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

Can a new regional pact protect the Amazon from environmental crime? (commentary) (Mar 28 2023)
- Police, prosecutors, money-laundering experts and others convened last week in Brazil to tackle drug and environmental crimes like illegal mining and logging that are growing in scale across the Amazon.
- The group resolved to move law enforcement beyond occasional raids and periodic destruction of machinery used by organized crime syndicates and toward a concerted and pan-Amazonian push for local, regional and global cooperation on law enforcement.
- While acknowledging the increasing scale of these crimes, participants were optimistic: “We are living in a new moment to fight environmental crime and protect the Amazon,” said the newly appointed director for Amazon environmental crime with Brazil’s federal police, for example.
- This post is a commentary. The views expressed are those of the authors, not necessarily of Mongabay.

Tropical forest regeneration offsets 26% of carbon emissions from deforestation (Mar 23 2023)
- A new study published in the journal Nature analyzed satellite images from three major regions of tropical forest on Earth — Amazon, Central Africa and Borneo — and showed recovering forests offset just 26% of carbon emissions from new tropical deforestation and forest degradation in the past three decades.
- Secondary forests have a good potential to absorb carbon dioxide from the atmosphere and could be an ally in addressing the climate crisis, but emissions generated from deforestation and forests lost or damaged due to human activity currently far outpace regrowth.
- The study provides information to guide debates and decisions around the recovery of secondary forests and degraded areas of the Brazilian Amazon — around 17% of the ecosystem is in various stages of degradation and another 17% is already deforested.
- Since Brazil’s new President Luiz Inácio Lula da Silva took office, projects to curb deforestation are in place, but plans to protect recovering areas remain unclear.

Make it local: Deforestation link to less Amazon rainfall tips activism shift (Mar 14 2023)
- A new study supports mounting evidence that deforestation in the Amazon Rainforest correlates with a reduction in regional rainfall.
- Experts say this research reinforces the findings of other studies that claim the Amazon is leaning toward its “tipping point” and the southern regions are gradually becoming drier.
- Environmentalists see this research as an opportunity to reshape conservation activism and policy towards local communities.

Mobilizing Amazon societies to reduce forest carbon emissions and unlock the carbon market (commentary) (Mar 13 2023)
- Brazil could generate $10 billion or more from the global voluntary carbon market over the next four years through the sale of credits from Amazon states’ jurisdictional REDD+ programs; some states are already finalizing long-term purchase agreements.
- This funding would flow to those who are protecting the forest – Indigenous peoples and traditional communities, farmers, businesses, and government agencies – and the prospect of this funding could mobilize collective action to reduce emissions from illegal deforestation and degradation.
- Rapid progress in reducing emissions from Amazon deforestation and forest degradation – which represent half of Brazil’s nation-wide emissions – would also position Brazil to capture significant international funding for its national decarbonization process through the regulated carbon market that is under development through the UN Paris Agreement.
- This post is a commentary. The views expressed are those of the authors, not necessarily of Mongabay.

Most of ‘top ten’ hotspots for jaguar conservation are in Brazil’s Indigenous territories (Mar 10 2023)
- Jaguars are essential to healthy ecosystems but have been eradicated from almost 50% of their historical range, and by some estimates, only 64,000 individuals remain.
- Brazil is home to half of the world’s jaguars, and a group of researchers has identified the highest-priority protected areas in the Brazilian Amazon for jaguar conservation.
- The top 10 highest-priority protected areas fall primarily across the arc of deforestation in southern and western Brazil, and eight of these are Indigenous territories.
- Researchers say conservation efforts must include strengthened participation of Indigenous peoples and local communities, increased funding and support for protected areas and environmental agencies, and the implementation of more robust environmental policies.

Struggles loom as Bolivia prepares new plan to clean up its mercury problem (Mar 9 2023)
- Bolivia’s failure to combat illegal gold mining led to international outcry last year, as deforestation and mercury pollution continued to run rampant.
- Earlier this month, the government announced two plans to formalize small-scale and illegal gold mining operations and introduce technology that could help replace mercury.
- However, some critics say the government has a bad track record for implementing sweeping industry regulations, which might look good on paper but fall flat in practice.
- Major road investments in mining areas could also increase illegal activity at the same time the government is implementing regulations, as it will be easier for heavy machinery to access rural areas.

Amazon deforestation linked to reduced Tibetan snows, Antarctic ice loss: Study (Mar 8 2023)
- Earth’s climate is controlled by a complex network of interactions between the atmosphere, oceans, lands, ice and biosphere. Many elements in this system are now being pushed toward tipping points, beyond which changes become self-sustaining, with the whole Earth system potentially shifting to a new steady state.
- A recent study analyzed 40 years of air temperature measurements at more than 65,000 locations to investigate how changes in one region rippled through the climate system to affect temperatures in other parts of the globe. Computer models then simulated how these links may be affected by future climate change.
- Researchers identified a strong correlation between high temperatures in the Amazon Rainforest and on the Tibetan Plateau. They found a similar relationship between temperatures in the Amazon and the West Antarctic Ice Sheet.
- Deforestation in the Amazon likely influences the Tibetan Plateau via a convoluted 20,000-kilometer (12,400-mile) pathway driven by atmospheric and oceanic circulation patterns. The study suggests that a healthy, functioning Amazon is crucial not only for the regional climate in Brazil, but for the whole Earth system.

In Brazil, criminals dismantle one of the best-preserved swaths of the Amazon (Feb 23 2023)
- The Terra do Meio Ecological Station spans 3.37 million hectares (8.33 million acres) in the Brazilian Amazonian state of Pará and is home to hundreds of wildlife species, including many threatened with extinction.
- Despite its protected status, Terra do Meio has come under growing pressure, with data showing deforestation doubling in 2022, reaching 4,300 hectares (nearly 11,000 acres).
- Environmentalists say the destruction within Terra do Meio is being driven by illegal loggers, miners and land speculators — and they fear a new road slicing through the reserve could usher in more destruction.
- Advocates are placing their hopes in Brazil’s new president, Luiz Inácio Lula da Silva, who has promised to crack down on invasions into protected reserves and rein in sky-high deforestation rates.

France seeks EU okay to fund biomass plants, burn Amazon forest to power Spaceport (Feb 23 2023)
- As the European Union finalizes its third Renewable Energy Directive (REDIII), France is seeking an exemption to enable the European Space Agency and French Space Agency to build and operate two biomass power plants in French Guiana. An estimated 5,300 hectares of Amazon rainforest would need to be cut and biomass crops grown on the cleared land to service the power plants.
- The biomass would be burned to help power Europe’s Spaceport in French Guiana. The exemption request — which would allow EU and French public subsidies to flow to a France-based bioenergy plant builder — comes as the EU moves toward banning commodities contributing significantly to global deforestation.
- This latest move by France comes soon after it won an appeal of a 2021 court ruling in French Guiana that blocked massive Amazon clearcutting for croplands to provide liquid biofuels for three new, large power plants to make energy for the Fr. Guiana populace. Decisions on the REDIII exemption and liquid biofuels plan could come in March.
- Environmentalists are decrying the French Guiana biomass plans — and French President Emmanuel Macron’s passive support of them — not only for the Amazon deforestation it will cause, but because biomass burned to produce energy has been scientifically shown to release higher levels of carbon emissions than coal.

Carbon uptake in tropical forests withers in drier future: Study (Feb 23 2023)
- A new study incorporating satellite data on organic material, or biomass, in tropical forests with experimental data about the effects of temperature and precipitation suggests that forests may lose substantial amounts of carbon by the end of the 21st century.
- Even with low continued carbon emissions, tropical forests, especially those in the southern Amazon, could lose between 6.8 and 12% of their aboveground carbon. With higher emissions, they could lose 13.3 to 20.1% of their carbon stores.
- The results highlight the need to reduce global temperatures rapidly to maintain the healthy forests best able to sequester carbon from the atmosphere.
- The team reported their findings Feb. 6 in the journal Nature Climate Change.

PICTURES OF THE AMAZON RAINFOREST