The Amazon Biome, is defined as the area covered predominantly by dense moist tropical forest, with relatively small inclusions of several other types of vegetation such as savannas, floodplain forests, grasslands, swamps, bamboos, and palm forests. The biome encompasses 6.7 million km2 and is shared by eight countries (Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, Guyana and Suriname), as well as the overseas territory of French Guiana. The complete watersheds expand beyond the biome and sometimes include adjacent biomes (dry forest, cerrado and puna).
Not just green wilderness
So is the Amazon River Basin
merely a huge, uniform expanse of rainforest, bisected by a massive river? Such a perception of the area merely scratches the surface of what is in reality a highly complex and dynamic environment. The basin actually encompasses a variety of landscapes and ecosystems
. These include:
How the Earth's movements created today's Amazon River Basin
Millions of years ago, the Amazon River
once flowed from east to west, emptying into the Pacific Ocean. When the Andes Mountains began to rise (due to great pressure on the tectonic plates) along the eastern side of the South American continent about 20 million years ago6
, this emerging mass blocked the flow of the Amazon River.
Freshwater lakes formed as a result, and the flow of the river gradually reversed to its current eastern course. About 10 million years ago, the river reached the Atlantic Ocean, close to the city of Belem in Brazil.7
The water cycle: a highly efficient natural process
Every year, the Amazon rainforest receives torrential rainfall - between 1,500 mm and 3,000 mm.9
Where does all that water come from?
Eastern trade winds that blow from the Atlantic Ocean account for about half of the rainfall, with the other half due to evapotranspiration - the loss of water from the soil by evaporation and through transpiration from plants10
- in the Amazon River Basin.11
If evapotranspiration and its role in maintaining ecological balance is disrupted, the climate throughout region - and well beyond - will be significantly impacted.