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

Crimes against the Amazon reverberate across Brazil, analysis shows (Aug 31 2022)
- Crimes associated with illegal logging, mining and other illicit activities in the Brazilian Amazon are being felt in 24 of Brazil’s 27 states, a new report shows.
- Records of more than 300 Federal Police operations between 2016 and 2021 show that crimes such as tax evasion, money laundering, corruption and wildlife trafficking are reverberating far beyond the rainforest.
- Deforestation is at the center of the criminal economy in the Amazon, driving four main illegal activities: logging, mining, occupation of public lands, and environmental violations associated with agriculture.
- Nearly half of the police operations investigated crimes that occurred in protected areas in the Amazon, including 37 Indigenous territories.

Venezuelan Amazon deforestation expands due to lawlessness, mining, fires: Reports (Aug 31 2022)
- Multiple recent reports show that deforestation has greatly increased in Venezuela’s Amazonian states of Bolívar and Amazonas, largely due to illegal mining, expanded agriculture and fires.
- Venezuelan protected areas have been especially hard hit, with illegal incursions and major deforestation occurring inside Caura, Canaima and Yapacana national parks.
- Soaring deforestation rates are blamed partly on Colombian guerrillas operating illegally within Venezuela’s borders, an invasion that one report alleges has been supported by the government of Venezuelan President Nicolás Maduro.
- Forest loss has been well confirmed via satellite, while ground truthing has been obtained via firsthand accounts.

Indepedent watchdog confirms rampant deforestation in the Amazon (Aug 31 2022)
- Data from independent forest monitoring group Imazon has confirmed that deforestation in Earth’s largest rainforest is on track to approach the highest level in 15 years.
- Imazon’s monthly deforestation alert system detected 10,781 square kilometers of forest clearing in the Brazilian Amazon betwen August 2021 to July 2022, a 3% rise over the same period last year when forest destruction reached the highest level since 2006.
- Imazon’s update came shortly after INPE, Brazil’s national space research institute, published its own deforestation alert-based data.
- Deforestation in the Brazilian Amazon has been on an upward trend since 2012.

Brazil miner sees Indigenous land as ripe for exploration if protections expire (Aug 30 2022)
- Mining company Oxycer has filed five applications to prospect for gold in the Piripkura Indigenous Territory, in anticipation of restrictions being lifted this October.
- The territory is home to two of the last three surviving Piripkura individuals, who live in voluntary isolation and already face threats from invasions of their territory by illegal loggers and cattle ranchers.
- Mining in Indigenous territories is currently illegal in Brazil, which is why the Federal Public Ministry is pursuing lawsuits to scupper mining requests being filed with the National Mining Agency (ANM).
- However, the ANM continues to accept and register these applications for what’s clearly an illegal activity, though it’s unclear if the agency has approved any of them yet.

Bolsonaro agenda gets a lift from dominance of ‘new right’ in Congress (Aug 29 2022)
- A ranking of federal lawmakers in Brazil based on their legislative and voting records has highlighted the rise of a “new right” that’s firmly behind President Jair Bolsonaro’s agenda of rolling back environmental and Indigenous protections.
- The Ruralômetro scale, developed by investigative news outlet Repórter Brasil, shows at least 351 out of 513 members of the Chamber of Deputies scored unfavorably on socioenvironmental issues.
- Among the legislation they helped draft or voted in favor of include those that weaken environmental law enforcement, favor predatory economic activities, undermine labor protections, hamper access to social benefits, and hinder agrarian reform.
- Joênia Wapichana, the first Indigenous woman elected to the Chamber of Deputies, said the strengthening of this “ruralist” base has forced environmentalists on the defensive, without much room to advance their own bills.

Forest fires are getting worse, 20 years of data confirm (Aug 17 2022)
- Fires are now causing an additional 3 million hectares (7.4 million acres) of tree cover loss per year than they did in 2001, according to a newly released Global Forest Watch analysis that examined fires that burn all or most of a forest’s living overstory trees.
- The majority of all fire-caused tree cover loss in the past 20 years (nearly 70%) occurred in boreal regions. Although fires are naturally occurring there, they are now increasing at an annual rate of 3% and burning with greater frequency and severity and over larger areas than historically recorded.
- Fires are not naturally occurring in tropical rainforests, but in recent years, as deforestation and climate change have degraded and dried out intact forests, fires have been escaping into standing tropical rainforests. GFW findings suggest fires in the tropics have increased by roughly 5% per year since 2001.
- Researchers say there is no “silver bullet” solution for forest fires, but experts call for more spending on planning and preparation.

Amazon cloud forests need protection (commentary) (Aug 15 2022)
- Where the Andes meet the Amazon, you will find one of the earth’s richest and most important biomes but its role has been largely overlooked in our efforts to mitigate climate change impacts, argues Enrique G. Ortiz of the Andes Amazon Fund.
- After 40 years working in tropical forests, Ortiz says the Amazon cloud forest is his favorite type of forest. In this commentary, he makes the case for why their protection should be a priority for conservation efforts.
- This article is a commentary. The views expressed are those of the author, not necessarily of Mongabay.

Amazon deforestation on pace to roughly match last year’s rate of loss (Aug 12 2022)
- Deforestation in Earth’s largest rainforest is on track to rival last year’s 15-year-high according to data released today by the Brazilian government.
- INPE, Brazil’s national space research institute, today published figures from its DETER deforestation alert system, which tracks forest clearing on a near-real time basis. INPE’s system detected 8,590 square kilometers of deforestation between August 1, 2021 and July 31, 2022, 2.3% lower than the previous year, when deforestation hit the highest level since 2006.
- The area of forest affected by degradation and selected cutting, which is typically a precursor to outright deforestation, climbed 15.6% year over year.
- 2022’s tally represents an area nearly the size of Puerto Rico or Cypress. But the actual area of forest loss over the past 12 months is significantly higher: INPE is expected to release its findings from analysis of high resolution satellite imagery in October or November.

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.”

PICTURES OF THE AMAZON RAINFOREST