The Amazon Rainforest: The World's Largest Rainforest

By Rhett A. Butler [Last update Apr 4, 2024]

The Amazon River Basin is home to the largest rainforest on Earth. The basin -- roughly the size of the forty-eight contiguous United States -- covers some 40 percent of the South American continent and includes parts of eight South American countries: Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, Guyana, and Suriname, as well as French Guiana, a department of France.

Reflecting environmental conditions as well as past human influence, the Amazon is made up of a mosaic of ecosystems and vegetation types including rainforests, seasonal forests, deciduous forests, flooded forests, and savannas.

The basin is drained by the Amazon River, the world's largest river in terms of discharge, and the second longest river in the world after the Nile. The river is made up of over 1,100 tributaries, 17 of which are longer than 1000 miles, and two of which (the Negro and the Madeira) are larger, in terms of volume, than the Congo river.

The river system is the lifeline of the forest and its history plays an important part in the development of its rainforests.

WHERE THE AMAZON RANKS AMONG GLOBAL RAINFORESTS

The Amazon is the world's biggest rainforest, larger than the next two largest rainforests — in the Congo Basin and Indonesia — combined.

As of 2020, the Amazon has 526 million hectares of primary forest, which accounts for nearly 84% of the region's 629 million hectares of total tree cover. By comparison, the Congo Basin has around 168 million hectares of primary forest and 288 million hectares of tree cover, while the combined tropical areas of Indonesia, Papua New Guinea, Malaysia, and Australia have 120 million hectares of primary forest and 216 million hectares of tree cover.

THE HISTORY OF THE AMAZON RAINFOREST

At one time Amazon River flowed westward, perhaps as part of a proto-Congo river system from the interior of present day Africa when the continents were joined as part of Gondwana. Fifteen million years ago, the Andes were formed by the collision of the South American plate with the Nazca plate. The rise of the Andes and the linkage of the Brazilian and Guyana bedrock shields, blocked the river and caused the Amazon to become a vast inland sea. Gradually this inland sea became a massive swampy, freshwater lake and the marine inhabitants adapted to life in freshwater. For example, over 20 species of stingray, most closely related to those found in the Pacific Ocean, can be found today in the freshwaters of the Amazon.

About ten million years ago, waters worked through the sandstone to the west and the Amazon began to flow eastward. At this time the Amazon rainforest was born. During the Ice Age, sea levels dropped and the great Amazon lake rapidly drained and became a river. Three million years later, the ocean level receded enough to expose the Central American isthmus and allow mass migration of mammal species between the Americas.

The Ice Ages caused tropical rainforest around the world to retreat. Although debated, it is believed that much of the Amazon reverted to savanna and montane forest (see Ice Ages and Glaciation). Savanna divided patches of rainforest into "islands" and separated existing species for periods long enough to allow genetic differentiation (a similar rainforest retreat took place in Africa. Delta core samples suggest that even the mighty Congo watershed was void of rainforest at this time). When the ice ages ended, the forest was again joined and the species that were once one had diverged significantly enough to be constitute designation as separate species, adding to the tremendous diversity of the region. About 6000 years ago, sea levels rose about 130 meters, once again causing the river to be inundated like a long, giant freshwater lake.

Note: Human populations have shaped the biodiversity of the Amazon. See Amazon people for more.

THE AMAZON RIVER TODAY

Today the Amazon River is the most voluminous river on Earth, carrying more than five times the volume of the Congo or twelve times that of the Mississippi, draining an area nearly the size of the forty-eight contiguous United States. During the high water season, the river's mouth may be 300 miles wide and every day up to 18 billion cubic meters (635 billion cubic feet) of water flow into the Atlantic. That discharge, equivalent to 209,000 cubic meters of water per second (7.3 million cubic feet/sec), could fill over 7.2 million Olympic swimming pools per day or supply New York City's freshwater needs for nine years.

The force of the current -- from sheer water volume alone -- causes Amazon River water to continue flowing 125 miles out to sea before mixing with Atlantic salt water. Early sailors could drink freshwater out of the ocean before sighting the South American continent.

The river current carries tons of suspended sediment all the way from the Andes and gives the river a characteristic muddy whitewater appearance. It is calculated that 106 million cubic feet of suspended sediment are swept into the ocean each day. The result from the silt deposited at the mouth of the Amazon is Majaro island, a river island about the size of Switzerland.

The Amazon's influence on the movement of moisture extends beyond the water that flows down the Amazon river. The trees of the Amazon rainforest pump vast quantities of water vapor into the atmosphere every day via transpiration. While much of this water falls locally as rain, some of this moisture is carried by airflows across other parts of the continent, including the agricultural heartland of South America to the south. This movement has been likened to "flying rivers". By one estimate, 70% of Brazil's gross national product comes from areas that receive rainfall generated by the Amazon rainforest.

THE AMAZON RAINFOREST

While the Amazon Basin is home to the world's largest tropical rainforest, the region consists of myriad other ecosystems ranging from natural savanna to swamps. Even the rainforest itself is highly variable, tree diversity and structure varying depending on soil type, history, drainage, elevation, and other factors. This is discussed at greater length in the Amazon rainforest ecology section.

AMAZON BIODIVERSITY

The Amazon is home to more species of plants and animals than any other terrestrial ecosystem on the planet -- perhaps 30 percent of the world's species are found there. The following numbers represent a sampling of its astounding levels of biodiversity:

• 40,000 plant species
• 16,000 tree species
• 3,000 fish species
• 1,300 birds
• 430+ mammals
• 1,000+ amphibians
• 400+ reptiles

THE CHANGING AMAZON RAINFOREST

The Amazon has a long history of human settlement, but in recent decades the pace of change has accelerated due to an increase in human population, the introduction of mechanized agriculture, and integration of the Amazon region into the global economy. Vast quantities of commodities produced in the Amazon — cattle beef and leather, timber, soy, oil and gas, and minerals, to name a few — are exported today to China, Europe, the U.S., Russia, and other countries. This shift has had substantial impacts on the Amazon.

This transition from a remote backwater to a cog in the global economy has resulted in large-scale deforestation and forest degradation in the Amazon — more than 1.4 million hectares of forest have been cleared since the 1970s. An even larger area has been affected by selective logging and forest fires.

Conversion for cattle grazing is the biggest single direct driver of deforestation. In Brazil, more than 60 percent of cleared land ends up as pasture, most of which has low productivity, supporting less than one head per hectare. Across much of the Amazon, the primary objective for cattle ranching is to establish land claims, rather than produce beef or leather. But market-oriented cattle production has nonetheless expanded rapidly during the past decade.

Industrial agricultural production, especially soy farms, has also been an important driver of deforestation since the early 1990s. However since 2006 the Brazil soy industry has had a moratorium on new forest clearing for soy. The moratorium was a direct result of a Greenpeace campaign.

Mining, subsistence agriculture, dams, urban expansion, agricultural fires, and timber plantations also result in significant forest loss in the Amazon. Logging is the primary driver of forest disturbance and studies have shown that logged-over forests — even when selectively harvested — have a much higher likelihood of eventual deforestation. Logging roads grant access to farmers and ranchers to previous inaccessible forest areas.

Deforestation isn't the only reason the Amazon is changing. Global climate change is having major impacts on the Amazon rainforest. Higher temperatures in the tropical Atlantic reduce rainfall across large extents of the Amazon, causing drought and increasing the susceptibility of the rainforest to fire. Computer models suggest that if current rates of warming continue, much of the Amazon could transition from rainforest to savanna, especially in the southern parts of the region. Such a shift could have dramatic economic and ecological impacts, including affecting rainfall that currently feeds regions that generate 70 percent of South America's GDP and triggering enormous carbon emissions from forest die-off. These emissions could further worsen climate change.

PROTECTING THE AMAZON RAINFOREST

While destruction of the Amazon rainforest is ongoing, the overall rate of deforestation rate in the region dropped between the mid-2000s and mid-2010s, mostly due to to the sharp decline in forest clearing in Brazil. However deforestation has been steadily rising in the region in more recent years.

Brazil's decline in its deforestation rate between 2004 and 2012 was attributed to several factors, some of which it controls, some of which it doesn't. Between 2000 and 2010 Brazil established the world's largest network of protected areas, the majority of which are located in the Amazon region. In 2004, the government implemented a deforestation reduction program which included improved law enforcement, satellite monitoring, and the provision of financial incentives for respecting environmental laws. Independent public prosecutors offices played a particularly important role in pursing illegal activities in the Brazilian Amazon. The private sector also got involved, especially after 2006 when major crushers established a moratorium on new deforestation for soy. That soy moratorium was followed by the "Cattle Agreement", which major slaughterhouses and beef processors committed to source cattle only from areas where environmental laws were being respected.

However these conservation initiatives started to break down in the Brazilian Amazon in the mid-2010s. Major cattle producers circumvented the rules through livestock laundering, while financial incentives for conserving forests failed to materialize at the expected scale needed to change landowners' behavior. The Temer and Bolsonaro Administrations dismantled environmental regulations, reduced environmental law enforcement, stripped conservation areas and indigenous territories of protections, and encouraged a wide range of industries (mining, logging, agribusiness) to expand extraction and conversion in the Amazon. In 2019, deforestation in the Brazilian started accelerating rapidly.

THE LATEST AMAZON RAINFOREST NEWS

Plans for bauxite mine in Suriname reignite Indigenous land rights debate (Jan 16 2025)
- A bauxite mine run by Chinese corporation Chinalco could begin operating next year, endangering a 280,000-hectare (about 692,000 acres) area of western Suriname inhabited by Indigenous communities.
- The mine will require refurbishing and expanding infrastructure for a harbor and railroad built in the 1970s, and gives the company “priority right” to use the Corantijn river for dredging.
- Indigenous groups said they weren’t properly consulted about the project and that the government is unfairly labeling their territory as public domain.

Safeguarding the shea nut legacy for Ugandan women (Jan 16 2025)
KAL AWINYA, Uganda – In rural Uganda, 34-year-old Adong Betty from Kal Awinya village shares how shea nuts sustain her family and community. Her own childhood was marked by active participation in collecting and processing shea nuts with her mother, instilling in her a deep respect for this tradition. Shea nuts are a critical part […]

Should mining companies consider no-go zones where isolated Indigenous peoples live? (Commentary) (Jan 16 2025)
- Irresponsible mining for critical minerals, like those used in renewable technologies, can threaten the existence of Indigenous peoples in voluntary isolation, who are amongst the world’s most vulnerable populations.
- Companies like Tesla are considering no-go zones where uncontacted people live. While the idea of establishing these zones is increasingly pragmatic, the author says the most crucial thing for companies to do is conduct rigorous human rights due diligence from the initial stages of mine development right through to closure.
- Danielle Martin from the International Council on Mining and Metals (ICMM) says this approach relies on the meaningful and inclusive engagement and the participation of affected Indigenous peoples. But for Indigenous peoples in voluntary isolation, engagement and participation may not be possible and agreement may not be attainable.
- This article is a commentary. The views expressed are those of the authors, not necessarily Mongabay.

Ogoni women restore mangroves and livelihoods in oil-rich Niger Delta (Jan 16 2025)
- After decades of crude oil spills and the introduction of invasive plant species, thousands of hectares of mangroves in the Niger Delta are destroyed, impacting aquatic species and women’s livelihoods.
- Ogoni women from coastal villages, supported by the Lokiaka Community Development Centre, have been at the forefront of reforestation efforts.
- The women have planted 2.6 million mangrove trees since 2018, drawing attention from a government agency that hired them to share their knowledge and plant mangroves for its oil spill rehabilitation project.
- Around 300 women from Ogoni communities have been trained in mangrove reforestation.

Elephants, gorillas and chimps hold out in Cameroon’s largest protected landscape (Jan 16 2025)
- A new survey finds that populations of forest elephants, lowland gorillas and chimpanzees have remained relatively stable in a large landscape in southeastern Cameroon.
- In some cases, populations actually rose significantly in the region’s protected areas, but declined on the outskirts.
- Officials attribute this “positive” trend to hard work and the implementation of a “permanent presence technique” to deter poaching by engaging more closely with local communities.
- However, they say more effort is still needed to combat poaching for tusks and the trafficking of great apes.

Satellite ‘backpacks’ help keep track of parrot migration in Mexico (Jan 16 2025)
- Scientists and conservationists have deployed lightweight satellite backpacks, containing transmitters, to study and understand the migration patterns of thick-billed parrots.
- Teams from San Diego Zoo Wildlife Alliance in the U.S. and conservation NGO Organización Vida Silvestre in Mexico have gathered more than 70,000 data points over four years.
- The data helped them identify corridors that are critical for the birds’ movements; they also served to justify the designation of protected areas that are important for the birds.
- Thick-billed parrots, known for their raucous calls, are an endangered species endemic to Mexico; illegal logging in recent years has led to the degradation of their habitats.

Vested interests and social tribes in the Pan Amazon (Jan 16 2025)
- Local and regional actors, particularly commercial and landowner elites in mid-sized cities, play an important role in the expansion and improvement of road networks. In Brazil, lobbying by private interests played a big role in the development of Rodovia Transamazônica and BR-319.
- In Brazil, agribusinesses exert political power via the Frente Parlamentar da Agropecuária (FPA), often referred to as the Bancada Ruralista, a multi-party congressional voting bloc.
- One of the most significant accomplishment of the ruralistas was their 2012 campaign to modify Brazil’s the Forest Code. Changes included amnesty for property owners who had illegally deforested land before 2008 and adjusted requirements to reforest portions of landholdings that had exceeded legal deforestation limits.

African Parks closes deal to manage Ethiopia’s Gambella National Park (Jan 16 2025)
- South Africa-based conservation NGO African Parks signed a long-term deal in December 2024 to manage Gambella National Park in Ethiopia.
- The agreement brings the number of protected areas under management by African Parks to 23 in 13 countries.
- Gambella is part of a wider landscape that includes Boma and Badilingo national parks, across the border in South Sudan.
- The Gambella region has been conflict-prone in recent years, with a documented history of human rights violations by the Ethiopian government and other groups.

Mongabay documentary spotlights Indigenous alliance to protect Amazon headwaters (Jan 16 2025)
Mongabay’s new short documentary The Time of Water premiered Dec. 16 at the Barcelona Center for Contemporary Culture, in Spain. Directed by Pablo Albarenga and produced with support from the Pulitzer Center and OpenDemocracy, the 18-minute documentary explores the Amazon Sacred Headwaters Alliance and its fight to protect one of the world’s most vital sources […]

1 lynx dead, 3 quarantined after suspected illegal release in Scotland (Jan 16 2025)
What started out as a reported sighting of a pair of Eurasian lynx in the Scottish Highlands has turned out to be an alleged case of “guerrilla rewilding” or, at the very least, illegal release of four individuals of a species long extinct in the area, media reports say. A pair of Eurasian lynx (Lynx […]

Serious groundwater contamination in several parts of India: Report (Jan 16 2025)
A recent analysis has revealed that India’s groundwater contains pollutants in excess of permissible limits. This contamination is driven by both natural geochemical processes and human activities like agricultural and industrial practices, reports contributor Esha Lohia for Mongabay India. To understand the state of groundwater in India, the Central Ground Water Board (CGWB) assessed more […]

Mining in a forest conservation site clouds Republic of Congo’s carbon credit scheme (Jan 16 2025)
- The Republic of Congo set up a REDD+ program in the Sangha and Likouala regions, aiming to reduce deforestation and store carbon from 2020 through to 2024.
- However, in the Sangha region alone, the country’s mining minister has issued at least 79 semi-industrial gold mining and exploration permits since the project began.
- Scientists reviewing images of these mining activities condemn the “reckless” destruction of biodiversity.
- The government says the program stored more than 1.5 million metric tons of carbon in 2020, for which it expects to be paid more than $8 million from the World Bank.

PICTURES OF THE AMAZON RAINFOREST