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

Deforestation falls for 8th straight month in the Amazon rainforest, but rises in the cerrado (Dec 8 2023)
- Deforestation in the Brazilian Amazon has decreased for the eighth consecutive month, but damage is rising in the cerrado, a tropical woody grassland that’s adjacent to Earth’s largest rainforest.
- According to data released today by Brazil’s National Space Research Institute (INPE), forest clearing in November totaled 201 square kilometers, brining the cumulative loss for the past twelve months to 5,206 square kilometers – 51% less than last year.
- The decline in deforestation has persisted despite one of the most severe droughts ever recorded in the Amazon.
- However, while deforestation in the Amazon rainforest has decreased, it has reached the highest level in at least five years in the cerrado.

Brazil cattle traceability program to limit deforestation in Pará state (Dec 4 2023)
- A new traceability program will keep tabs on the millions of cattle present throughout the state of Pará, in northern Brazil, where the Amazon Rainforest has been hit especially hard by deforestation from cattle ranching.
- The tagging program aims to monitor all transported cattle transported through the state by December 2025 and the permanent herd of approximately 24 million cattle by December 2026.
- The program was created last week through a decree signed by Pará governor Helder Barbalho following the introduction of the Leaders Declaration on Food Systems, Agriculture and Climate Action at COP28, the annual UN climate conference.

What Brazil should have said at COP28 but didn’t (commentary) (Dec 4 2023)
- Brazil’s President Lula made important contributions to COP28 in demanding that the 1.5°C temperature increase limit be respected, in recognizing the risk of Amazon forest collapse, and in promising to end Brazil’s Amazon deforestation by 2030.
- Lula failed to explain how zero deforestation would be achieved, implicitly relying only on the Ministry of Environment’s command and control operations against illegal clearing. The causes of deforestation must be addressed, many of which are being strengthened by the rest of Lula’s presidential administration.
- These include legalization of illegal land claims in government land and highway projects such as BR-319 and associated side roads that would open vast areas of Amazon forest to the entry of deforesters. Brazil’s plans for opening new oil and gas extraction areas and expanding existing ones contradict the discourse on limiting temperature rise to 1.5°C.
- This post is a commentary. The views expressed are those of the author, not necessarily of Mongabay.

Brazil proposes $250 billion “Tropical Forests Forever” fund for rainforests (Dec 3 2023)
- Brazil has proposed a new $250 billion mechanism for conserving the world’s tropical rainforests.
- The “Tropical Forests Forever” fund, sourced from governments and the private sector, would disburse money to tropical countries that achieve set thresholds for limiting deforestation.
- The proposal, conceptually similar to past initiatives, emerges amid a growing interest in nature-based solutions for addressing climate change and other environmental challenges.
- It comes as Brazilian President Luiz Inácio Lula da Silva is repositioning the country as a leader in efforts to address climate change.

Cargill widens its deforestation-free goals, but critics say it’s not enough (Nov 29 2023)
- Cargill has announced its Brazil, Uruguay and Argentina supply chains will be free of deforestation and land conversion by 2025.
- The commitments also expand to all row crops in those countries, including soy, corn, wheat and cotton.
- While conservation groups have welcomed the expanded commitment, they say it still leaves out countries like Bolivia, Paraguay and Colombia, where deforestation from the expanding agricultural frontier continues to increase.

Paradise lost? Brazil’s biggest bauxite mining firm denies riverine rights (Nov 27 2023)
- Mineração Rio do Norte (MRN), Brazil’s largest bauxite producer, launched a new mining project in the Amazon region in 2019 but failed to notify and consult four impacted traditional riverine communities that have been established for generations. The villages say their lives are heavily impacted.
- MRN’s stance of no significant impact is backed by IBAMA, Brazil’s environmental agency, because it only is required to recognize Indigenous and Quilombola populations as legitimate traditional peoples guaranteed prior, free, informed consultation — a right enshrined in international law.
- Other traditional riverine communities are being denied such a right, say critics who are calling on President Luiz Inácio Lula da Silva’s government to instruct IBAMA to reduce the impact of mining on riverine communities.
- Action by IBAMA could help preserve the way of life for hundreds of traditional riverine people likely to be affected by a series of new mines planned by MRN. The ruling could also act as a precedent for other traditional communities not currently guaranteed prior, free, informed consultation.

Jane Goodall and Dax Dasilva partner with Amazon Indigenous youth for new Roots & Shoots program (Nov 24 2023)
- Jane Goodall is partnering with Dax Dasilva to bring her Roots & Shoots youth program to the Brazilian Amazon to help equip Indigenous youth to protect their ancestral lands.
- On Goodall’s first in-depth visit to the Amazon, she and Dasilva met with Juma Xipaya, who leads resistance against dams and illegal mining and logging in her indigenous territory of the Xipaya, located in Brazil’s Pará state.
- Deforestation and climate change are drying and degrading the Amazon rainforest, and this year saw historic droughts across the region.
- Indigenous territories remain important strongholds for safeguarding the remaining Amazon Rainforest.

Mongabay CEO discusses slowdown in Amazon loss and other positive news (Nov 21 2023)
- It’s been an eventful couple of months for the Amazon Rainforest and for the Mongabay newsroom.
- Brazil’s National Institute for Space Research (INPE) recently shared data showing a 22% decline in deforestation for the year ending July 31, 2023.
- In other exciting news, Mongabay was awarded the prestigious 2023 Biophilia Award for Environmental Communication recently. Past winners have included Pulitzer-winning journalist Elizabeth Kolbert and The Guardian.
- Mongabay has also just launched an entirely new bilingual bureau in Africa. Here to discuss all these developments on this episode of the Mongabay Newscast is CEO and editor-in-chief Rhett Butler.

Jurisdictional REDD+ ready to fund forest-positive, socially-inclusive development in the Amazon and beyond (commentary) (Nov 20 2023)
- Jurisdictional REDD+ (JREDD) is designed to fund regional transitions to forest-positive, socially-inclusive rural development. It is fundamentally different than private forest carbon projects, which have come under scrutiny for overstating their climate benefits.
- JREDD rewards forest carbon emissions reductions already achieved across entire jurisdictions–states and nations–and provides a platform for the full participation of Indigenous peoples, local communities and farmers; it features a leadership role for governments that are becoming more transparent and inclusive in the process.
- The steep decline in deforestation in the Brazilian Amazon means that several states are poised to issue a large volume of high-integrity, verified JREDD credits from 2024 onward. If the demand for these credits is sufficient, sales revenues could help states tame extensive forest frontiers with transparency and accountability, inspiring other regions to do the same.
- This post is a commentary. The views expressed are those of the author, not necessarily Mongabay.

End of impunity for Indigenous killings in sight for Brazil’s Guajajara (Nov 20 2023)
- Indigenous forest guardian Paulo Paulino Guajajara was killed in November 2019 in an alleged ambush by illegal loggers in the Arariboia Indigenous Territory in Brazil’s Maranhão state.
- Mongabay’s Karla Mendes, who interviewed Paulo for a documentary film nine months before his death, returned to Arariboia in August 2023 to talk with his family and the other guardian who survived the attack, Laércio Guajajara, and shine a light on a case that still hasn’t gone to trial after four years.
- “If those invaders had managed to kill us both, me and Paulo, they were going to hide us in the forest. Who would find us? Nobody was ever going to find me or Paulo again in a forest of that size,” Laércio says of his will to warn the guardians about Paulo’s murder, even as he suffered four gunshot wounds.
- Justice may soon be on the horizon for the Guajajara people: Paulo’s case will be the first killing of an Indigenous defender that will go before a federal jury, likely in the first half of 2024, after a court in late October denied a motion by those accused to try the case in state court.

PICTURES OF THE AMAZON RAINFOREST