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

Violence persists in Amazon region where Pereira and Phillips were killed (Aug 2 2022)
- Armed illegal gold miners on July 15 threatened government rangers near the site where British journalist Dom Phillips and Brazilian Indigenous expert Bruno Pereira were killed in June.
- Days after the threats, federal prosecutors charged three men in the killing of Phillips and Pereira, but activists and lawmakers say the investigation needs to be expanded to identify the possible involvement of criminal organizations.
- Activists say threats against government officials, including Pereira, have happened for decades, but that the situation has grown dire under President Jair Bolsonaro.
- The government’s weakening of environmental agencies and Bolsonaro’s anti-Indigenous rhetoric have created a sense of impunity, emboldening criminals in the Amazon to retaliate against activists and environmentalists who expose their illicit activities, experts say.

Organized crime drives violence and deforestation in the Amazon, study shows (Aug 1 2022)
- Increasing rates of both deforestation and violence in the Brazilian Amazon are being driven by sprawling national and transnational criminal networks, a study shows.
- Experts say criminal organizations engaged in activities ranging from illegal logging to drug trafficking often threaten and attack environmentalists, Indigenous people, and enforcement agents who attempt to stop them.
- In 2020, the Brazilian Amazon had the highest murder rate in Brazil, at 29.6 homicides per 100,000 habitants, compared to the national average of 23.9, with the highest rates corresponding to municipalities suffering the most deforestation.
- Experts say the current government’s systematic dismantling of environmental protections and enforcement agencies has emboldened these criminal organizations, which have now become “well connected, well established and very strong.”

From agribusiness to oil to nuclear power and submarines: welcome to anti-environmental Putin-Bolsonaro alliance (commentary) (Aug 1 2022)
- Brazil’s dependence on Russian fertilizers has contributed to Jair Bolsonaro’s friendly relationship with Vladimir Putin as well as environmental impacts in the South American nation.
- In this editorial Nikolas Kozloff, an American academic, author and photojournalist, reviews some of the implications of the growing ties between the two leaders, including deforestation in the Amazon, extractive industries, and infrastructure projects.
- This article is a commentary. The views expressed are those of the author, not necessarily of Mongabay.

As the Amazon burns, only the weather can ward off a catastrophe, experts say (Jul 26 2022)
- The Brazilian Amazon saw the highest number of fires for the month of June in 15 years, with 2,562 major fires detected, an increase of 11.14% over 2021.
- The first half of the year had 7,533 major fires, the most since 2019, according to data from the national space research institute.
- On June 23, the Brazilian government issued a decree banning the use of fires to manage forests throughout the country for the next 120 days.
- Experts say they’re skeptical about this ban, noting that similar measures failed to stop the burning in previous years, and say the weather is the only thing that can help curb the increase in fires as the dry season unfolds.

Brazil’s new deforestation data board sparks fear of censorship of forest loss, fires (Jul 22 2022)
- A new council set by the Brazilian government to vet deforestation and forest fire data from the country’s space agency has been widely slammed as a political ploy to aid President Jair Bolsonaro’s reelection bid.
- The National Institute of Space Research (INPE) has provided and analyzed deforestation and forest fire data in the Amazon since 1988 and is globally renowned for its monitoring expertise, but was left out of the new council.
- The Bolsonaro government has questioned the credibility of INPE’s data since taking office in 2019, drawing outrage from scientists and researchers for claiming that data showing a spike in deforestation under Bolsonaro was false.
- Experts have raise concerns that the new council could prevent the release of annual deforestation data, scheduled at the same time as this year’s elections, that are expected to show an alarming increase in both forest loss and fires.

First-of-its-kind freshwater mangroves discovered in Brazil’s Amazon Delta (Jul 20 2022)
- Researchers on an expedition in the Amazon River Delta have found mangroves growing in freshwater — a phenomenon never before documented in deltas or coastal mangroves anywhere else in the world.
- The mangroves, overlooked by previous satellite mapping efforts, increase the known area of mangroves in the region by 20%, or an additional 180 square kilometers (70 square miles).
- Mangroves are a more effective carbon sink than other types of tropical forest, with more than 8% of all carbon stocks worldwide held in Brazil’s mangroves.
- Despite their many ecosystem services, mangroves are not well protected or funded in Brazil.

$245-million initiative to create and maintain protected areas in Colombia (Jul 14 2022)
- Heritage Colombia is a $245-million initiative to support the creation, expansion and improvement of 32 million hectares (nearly 80 million acres) of protected land and marine areas in the country over the next decade.
- It’s a Project Finance for Permanence (PFP) initiative, meaning that conservation funding was secured from the public and private sector for wide-reaching, long-term projects.
- If Heritage Colombia is successful, the country will see 26% of its land territory and 30% of its oceans under protection, meeting some of its 30×30 commitment eight years early.

Amazon deforestation is off to the fastest start to a year since 2008 (Jul 8 2022)
- Deforestation in the Brazilian Amazon is off to the fastest start for the first half of any year since 2008 according to government data published today.
- Deforestation alert data from Brazil’s national space research institute INPE shows that 3,988 square kilometers of forest have been cleared within the Brazilian Amazon since January 1, a 17 percent rise over last year.
- Deforestation in the Brazilian Amazon reached a 15-year high in 2021.

Habitat loss, climate change send hyacinth macaw reeling back into endangered status (Jul 4 2022)
- The hyacinth macaw, the world’s largest flying parrot, is closer to return to Brazil’s endangered species list, less than a decade after intensive conservation efforts succeeded in getting it off the list.
- The latest assessment still needs to be made official by the Ministry of the Environment, which is likely to publish the updated endangered species list next year.
- Conservation experts attribute the bird’s decline to the loss of its habitat due to fires in the Pantanal wetlands and ongoing deforestation in the Amazon and Cerrado biomes.
- Climate change also poses a serious threat, subjecting the birds to temperature swings that can kill eggs and hatchlings, and driving heavy rainfall that floods their preferred nesting sites.

Protecting Brazil’s Amazon could be a bargain — if the government were willing to pay (Jul 4 2022)
- A new study shows that conserving 350 million hectares (865 million acres) of the Brazilian Amazon — 83% of the biome — would cost between $1.7 billion and $2.8 billion a year.
- That’s a fraction of the $5.3 billion that the European Union spends every year maintaining its 1 million hectares (2.5 million acres) of protected areas.
- Current protected areas cover 51% of the Brazilian Amazon, which experts say isn’t enough to maintain the biome’s biodiversity and must be expanded.
- While the cost for protecting the Amazon is hundreds of times cheaper, hectare for hectare, than in the EU, it’s much higher than what the Brazilian government allocates for environmental conservation.

PICTURES OF THE AMAZON RAINFOREST