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

The force is strong with space lasers helping researchers map the Amazon in 3D (Oct 4 2022)
- Since 2018, the GEDI mission has employed lasers on the International Space Station to measure the biomass density of forests on Earth.
- The information helps us understand how deforestation contributes to worsening climate change via increases in atmospheric concentration of carbon dioxide.
- In the Amazon rainforest, data from the mission have highlighted specific areas that could benefit from carbon-based conservation.

The Amazon will reach tipping point if current trend of deforestation continues (Oct 3 2022)
- A report by the Amazon Network of Georeferenced Socio-Environmental Information (RAISG) claims that 26% of Amazon forests have transformed irreversibly and show high levels of degradation.
- The savannization of the Amazon is already visible in Brazil and Bolivia, while Ecuador, Colombia and Peru seem to be heading in the same direction.
- The report also seeks to make visible the role of Indigenous peoples in protecting the Amazon, and to ensure that Indigenous people are at the center of the fight against climate change.

Cutting down the Amazon does not build prosperity for most Brazilians (Sep 29 2022)
- Deforestation proponents in Brazil routinely argue that cutting down the Amazon is an effective way to alleviate poverty. This is especially the case with the Bolsonaro administration, which issued an official statement to the 2021 United Nations Climate Change Conference stating that “where there is a lot of forest there is also a lot of poverty.”
- Ahead of Brazil’s latest election, a group of us led by Darren Norris of the Federal University of Amapá decided to see what the data says about links between deforestation and poverty in the Amazon.
- We found no association between forest loss and these economic indicators. Indeed, the economic indicators for municipalities with less than 40% forest cover in 1986 were no different than those of similar municipalities with more than 60% forest cover from 1986 to 2019.
- The finding thus suggests that “deforestation does not necessarily generate transformative and equitable food production systems or lead to poverty alleviation,” as we write.

Road network spreads ‘arteries of destruction’ across 41% of Brazilian Amazon (Sep 22 2022)
- A groundbreaking study using satellite data and an artificial intelligence algorithm shows how the spread of unofficial roads throughout the Amazon is driving widespread deforestation.
- One such road is on the verge of cutting across the Xingu Socioenvironmental Corridor, posing a serious risk of helping push the Amazon beyond a crucial tipping point.
- Unprotected public lands account for 25% of the total illegal road network, with experts saying the creation of more protected areas could stem the spread and slow both deforestation and land grabs.
- Officially sanctioned roads, such as the Trans-Amazonian Highway, also need better planning to minimize their impact and prevent the growth of illegal offshoots, experts say.

How close is the Amazon tipping point? Forest loss in the east changes the equation (Sep 20 2022)
- Scientists warn that the Amazon is approaching a tipping point beyond which it would begin to transition from a lush tropical forest into a dry, degraded savanna. This point may be reached when 25% of the forest is lost.
- In a newly released report, the Monitoring of the Andean Amazon Project (MAAP) estimates that 13.2% of the original Amazon forest biome has been lost due to deforestation and other causes.
- However, when the map is divided into thirds, it shows that 31% of the eastern Amazon has been lost. Moisture cycles through the forest from east to west, creating up to half of all rainfall across the Amazon. The 31% figure is critical, the report says, “because the tipping point will likely be triggered in the east.”
- Experts say the upcoming elections in Brazil could have dramatic consequences for the Amazon, and to avert the tipping point we must lower emissions, undertake ambitious reforestation projects, and build an economy based on the standing forest. Granting and honoring Indigenous land tenure and protected areas are also key strategies.

More droughts are coming, and the Amazon can’t keep up: Study (Sep 16 2022)
- Up to 50% of rainfall in the Amazon comes from the forest itself, as moisture is recycled from the trees to the atmosphere.
- In severe droughts, when the forest loses more water to evaporation than it receives from rain, the trees begin to die. For every three trees that die due to drought in the Amazon rainforest, a fourth tree, even if not directly affected by drought, will also die, according to a new study.
- As trees are lost and the forest dries up, parts of the Amazon will rapidly approach a tipping point, where they will transition into a degraded savanna-like ecosystem with few to no trees.
- The southern and southeastern Amazon are the most vulnerable regions to tipping. Here, deforestation and fires are at their most extreme, driven largely by cattle ranching and soy farming.

Bolsonaro trails in polls, but his base in Congress looks likely to persist (Sep 13 2022)
- With Brazil’s presidential election scheduled for Oct. 2, environmental activists have expressed hope that a turning point in favor of nature could be just weeks away if Jair Bolsonaro loses.
- But two-thirds of the current lower house of Congress voted for anti-environmental bills, and experts predict that the profile of the lawmakers will remain right-wing and pro-agribusiness.
- Deforestation in the Amazon rose to its highest levels in 10 years under Bolsonaro, who vowed to open up the rainforest to agriculture and mining.
- However, experts say a greener agenda could be possible depending on who is appointed the next lower and upper house presidents, a decision that will be made early next year.

Amazon deforestation in Brazil booms in August (Sep 9 2022)
- Rainforest destruction in the Brazilian Amazon jumped 11% in August with deforestation reaching 1,661 square kilometers (641 square miles) — an area more than 28 times the size of Manhattan — according to data released today by Brazil’s national space research agency, INPE.
- The tally brings rainforest clearing detected in the Brazilian Amazon since the beginning of the year by INPE’s deforestation alert system to 7,135 square kilometers, the highest on record dating back to 2008.
- About 80% of August’s deforestation occurred in just three states: Para (41%), Mato Grosso (20%), and Amazonas (19%).
- Deforestation in the Brazilian Amazon has been trending higher since 2012 and has especially accelerated since 2019, when Jair Bolsonaro became president.

Illegal logging and trade in fine wood threaten Wampis communities in the Peruvian Amazon (Sep 9 2022)
- More than 20,000 board feet of protected forest species, such as cedar and mahogany, are being lost from forests inhabited by Wampis communities every month, according to estimates by community leaders.
- The extraction and sale of these fine woods have increased since the start of 2022 after two Wampis communities obtained permits for the use of certain forest resources.
- According to Wampis leaders, since the issuing of the permits to the two communities, loggers have been able to cut down and transport cedar and mahogany wood, despite these trees being protected species.

Report lists Indigenous territories under greatest pressure in the Amazon (Sep 5 2022)
- Apyterewa, the territory of the Parakanã people, continues to be the main target of deforestation by land grabbers among the Indigenous territories of the Amazon, a report by Imazon shows.
- The advance of land grabbing in the area known as the “deforestation belt” is used as a form of political pressure for reducing and questioning legally recognized areas.
- Despite increasing pressure, Indigenous territories still have the lowest deforestation rate among protected areas, proving their effectiveness as a preservation policy.
- Indigenous representatives and civil society advocates criticize the federal government for reducing vigilance and putting forward bills to explore Indigenous land.

PICTURES OF THE AMAZON RAINFOREST