Amazon Basin
The Amazon Basin is the huge area of land in South America drained by the Amazon River and its more than 1,100 tributaries. It is the largest river basin on Earth, covering an area roughly the size of Australia and 40% of the entire South American continent. The basin contains the world's biggest rainforest, the planet's largest river by volume, and roughly one in ten of all the species on Earth.
- Areaapprox. 7 million km²About the size of Australia
- Countries9Mostly Brazil, plus 8 others
- Main riverAmazon6,400 km long
- Water volumeapprox. 20% of world riversMost water of any river system
- Speciesapprox. 10% of all on EarthA huge slice of global biodiversity
- Indigenous peopleapprox. 400 groupsSpeaking hundreds of languages
How big is the Amazon Basin compared to other river basins?
The Amazon Basin is the largest river drainage area in the world. Its rivers carry roughly twice as much water as the next six biggest river systems combined.
What is the Amazon Basin?
A river basin is all the land from which water drains into a single river system. The Amazon Basin includes everything that drains into the Amazon River. That means the river itself, its thousand-plus tributaries, the rainforest growing in their floodplains, and the upland areas that feed the streams. The basin spans nine countries: Brazil, Peru, Colombia, Venezuela, Ecuador, Bolivia, Guyana, Suriname and French Guiana, but approx. 60% lies in Brazil.
The biggest river in the world
The Amazon River is the biggest river in the world by water volume by a long way. At its mouth it pours roughly 209,000 cubic metres of water into the Atlantic Ocean every second, around five times more than the Congo (the second biggest). About a fifth of all the fresh water flowing into the world's oceans at any moment is from the Amazon.
The river is so powerful that it pushes a tongue of fresh water out into the Atlantic Ocean. Sailors can drink the water more than 100 km offshore.
Wildlife of the basin
The basin contains approx. 10% of all the species on Earth: jaguars, pink river dolphins, capybaras, sloths, anacondas, electric eels, piranhas, scarlet macaws, harpy eagles, and millions of insects. The river itself holds over 2,500 species of fish (more than in the whole Atlantic Ocean) including the giant arapaima, one of the largest freshwater fish in the world.
People of the basin
People have lived in the Amazon Basin for at least 12,000 years. There are around 400 indigenous groups, speaking hundreds of different languages. Some live in towns alongside non-indigenous Brazilians and Peruvians. Others live deep in the forest, hunting and farming the way their ancestors did. A small number are uncontacted, meaning they have chosen not to make contact with the outside world.
Threats to the basin
The Amazon Basin is under huge pressure. Around 17% of the rainforest has already been cleared, mostly for cattle ranching, soy farming and roads. Scientists worry that if 25% is lost, the basin will stop being able to make enough rain to keep the forest alive. The whole system could then start to collapse into dry savanna, releasing huge amounts of carbon dioxide and disrupting weather across South America.
Deeper dive: the Andes-Amazon connection, blackwater rivers and indigenous land rights
The Amazon Basin starts not in the rainforest but high in the Andes mountains of Peru. Snowmelt and rain on the eastern slopes of the Andes feed thousands of small streams that join up into mighty rivers like the Ucayali and the Marañón, which combine to form the Amazon proper. Around 17% of all the sediment carried by the Amazon River was once part of the Andes mountains, slowly eroded and washed downstream over millions of years. This sediment is what makes the Amazon River brown and fertile.
Many of the Amazon's tributaries, however, are not muddy brown but dark like tea. The Rio Negro (Black River), the Tapajós and several others drain rainforest where the soils are very poor and the rainwater seeps through layers of dead leaves on the way to the rivers. The decomposing leaves release tannins (the same chemicals that colour tea) and the rivers come out a deep clear dark colour. These blackwater rivers have very low nutrients and host fewer fish species than the muddy whitewater rivers from the Andes. The famous "Meeting of the Waters" near Manaus is where the dark Rio Negro joins the muddy Solimões; the two flow side by side for 6 km without mixing because of differences in temperature, speed and density.
The legal protection of the Amazon basin depends heavily on the recognition of indigenous land rights. Indigenous reserves and other protected areas cover roughly half of the Brazilian Amazon, and they have proved to be the most effective barrier against deforestation. Satellite imagery shows that deforestation rates inside indigenous territories are dramatically lower than outside. The 1988 Brazilian Constitution recognised indigenous land rights, but the actual demarcation of territories has often been slow and contested. The election of indigenous leader Sonia Guajajara to head Brazil's new Ministry for Indigenous Peoples in 2023 was a major step in formalising this protection.
The forest itself is described on the Amazon Rainforest page. The main country is Brazil.