The Amazon Rainforest: The World's Largest Rainforest

By Rhett A. Butler [Last update June 4, 2020]

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

Book: A perfect storm in the Amazon (May 23 2023)
- Mongabay has begun publishing a new edition of the book, “A Perfect Storm in the Amazon,” in short installments and in three languages: Spanish, English and Portuguese.
- Author Timothy J. Killeen is an academic and expert who, since the 1980s, has studied the rainforests of Brazil and Bolivia, where he lived for more than 35 years.
- Chronicling the efforts of nine Amazonian countries to curb deforestation, this edition provides an overview of the topics most relevant to the conservation of the region’s biodiversity, ecosystem services and Indigenous cultures, as well as a description of the conventional and sustainable development models that are vying for space within the regional economy.
- Click the “Perfect Storm in the Amazon” link atop this page to see chapters 1-13 as they are published during 2023.

Critics question causes behind major oil spill in Ecuadorian Amazon (May 22 2023)
- An oil pipeline operated by the state-owned Petroecuador ruptured earlier this month in the province of Sucumbíos, causing concern about contamination of rivers that extend to other parts of the rainforest.
- Petroecuador said the spill occurred after an attack on the pipeline. But environmental activists question those claims.
- Some communities reported seeing contamination downriver and expressed concern that the spill would have a long-term impact on the local ecosystem.

Study shows 10 million acres of Colombian rainforest at risk without new policies (May 22 2023)
- Researchers from the Amazonian Scientific Research Institute Sinchi analyzed the potential future of the Colombian Amazon Rainforest up until 2040; the results, based on analyzing 18 years of data from forest monitoring, show three possible future scenarios depending on deforestation policies.
- With current trends, loss could amount to 2.1 million hectares (5.2 million acres) of Amazon Rainforest. However, in the worst-case scenario — if extractivist policies are implemented — deforestation could reach 4.3 million hectares (10.6 million acres).
- On the other hand, if the cattle ranching industry is reduced and sustainable development achieved, at least 3.5 million hectares (8.6 million acres) of forest could be saved by 2040.

Second chance for Lula as controversial Amazon dam goes up for renewal (May 18 2023)
- In the biological and cultural hotspot of the Volta Grande in Brazil’s Amazon, Indigenous communities and scientists have teamed up to monitor the impacts of the Belo Monte hydroelectric project, one of the biggest in the world.
- The dam complex has diverted 80% of the Xingu River’s water flow, significantly affecting the aquatic life in the Volta Grande river bend and pushing the entire ecosystem toward collapse, along with the local communities who rely on it.
- The complex’s environmental license, which lasts six years and dictates the amount of water flowing through Belo Monte, is currently up for review by the federal environmental protection agency, IBAMA.
- President Luiz Inácio Lula da Silva played a key role in pushing for the construction of Belo Monte, and now, back in power, can influence a new path for the environment and local communities, activists say.

Indigenous chief shot in head in Brazil’s ‘palm oil war’ region; crisis group launched (May 16 2023)
- On May 14, Indigenous chief Lúcio Tembé was shot by gunmen on an unpaved road in Brazil’s northern Pará state. This is the latest episode of violence in an area facing an outbreak of land conflicts between a major palm oil company and local communities, the so-called “palm oil war.”
- The Federal Public Ministry raised the possibility of the crime’s connection to conflicts with palm oil companies in the region and requested urgent measures of the Federal Police and Pará’s State Department of Public Security and Social Defense (Segup) in view of the intense level of conflict in the region “with concrete risks to the Indigenous peoples’ life and physical integrity.”
- A crisis committee to contain escalating conflicts in the region was announced on May 16; the crime is being investigated by the Federal Police and the Quatro Bocas municipal police station, urging that any relevant information be forwarded via the hotline 181 under guaranteed confidentiality.
- Some readers may find the images below disturbing, discretion is advised.

Targeting 3% of protected areas could accelerate progress on 30×30 goals, says Global Conservation’s Jeff Morgan (May 16 2023)
- In December, world leaders adopted the Kunming-Montreal Global Biodiversity Framework, targeting the conservation of 30% of Earth by 2030.
- However, Jeff Morgan, founder of Global Conservation, points out that simply designating protected areas is not enough to safeguard nature. His organization, therefore, focuses on strengthening protection within UNESCO World Heritage Sites in lower and middle-income countries, utilizing cost-effective technologies for law enforcement against poaching, illegal logging, and more.
- Global Conservation currently operates across 22 national parks and 10 marine parks in 14 countries and aims to expand its work to 100 sites by 2033. Morgan believes that this focus on existing national parks and habitats is the most efficient and cost-effective way to achieve climate goals.
- Morgan recently spoke with Mongabay founder Rhett A. Butler about Global Conservation’s approach.

Amazon Rainforest loss could reach new height in just 5 years, study says (May 11 2023)
- A recent study has found that in the five-year period between 2021 and 2025, the Amazon could lose half the total forest cover it lost in the previous 20 years, amounting to a further loss of 237,058 square kilometers (91,529 square miles).
- From 2001-20, the rainforest lost more than 500,000 km2 (200,000 mi2) of forest cover, an area larger than Spain, mostly because of road development, agricultural expansion and mining.
- Deforestation rates continue to accelerate in almost all nine Amazonian countries, especially in Brazil, Bolivia, Peru and Colombia.
- Implementing efficient public policies and strengthening control and monitoring are essential to reduce rising deforestation rates, but experts warn economic interests often clash with conservation efforts in the Amazon.

World’s ‘largest’ tropical reforestation project slowed by Covid, Bolsonaro, fires (May 4 2023)
- In 2017, Conservation International launched what was dubbed the “largest tropical forest restoration in the world” and slated for the Brazilian Amazon. Despite a goal of completing the project by the end of this year, CI is less than 20% of the way there.
- According to project managers, the initiative has been slowed by two main factors: the COVID-19 pandemic and the 2019-2022 presidency of Jair Bolsonaro.
- But fire, once a rarity in the Amazon, has also played a role, destroying 2,700 hectares (nearly 6,700 acres) of restoration areas in 2021 alone.
- Still, the initiative is moving ahead across the “arc of deforestation,” with organizers hoping to prove it’s possible to restore the rapidly receding southern edge of the Brazilian Amazon before a large part of the rainforest biome hits a tipping point and changes over to savanna — releasing huge amounts of carbon to the atmosphere.

In a Bolivian protected area torn up for gold, focus is on limiting damage (May 2 2023)
- Artisanal gold mining by local cooperatives abounds in protected areas across Bolivia, in particular the Apolobamba highlands near the border with Peru.
- The mining boom here began in the late 1990s, and since then the cooperatives have continued to use mercury amalgamate the gold.
- There are worries over mercury contamination as well as the diversion of river flows away from wetlands to the mines.
- NGOs working with the cooperatives say the local miners are keen on making their operations more sustainable, but that the cost and lack of government support are hurdles to achieving this.

Mouth of the Amazon oil exploration clashes with Lula’s climate promises (Apr 28 2023)
- State-owned Petrobras has requested a license to investigate an oil site in a region in the north of Brazil where the Amazon River meets the Atlantic Ocean.
- The region is home to swathes of mangroves and coral reefs that environmentalists say are highly biodiverse and fundamental to local communities.
- Experts demand that Brazil’s environmental agency reject the license, saying the government hasn’t conducted the required detailed studies to assess the potential impact.
- Critics warn that pursuing fossil fuels contradicts President Luiz Inácio Lula da Silva’s vows to adopt a renewable energy strategy and clashes with global climate change guidelines.

PICTURES OF THE AMAZON RAINFOREST