The Amazon is one of Earth’s two longest rivers. It stretches an incredible 6,800 kilometres (4,225 miles) west to east across South America – the approximate distance between New York and Rome. It’s also the world’s largest river by volume, transporting 20 per cent of the freshwater on Earth and more than the world’s seven next largest rivers combined.
Feeding this gigantic torrent is the rain and snow falling across around 40 per cent of South America. This area is called the Amazon’s drainage basin and is surrounded by three mountain ranges: the Andes to the west, Guiana Highlands to the south and Brazilian Highlands to the north. The Amazon Basin takes its name from the river. It is the world’s largest lowland with an area of around 7 million square kilometres (2.7 million square miles) – almost the size of Australia. At its widest, the basin stretches 2,780 kilometres (1,725 miles) from north to south.
Around 85 per cent of the Amazon Basin is filled with the Amazon rainforest, Earth’s biggest tropical forest. This densely vegetated region contains around half of the world’s remaining rainforest and is sometimes called the ‘lungs of the Earth’. An estimated 20 per cent of Earth’s oxygen is produced by the Amazon’s foliage, which draws in carbon dioxide and releases oxygen via mass-scale photosynthesis.
Rainforests form in the Amazon Basin because of its equatorial climate; it lies within 15 degrees of the equator. Conditions are warm and wet year-round with little difference in weather between seasons. Average temperatures are about 26 degrees Celsius (79 degrees Fahrenheit) and rain falls, on average, 250 days a year.
The steady tropical climate encourages varied fast-growing plants. In just one hectare (2.5 acres) of Amazon rainforest in Ecuador, scientists found an incredible 473 tree species. The tallest trees can reach heights of 46 metres (150 feet) and live for thousands of years. Their huge leafy canopies harvest perhaps 70 per cent of incoming light and 80 per cent of rainfall, preventing it reaching the forest floor. When a tree topples, saplings race upwards to fill the space. Beneath these is a shrub layer and a second forest layer – 20 metres (65 feet) tall, the height of British deciduous trees. When the trees and shrubs die, rapid leaf decay releases nutrients that fuel the ecosystem.
The Amazon Basin teems with life. More than one in ten species live in the Amazon – many found nowhere else. These include around 20 per cent of Earth’s bird species, 370 reptile species, thousands of tree-dwellers, and 7,500 butterfly species compared to about 60 in the UK. Many more species remain undiscovered. An average three new plant and animal species were catalogued each day between 1999 and 2009, according to conservation group WWF. These included a four-metre (13-foot)-long snake, a bald-headed parrot and a blind crimson catfish.
The Amazon is threatened by deforestation and climate change. A future temperature rise of four degrees Celsius (39 degrees Fahrenheit) would see 85 per cent of the forest destroyed by drought within a century. What’s more, in the last 50 years, at least 12 per cent of the trees in this remote wilderness have been cleared for agriculture. Around 80 per cent of these areas are now occupied by cattle ranches and more forest may have been selectively logged. The rainforest is so huge that it produces around 50 per cent of its rainfall by releasing water from its leaves. Cut down enough trees and the remaining rainforest would dry out, and die of drought or forest fire.
The WWF warns the Amazon’s flora stores between 90 and 140 billion tons of carbon. If each dying plant were to release its carbon into the atmosphere, the increase in greenhouse gases would greatly accelerate global warming.
Journey down the Amazon river
The Amazon starts its journey to the Atlantic Ocean in Peru. Its ultimate source is high in the Andes, Earth’s longest mountain range that extends 9,000 kilometres (5,592 miles) along South America’s west coast. From there, it flows eastwards through the lowlands of Colombia, Ecuador, Brazil and Bolivia. Joining it on the way are more than 1,000 tributaries with sources in the Andes, as well as the Brazilian and Guiana Highlands.
The Upper Amazon
The Amazon’s source is on the ice-covered slopes of Nevado Mismi, a 5,597-metre (18,363-foot) mountain in southern Peru. Trickles of snowmelt become hundreds of tiny rivulets, which grow into creeks as they run downhill. Amazingly, no one had pinpointed the Amazon’s origins more accurately than ‘the Andes’ until as short a time ago as the Nineties. Scientists still debate which creek is the Amazon’s true source.
These creeks merge to become the Apurimac River, which cascades through Earth’s third-largest canyon as white-water rapids. The Apurimac joins the Urubamba, which flows beneath the Incan city of Machu Picchu to form the Ucayali. This meanders northwards through thick forests east of the Andes until it joins the Maranon River, southwest of Peruvian port Iquitos. At this junction, the river officially becomes the Amazon.
- Nevado Mismi
- Apurimac Canyon
- Ucayali River
- Machu Picchu
More than 1,000 tributaries flow into the Amazon as it winds from Iquitos 3,700 kilometres (2,300 miles) downhill through the lowland rainforest. The two biggest are the Rio Solimoes and Rio Negro, which join the Amazon downstream of the jungle port of Manaus, 1,600 kilometres (1,000 miles) from the ocean. Sea-going ships can travel upriver to Manaus.
Rio Negro means ‘black river’ because the waters are stained tea brown by decaying forest leaves. This river contains little sediment because it begins on the hard ancient rocks of the Brazilian Highlands.
The 3,380-kilometre (2,100-mile)-long Solimoes, meanwhile, originates in the Andes, which are eroding rapidly. Its waters are yellowed by around 400 million tons of sediment each year, which is equivalent to the annual weight of Britain’s discarded rubbish. When the Solimoes and Negro meet, their different-coloured waters remain unmixed and flow side-by-side for about five kilometres (three miles); this is the Encontro das Aguas.
- Rio Negro
- Madeira/Rio Solimóes
Mouth of the Amazon
The Amazon gushes into the Atlantic via a huge estuary 240 kilometres (150 miles) wide – that’s broader than the English Channel. Here the river drops its sediment as a maze of islands, salt marshes and sandbanks.
The estuary is split into several smaller channels. North of Marajo, an island larger than Denmark, the main river divides into two. A smaller arm of the Amazon runs south of Marajo past the Brazilian port city of Belem.
The estuary has no delta. Ocean currents carry the 1.3 million tons of sediment that the Amazon discharges daily north-west to form an underwater debris cone.
Tides flow up the estuary, changing river levels perhaps 970 kilometres (600 miles) from the ocean. Before spring tides, a tidal bore called the pororoca roars upriver at speeds of more than 24 kilometres (15 miles) per hour forming a four-metre (12-foot) water wall.
- Marajo Island
- Tocantins River
- Para River
Amazon River Animals
Freshwater dolphin - These pink dolphins detect prey in the muddy river waters with echo-location. Necks twistable at right angles help them slither between flooded trees. Males sometimes twirl sticks to impress females.
Red-bellied piranha – Piranha fish have sharp, tightly packed teeth for tearing meat. They pinpoint struggling or bleeding animals in the water by smell and with an organ that detects changes in water pressure.
Scarlet macaw – Among the world’s largest parrots, they can measure almost one metre (three feet) from beak to tail and weigh more than a kilogram (2.2 pounds). Highly intelligent, some have lived for 75 years.
Manatee – A relation of elephants, these aquatic mammals can weigh a massive 600 kilograms (1,300 pounds), reach four metres (13 feet) long, and eat 15 per cent of their body weight in vegetation on a daily basis.
Boa constrictor - These snakes kill by crushing creatures in their coils before swallowing them. Up to a staggering four metres (14 feet) long, they can eat prey whole by dislocating their jaws.
Jaguar – Earth’s third-biggest cat after tigers and lions, jaguars can be 1.8 metres (six feet) long and weigh 550 kilograms (250 pounds). Once widespread, they’re now common only in remote regions like the Amazon.
Urania moth – These vivid, iridescent moths are active during the day-unlike the vast majority of moths – and live along rainforest riverbanks. They are migratory, often flying along the course of rivers.
Toucan - The toucan’s bright-coloured bill can reach a huge 10 centimetres (7.5 inches) long -that’s 30 per cent of the bird’s body length! The beak is very light though because it’s honeycombed with air.
Facts about Amazon river
Bridging the Amazon - No bridge crosses the river for over 4,000km (2,500mi). The lack of towns makes it hard to justify the project.
Something fishy – A whopping 15 per cent of the world’s fish species – that’s 3,000 freshwater fish – live in the Amazon.
Jungle city - Manaus, a port city home to 1.6 million, is among Earth’s remotest cities. It’s accessible only by river or one paved highway.
Floods, ahoy - The Amazon’s water level can fluctuate by a staggering 15m (50ft) each year-enough to submerge 3.5 double-decker buses.
The way is blocked - The Amazon emptied into the Pacific until 15 million years ago. The rising Andes range blocked its route so it had to divert.