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

Hopes and fears for the Amazon: Interview with botanist Hans ter Steege (Nov 19 2024)
- Dutch researcher and tree expert Hans ter Steege is the founder of the Amazon Tree Diversity Network, which brings together hundreds of scientists studying the rainforest to map and understand the region’s biodiversity.
- Ter Steege says the rainforest is in danger of collapse: If the deforestation in Brazil’s Pará state continues at the rate of the year 2000, he warns, “then our models show there will be hardly anything left by 2050.”
- Large trees are dying faster in the Amazon, he said, as they face a greater evaporation demand, which they can no longer meet with the water they extract from the soil, as there are more droughts and less rainfall.
- If the forest collapses, Brazil’s aerial water supply system — and its agriculture — will collapse, Ter Steege says.

‘Five years and no justice’ as trial over Indigenous forest guardian’s killing faces delays (Nov 13 2024)
- Nov. 1 marked the five-year anniversary of the killing of Indigenous forest guardian Paulo Paulino Guajajara and the attempted killing of fellow guardian Laércio Guajajara in an alleged ambush by loggers in the Arariboia Indigenous Territory in the Brazilian Amazon; the suspects haven’t been tried yet.
- Between 1991 and 2023, 38 Indigenous Guajajara were killed in Arariboia; none of the perpetrators have been brought to trial.
- Paulo’s case will be a legal landmark as the first killing of an Indigenous leader to go before a federal jury; as Mongabay reported a year ago, the start of the trial was contingent on an anthropological report of the collective damages to the Indigenous community as a result of the crimes.
- However, the report has yet to be made, given several issues that delayed the trial, including the change of judge, the long time to choose the expert to prepare the report and get the expert’s quote, and the reluctance from the Federal Attorney General’s Office (AGU) to pay for the report.

Amazon deforestation in Brazil plunges 31% to lowest level in 9 years (Nov 10 2024)
- Deforestation in the Brazilian Amazon dropped by 30.6% over the past year, reaching its lowest level since 2015, with 6,288 square kilometers cleared by July 31, 2024.
- Despite the drop in deforestation, fires surged nearly 18-fold in September due to severe drought, with fire hotspots up 70% from the previous year.
- Fires impacted ecosystems across South America, especially in Brazil’s Pantanal and Cerrado. But deforestation also dropped in the Cerrado, falling 25.7%.
- The Amazon faces increasing threats from climate change, deforestation, and degradation, raising concerns about destabilizing rainfall patterns and biodiversity loss.

Brazil calls for ambition at COP but struggles over its own climate policy (Nov 8 2024)
- Brazil is trying to resume its role as a protagonist in the environmental arena by hosting COP30 in 2025 and urging other countries to present ambitious targets to cut emissions.
- However, Luiz Inácio Lula da Silva’s administration failed to openly discuss the country’s nationally determined contribution (NDC) and allocated small budgets for climate transition.
- Experts state that zeroing out deforestation, recovering thousands of hectares of native vegetation and stepping back from oil expansion plans are crucial to meeting Brazil’s commitments.
- UPDATE (11/11/2024): The Brazilian government released its NDC on the evening of Nov. 8, hours after the publication of this story.

New Canadian-backed potash mine under fire from Amazon Indigenous groups (Nov 7 2024)
- For more than a decade, Potássio do Brasil, a Canadian-backed mining company, has tried to exploit the Brazilian Amazon’s potash reserves, despite legal challenges.
- In April, the Amazonas Environmental Protection Institute (IPAAM) granted the company several installation licenses, which authorized the project’s implementation as well as the construction of a road and shipping port.
- According to the Federal Public Prosecutor’s Office (MPF) and Funai, the issuance of these licenses by the Amazonas government was illegal, as the project overlaps with Indigenous lands and many communities were not consulted.
- Many Mura residents, most of whom are concerned about the impact the project will have on the environment and their livelihoods, say the company did not consult them and instead co-opted leaders and falsified documents.

Brazil sets a date to remove illegal miners from Munduruku land, more details await (Nov 6 2024)
- There’s a planned start date to remove illegal gold miners from the Munduruku Indigenous territory, where they have long decimated the Munduruku people’s health and the Amazon ecosystem with mercury contamination, prosecutors share with Mongabay.
- The date and removal operation remains confidential, with government sources gathering data on the areas most affected in the region. The government may share more information during a press briefing in early November, while some news sites suggest the operation will begin in a few days and involve the defense ministry.
- The Supreme Court and Indigenous peoples have called for the removal of the miners from the region for years, to little avail. Meanwhile, other sources say the government had to prioritize crises in other Indigenous lands like the Yanomami territory.
- According to a researcher, the expulsion of gold miners from another Munduruku territory, the Sawré Muybu Indigenous land, cannot begin until the president recognizes the territory.

Report reveals how environmental crime profits in the Amazon are laundered (Nov 5 2024)
- A recent report from the FACT Coalition analyzed 230 cases of environmental crime in Amazon countries over the past decade to better understand how crimes are committed and how the associated profits are laundered.
- It found that the U.S. is the most common foreign destination for the products and proceeds of environmental crimes committed in the Amazon region.
- The most popular way to launder money involves the use of shell and front companies, and corruption was the single most prevalent convergent crime mentioned.
- Of the cases analyzed, only one in three appears to have included a parallel financial investigation.

Brazil researchers boost timber traceability with new chemical analysis (Nov 4 2024)
- Brazilian researchers have opened a new front in the search for a reliable timber tracking system by using chemical analysis to determine where a tree was grown.
- The technique relies on identifying a wood sample’s chemical signature, which can then be matched against various known soil profiles to narrow down its origin.
- As the technology evolves, the researchers say they hope to combine it with stable isotope analysis to increase the precision of timber tracking.
- Most timber provenance inspections in Brazil rely on public documents whose information can easily be faked by illegal loggers.

JBS broke its own rules while buying cattle from deforested areas in Pantanal (Oct 31 2024)
- JBS, the world’s largest meatpacking company, has over the last five years been buying cattle from farms that were caught illegally deforesting Brazil’s Pantanal wetlands despite the company’s claims of environmental responsibility.
- An Unearthed investigation found that JBS suppliers cleared vast areas of the Pantanal wetlands in the past five years, with Fazenda Querência being the largest deforester, having cleared an area half the size of Paris.
- JBS has repeatedly violated its own zero-deforestation policies by continuing to purchase cattle from farms under embargo for illegal deforestation.
- The expansion of agribusiness, especially the demand for cattle and the introduction of invasive species like brachiaria grass, is threatening the Pantanal’s unique biodiversity and its ability to recover naturally from drought and wildfires.

Inclusive tracking and recognition of area-based conservation helps people & planet (commentary) (Oct 30 2024)
- The world needs to embrace an inclusive approach to recognizing and tracking area-based conservation, a new op-ed by a group of researchers argues.
- Momentum has been growing around establishing and tracking protected areas (PAs) and Other Effective area-based Conservation Measures (OECMs) to achieve 30×30 conservation goals, but a wide variety of such efforts occur beyond these, and are underrepresented in global databases: the authors found >40% of the land in Amazon countries is governed with conservation potential or intention, a significantly larger percentage than is reported in the official database.
- “We advise researchers, donors, and decision-makers to consider and inventory a broader scope of area-based conservation and more diverse actors than they currently do. This approach can enhance research, conservation planning, funding allocation, and program strategies to achieve national conservation targets,” the researchers write.
- This article is a commentary. The views expressed are those of the authors, not necessarily Mongabay.

Deforestation plunges but environmental threats remain as Colombia hosts COP16 (Oct 21 2024)
- As global leaders, experts, activists and Indigenous voices meet this October in the Colombian city of Cali at the U.N. Biodiversity Conference, COP16, missteps and successes within President Gustavo Petro’s environment agenda are watched closely.
- COP16 occurs two years after the country’s first-ever left-wing president was sworn in, pledging to turn Colombia into “a leader in the protection of life,” as his four-year plan centers on energy transition, Indigenous causes and tackling climate change.
- But while praised internationally for his efforts to promote conservation, shift away from fossil fuels and surround himself with green-abiding authorities, Petro remains under pressure, as many of his environmental proposals are still on paper, upholding Colombia’s long-lasting socioenvironmental struggles.
- Experts attribute a lack of sufficient environmental resolutions to various factors, including a Congress resistant to government initiatives, challenges in curbing deforestation and Colombia’s status as the most dangerous country for environmental defenders, as highlighted by recent reports.

Extreme drought wrecks rivers and daily life in Amazon’s most burnt Indigenous land (Oct 18 2024)
- Almost 20% of the Kayapó Indigenous Territory has burned in this year’s Amazon drought, the worst ever recorded in Brazil.
- The land has for years been subjected to illegal mining, cattle ranching and burning of forests, degrading both the soil and rivers and significantly disrupting the way of life for the Mebêngôkre-Kayapó people.
- The Indigenous inhabitants now confront a growing crisis as wildfires and drought threaten their lands, particularly along the Riozinho River.
- According to ecologist Rodolfo Salm, who has worked with the Kayapó since 1996, fire has now surpassed illegal logging as the greatest danger to the region.

PICTURES OF THE AMAZON RAINFOREST