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

Pasture replaces large tract of intact primary forest in Brazilian protected area (May 13 2022)
- Satellites have detected forest clearing within the Triunfo do Xingu Environmental Protection Area (APA) this year, a legally protected area of Brazil’s Amazon rainforest.
- Despite its status, 35% of the primary (or old-growth) forest within the APA was lost between 2006 and 2021, making it one of the most deforested slices of the Brazilian Amazon.
- The APA was created in 2006 to serve as a buffer for vulnerable surrounding areas, such as the Apyterewa Indigenous Territory and the massive Terra do Meio Ecological Station, but deforestation has spilled over into both.
- Deforestation in the region is largely driven by cattle ranching, but land grabbing and mining have also increased in recent years, with invaders emboldened by the rhetoric and policies of the current government.

In Brazilian Amazon, Indigenous lands stop deforestation and boost recovery (May 13 2022)
- A new study has confirmed that the best-preserved, and recovering, parts of the Brazilian Amazon are those managed by traditional communities or inside conservation units.
- Between 2005 and 2012, deforestation rates were 17 times lower in Indigenous territories than in unprotected areas of the Amazon; in conservation units and lands managed by Quilombolas, the descendants of runaway Afro-Brazilian slaves, deforestation rates were about six times lower than in unprotected areas.
- The study also shows that officially recognized Indigenous and Quilombola territories saw forest regrowth at rates two and three times higher, respectively, than in unprotected areas.
- But the process of officially recognizing Indigenous lands has stalled under the government of President Jair Bolsonaro, which is instead pushing legislation that would open up Indigenous territories to mining and other exploitative activities.

Amazon deforestation surges in April (May 6 2022)
- Deforestation in the Brazilian Amazon exceeded 1,000 square kilometers in April, the highest total since 2008 and roughly twice the level of April 2021, according to data released today by Brazil’s national space research institute INPE.
- The loss — which only accounts for the first 29 days of the month — put deforestation in the Brazilian Amazon through the first four months of 2022 at 1,953 square kilometers as the region heads into the peak deforestation season.
- Last year deforestation topped 13,000 square kilometers for the first time since 2006.
- Scientists have warned that the Amazon may be approaching a tipping point where vast areas of rainforest transition to a woody savanna.

A new index measures the human impacts on Amazon waters (May 5 2022)
- Based on the best scientific data available, the unprecedented Amazon Water Impact Index draws together monitoring and research data to identify the most vulnerable areas of the Brazilian Amazon.
- According to the index, 20% of the 11,216 Brazilian Amazon micro basins have an impact considered high, very high or extreme; half of these watersheds are affected by hydroelectric plants.
- The same index points out that 323 of the 385 Indigenous Lands in the Brazilian Amazon face a medium to low impact, which demonstrates the fundamental role of these areas in protecting the aquatic ecosystems of the Amazon.
- The Amazon River Basin covers 7 million square kilometers (2.7 million square miles) and contains 20% of all freshwater on the Earth’s surface; still, little is known about the impacts of increased human activity on aquatic ecosystems.

Putin’s financial interest in Brazil’s Amazon highways (commentary) (May 4 2022)
- Rosneft, a giant Russian government oil and gas company, has bought drilling rights to 16 blocks in the vast area of intact rainforest in the western part of Brazil’s Amazon region. A planned highway would give access directly to three of these blocks, and branch roads would be likely to be built to the other Rosneft blocks, opening the area to invasion by landgrabbers, squatters, loggers and others.
- Vladimir Putin appointed as Rosneft’s CEO a close friend who is considered to be the most powerful person in Russia after Putin himself. Putin views Rosneft as his personal property according to the exiled oligarch who had formerly been “Putin’s banker.”
- Building the BR-319 and AM-366 highways would financially benefit Putin’s associates (and either directly or indirectly Putin himself). Rosneft is capable of influencing Brazilian authorities to prioritize these highways. It is unknown what was discussed about “energy” when Brazilian President Jair Bolsonaro met with Putin in Moscow for three hours just before the invasion of Ukraine.
- This post is a commentary. The views expressed are those of the author, not necessarily Mongabay.

2021 tropical forest loss figures put zero-deforestation goal by 2030 out of reach (Apr 28 2022)
- The world lost a Cuba-sized area of tropical forest in 2021, putting it far off track from meeting the no-deforestation goal by 2030 that governments and companies committed to at last year’s COP26 climate summit.
- Deforestation rates remained persistently high in Brazil and the Democratic Republic of Congo, home to the world’s two biggest expanses of tropical forest, negating the decline in deforestation seen in places like Indonesia and Gabon.
- The diverging trends in the different countries show that “it’s the domestic politics of forests that often really make a key difference,” says leading forest governance expert Frances Seymour.
- The boreal forests of Eurasia and North America also experienced a spike in deforestation last year, driven mainly by massive fires in Russia, which could set off a feedback loop of more heating and more burning.

Brazil bill seeks to redraw Amazon borders in favor of agribusiness (Apr 25 2022)
- A new bill before Brazil’s Congress proposes cutting out the state of Mato Grosso from the country’s legally defined Amazon region to allow greater deforestation there for agribusiness.
- Under the bill, known as PL 337, requirements to maintain Amazonian vegetation in the state at 80% of a rural property’s area, and 35% for Cerrado vegetation, would be slashed to just 20% for both.
- The approval of the bill would allow for an increase in deforestation of at least 10 million hectares (25 million acres) — an area the size of South Korea — and exempt farmers from having to restore degraded areas on their properties.
- Environmental law specialists warn that the departure of Mato Grosso from under the administrative umbrella of the Legal Amazon would set off a domino effect encouraging the eight other states in the region to push for similar bills.

Canadian miners get high-level lobbying boost for Brazilian Amazon projects (Apr 20 2022)
- Canadian bank Forbes & Manhattan appears to be aided in pushing its mining interests in Brazil thanks to lobbying efforts by an old army acquaintance of the country’s vice president.
- F&M has been trying to secure environmental licenses for two of its companies, Belo Sun and Brazil Potash, for more than 10 years; both companies’ projects have been criticized for threatening Indigenous groups and traditional riverside communities in the Amazon.
- But F&M has managed to secure several private meetings with top government officials, which all appear to feature the same individual acting in a consulting or advisory role: Cláudio Barroso Magno Filho, a retired brigadier general in the Brazilian Army.
- Barroso Magno attended the military academy alongside Hamilton Mourão, who in 2019 took office as Brazil’s vice president in the administration of President Jair Bolsonaro.

History on the walls: Graffiti brings Manaus’s Indigenous roots to light (Apr 19 2022)
- Graffiti artists are painting murals recounting the history of Indigenous people and honoring their culture in the capital of Amazonas, the Brazilian state with the largest Indigenous population.
- Indigenous community leaders say they hope the movement will increase the visibility of Indigenous people living in cities, who often face poverty, housing insecurity and stigma that discourages many from maintaining their culture and identity.
- Fearing cultural erasure, Indigenous activists are urging Indigenous people to embrace their ancestry and identify themselves as Indigenous in Brazil’s next census, expected to begin in August 2022.
- As Indigenous people in cities reclaim their identities, occupying public spaces through street art is playing a key role in the fight to make Indigenous people in urban areas more visible.

Amazon deforestation dips slightly in March, but remains high (Apr 9 2022)
- Deforestation in the Brazilian Amazon amounted to 312 sq km in March, a 15% decline over March 2021.
- Despite the drop however, deforestation for the first quarter of 2022 reached 941 square kilometers, the highest level for a first quarter since 2018.
- Deforestation in the Brazilian Amazon has been trending higher since 2012.
- The Brazilian Amazon accounts for nearly two-thirds of the Amazon rainforest.

PICTURES OF THE AMAZON RAINFOREST