The Amazon basin is the largest watershed on Earth. It provides about 20 percent of all fresh water flowing from continents into the oceans, and discharges more water per second than the Mississippi, the Nile and the Yangtze combined. During peak flood season, between May and July, freshwater from the Amazon can be detected more than 150 km miles out to sea.
Just how big is Amazonia? That depends on whether you draw the boundaries based on hydrography, tropical forests or the political boundaries drawn by the nine countries that share the watershed (Bolivia, Brazil, Colombia, Ecuador,French Guiana, Guyana, Peru, Suriname and Venezuela). Depending on the criteria used, the area ranges from 5,147,970 to 8,187,965 square kilometers, about one-fifth of which is in conservation areas.
Its varying topography, soil structure, rainfall patterns and seasonal flooding make Amazonia an area of enormous biological diversity. The region contains about half the world’s tropical forests, with nearly 40,000 plant species and a great diversity of birds, butterflies and freshwater fish. The Amazon region also demonstrates that biological and cultural diversity often go hand in hand. The region is home to some 420 indigenous groups speaking 86 languages. An estimated 60 groups live in what has become known as “voluntary isolation,” maintaining a traditional nomadic lifestyle, shunning contact with the outside world. Many of those groups live near the border between Brazil and its neighbors to the west.