,000 cubic meters per second (11,000,000 cu ft/s) in the rainy season with an average of 209,000 cubic meters per second (7,400,000 cu ft/s) from 1973 to 1990.
The Amazon is responsible for about 20 per cent of the Earth's freshwater entering the ocean. The river pushes a vast plume of freshwater into the ocean. The plume is about 400 kilometers (250 mi) long and between 100 and 200 kilometers (62 and 120 mi) wide.
The freshwater, being lighter, overrides the salty ocean, diluting the salinity and altering the color of the ocean surface over an area up to 1,000,000 square miles (2,600,000 km2) large.
The Atlantic has sufficient wave and tidal energy to carry most of the Amazon's sediments out to sea, thus the Amazon does not form a true delta. The great deltas of the world are all in relatively protected bodies of water while the Amazon empties directly into the turbulent Atlantic.
The tidal bore is the reason the Amazon does not have a protruding delta; the ocean rapidly carries away the vast volume of silt carried by the Amazon, making it impossible for a delta to grow past the shoreline.
The river systems and flood plains in Brazil, Peru, Ecuador, Colombia, and Venezuela are called the "Upper Amazon".
The Amazon River proper runs mostly through Brazil and Peru, it is part of the border between Colombia and Peru and it has tributaries reaching into Venezuela, Colombia, Ecuador, Bolivia and Guyana.
The Amazon rainforest has been described as the "Lungs of our Planet" because it provides the essential environmental world service of continuously recycling carbon dioxide into oxygen. More than 20 percent of the world oxygen is produced in the Amazon Rainforest.
More than half of the world's estimated 10 million species of plants, animals, and insects live in the tropical rainforests. One-fifth of the world's fresh water is in the Amazon Basin.
One hectare (2.47 acres) may contain over 750 types of trees and 1500 species of higher plants. At least 80 per cent of the developed world's diet originates in the tropical rainforest.
Its bountiful gifts for the world include fruits like avocados, coconuts, figs, oranges, lemons, grapefruit, bananas, guavas, pineapples, mangoes and tomatoes; vegetables such as corn, potatoes, rice, winter squash and yams; spices like black pepper, cayenne, chocolate, cinnamon, cloves, ginger, sugarcane, turmeric, coffee and vanilla; and nuts including Brazil nuts and cashews.
At least 3000 fruits are found in the rainforests; of these only 200 are now in use in the western world. Rainforest plants are rich in secondary metabolites, particularly alkaloids.
Biochemists believe alkaloids protect plants from disease and insect attacks. Many alkaloids from higher plants have proven to be of medicinal value and benefit. Currently, 121 prescription drugs sold worldwide come from plant-derived sources. And, while 25 per cent of western pharmaceuticals are derived from rainforest ingredients, less than one per cent of these tropical trees and plants have been tested by scientists.
The U.S. National Cancer Institute has identified 3000 plants that are active against cancer cells and 70 per cent of these plants are found in the rainforest. In 1983, there were no U.S. pharmaceutical manufacturers involved in research programs to discover new drugs or cures from plants. Today, over 100 pharmaceutical companies and several branches of the US government, including giants like Merck are engaged in plant research projects for possible drugs and cures for viruses, infections, cancer and even AIDS.
The Amazon rainforest covers over 1.2 billion acres representing two-fifths of the enormous South American continent and is found in nine South American countries: Brazil, Columbia, Peru, Venezuela, Ecuador, Bolivia, and the three Guyanas.
With 2.5 million square miles of rainforest, the Amazon rainforest represents 54 per cent of the total rainforests left on the planet.
The life force of the Amazon rainforest is the mighty Amazon River. It starts as a trickle high in the snow-capped Andes mountains and flows over 4,000 miles across the South American continent until it enters the Atlantic Ocean at Belem, Brazil where it is 200 to 300 miles across, depending on the season. The Amazon River flows through the center of the rainforest and is fed by 1,100 tributaries.
The rich diversity of plant species in the Amazon rainforest is the highest on earth. Experts show that one hectare (2.47 acres) may contain over 750 types of trees and 1500 species of higher plants and it is estimated that one hectare of Amazon rainforest contains about 900 tons of living plants. Altogether, it contains the largest collection of living plants and animal species in the world. The Andean mountain range and the Amazon jungle are home to more than half of the world's species of flora and fauna and one in five of all the birds in the world live in the rainforests of the Amazon.
To date, some 438,000 species of plants of economic and social interest have been registered in the region and many more have yet been cataloged or even discovered. Today, more than 20 per cent of rainforest in the Amazon has been razed and is gone forever.