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

How Canada’s growing presence in Latin America is hurting the environment (Sep 22 2023)
- Canada is up for a periodic U.N. review of its environmental and human rights record in Latin America, and activist groups want to make sure the country is held accountable for lacking regulations and oversight.
- The country is a leader in mining and oil investment in the region but doesn’t do enough to protect against deforestation, pollution and human rights violations against local communities, according to a series of reports published by activist organizations.
- The organizations said Canada should implement new regulations to protect environmental defenders and sign onto ILO Convention 169.

EU bill and new green policies spur progress on Brazil’s cattle tracking (Sep 21 2023)
- Brazilian banks have created new rules for releasing credit to meatpackers and slaughterhouses in Amazonian states in which their clients must implement traceability and monitoring systems by 2025 to show that their cattle didn’t come from illegal deforestation.
- Even the powerful Brazilian Agriculture and Livestock Confederation (CNA) recognizes the cattle tracking demand and proposes a traceability model to the federal government.
- A new study shows that existing cattle companies’ zero-deforestation commitments have reduced Brazilian Amazon deforestation by 15% and that the devastation could be halved by scaling up the implementation of supply chain policies.
- The ideal animal tracking model is individual, but experts defend a middle-of-the-road solution to reduce illegal deforestation based on cross-referencing from inter-ranch cattle transport data and the Rural Environmental Registry (CAR).

Amazonian Indigenous leaders call for 80×2025 at Climate Week (commentary) (Sep 19 2023)
- As the world gathers in New York for Climate Week, Indigenous leaders are calling on UN delegates, environmental organizations, and the research community to back a stronger goal for Amazon protection.
- A central element of the “Amazonia For Life” campaign endorsed by 511 Indigenous nations across Amazonia and 1,200 organizations around the world, it calls on governments to protect at least 80% of the Amazon by 2025.
- “As a mother, a grandmother and a voice for a coalition of Indigenous peoples…I urge every state and each one of you to join us in our fight to protect at least 80% of Amazonia by 2025,” a new op-ed states.
- This post is a commentary. The views expressed are those of the author, not necessarily Mongabay.

‘We don’t have much time’: Q&A with climate scientist Pierre Friedlingstein (Sep 13 2023)
- “It’s not going in the right direction yet,” Pierre Friedlingstein tells Mongabay of the effort to meet the Paris Agreement goals; a member of the IPCC and a climate professor, he says he’s mildly optimistic about the trend in global emissions.
- Friedlingstein says he’s hoping deforestation will go down in the coming years in Brazil, but he’s not sure that Indonesia, another major global carbon sink, is ready to go in the right direction at the moment.
- He says the COVID-19 pandemic showed that climate is still “not on the top of the list” of government priorities, given that all nations sought to boost economic growth after lockdowns, despite the carbon emissions they incurred.

Peru signs $20-million debt-for-nature swap with focus on Amazon rainforest (Sep 12 2023)
- Peru struck a $20 million debt-for-nature swap agreement with the U.S. that transfers debt payments to conservation initiatives like improving protected areas and natural resource management.
- The deal also included four NGOs: Conservation International, The Nature Conservancy, Wildlife Conservation Society and World Wildlife Fund. The groups donated a combined $3 million in addition to the $15 million contributed by the U.S.
- This is the third debt-for-nature swap deal struck with Peru. The U.S. has now made 13 debt-for-nature and debt-for-climate swaps in Latin America and 22 worldwide.

Deforestation in the Amazon rainforest continues to plunge (Sep 8 2023)
- Deforestation in the Brazilian Amazon continues to decline, according to data released today by Brazil’s national space research institute, INPE.
- INPE’s deforestation alert system indicates that forest clearing in Brazil’s portion of the Amazon in August declined 66% compared to the same month last year.
- Deforestation in the Brazilian Amazon has seen a decrease for five consecutive months. This follows President Luiz Inácio Lula da Silva’s commitment to curb the escalating forest loss in the region.
- Brazil is set to release its annual assessment of deforestation for the year ending July 31 in the coming weeks.

El Niño hurts carbon storage in South America’s tropical forests, study says (Sep 8 2023)
- Climate change and El Niño are the main forces behind spiking temperatures across South America, raising questions about countries’ preparedness for extreme climate events as well as about the damage being done to the environment.
- A new study published this month in Nature revealed that, during extremely hot and dry conditions, tropical forests in South America stop acting as carbon sinks.
- But the study also found that tropical forests aren’t becoming more sensitive to drought, so conserving them can still be used to fight climate change.

How the Amazon’s ‘greatest devastator’ sold cattle to a Carrefour supplier  (Aug 29 2023)
- Arrested by Brazilian Federal Police, cattle rancher Bruno Heller and relatives have already received over $5 million in environmental fines. He is also suspected of land grabbing. 
- Heller transported cattle from a family farm fined for environmental violations to two other properties free from environmental implications — this maneuver is an indication of the so-called “cattle laundering.”
- A Frialto Group meatpacking plant confirmed that it slaughtered 249 animals for the Heller family. The facility supplies Carrefour, but the French retail company states that the meat from animals raised by Heller did not reach its supermarkets.

Brazilian Indigenous artists take the forest to the world (Aug 29 2023)
- In recent years, several exhibitions held abroad have featured Indigenous people from Brazil and Latin America, giving unprecedented visibility to artists historically erased by gallery owners and museums.
- Some examples include Siamo Foresta in Milan; The Yanomami Struggle in New York, and BEĨ: Benches of Brazilian Indigenous Peoples in Japan.
- According to curators, the works transcend a mere aesthetic vision, being deeply connected to each people’s cosmologies, in addition to taking political and socioenvironmental issues into museums and galleries.

A tale of two biomes as deforestation surges in Cerrado but wanes in Amazon (Aug 23 2023)
- Brazil has managed to bring down spiraling rates of deforestation in the Amazon Rainforest in the first half of this year, but the neighboring Cerrado savanna has seen a wave of environmental destruction during the same period.
- The country’s second largest biome, the Cerrado is seeing its highest deforestation figure since 2018; satellite data show 3,281 hectares (8,107 acres) per day have been cleared since the start of the year through Aug. 4.
- The leading causes of the rising deforestation rates in the Cerrado are a disparity in conservation efforts across Brazil’s biomes, an unsustainable economic model that prioritizes monocultures, and escalating levels of illegal native vegetation clearing.
- Given the importance of the Cerrado to replenish watersheds across the continent, its destruction would affect not just Brazil but South America too, experts warn, adding that the region’s water, food and energy security are at stake.

PICTURES OF THE AMAZON RAINFOREST