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

From Japan to Brazil: Reforesting the Amazon with the Miyawaki method (Jan 24 2023)
- Reforestation using the Miyawaki method seeks to restore nature to its original state with results that can be seen in around six years.
- Miyawaki works around three concepts: trees should be native, several species should be randomly planted, and the materials for the seedlings and the soil should be organic.
- The method is suitable for urban areas, which gives it a significant capacity to connect human beings with nature, with benefits for the health and well-being of the population.
- Different from other reforestation methods that may seek a financial return, like agroforestry, the motivation of the Miyawaki method is purely ecological.

Dammed, now mined: Indigenous Brazilians fight for the Xingu River’s future (Jan 12 2023)
- Canadian mining company Belo Sun wants to build a huge gold mine in the Big Bend of the Xingu River in the Brazilian Amazon, but faces opposition from Indigenous communities.
- In addition to the environmental impacts, experts warn of the risk of the proposed tailings dam rupturing, which could flood the area with 9 million cubic meters (2.4 billion gallons) of toxic waste.
- The same region is already suffering the impacts of the Belo Monte hydroelectric dam, which diverts up to 85% of the flow of the Xingu River, leading to a mass decline in fish that traditional riverside dwellers and Indigenous people rely on.  
- The Belo Sun project was legally challenged last year, prompting supporters to harass and intimidate those who oppose the mine’s construction; tensions in the region remain high.

Deforestation ‘out of control’ in reserve in Brazil’s cattle capital (Jan 11 2023)
- Forest destruction has ravaged Triunfo do Xingu, a reserve earmarked for sustainable use that has nonetheless become one of the most deforested slices of the Brazilian Amazon.
- Fires burned swaths of the reserve in recent months and forest clearing has surged, with satellite images showing even the most remote remnants of old-growth rainforest were whittled away last year.
- Advocates say the forest is mainly giving way to cattle pasture, although illegal mining and land grabbing are gaining ground.
- The destruction, facilitated by lax environmental regulation, is placing pressure on nearby protected areas and undermining agroforestry efforts in Triunfo do Xingu, advocates say.

Venezuela’s Yapacana National Park suffering increasing mining deforestation: report (Jan 11 2023)
- Satellite imagery analyzed by NGO Amazon Conservation revealed that illegal mining operations in Yapacana National Park, located in the Venezuelan state of Amazonas, are clearing protected forest much faster than previously thought.
- Over 750 hectares (1,870 acres) of deforestation took place between 2021 and 2022 in the mining area of the park.
- Although law enforcement carried out raids in the area last December, many experts believe the problem will persist amid government complacency.

Weakening of agrarian reform program increases violence against settlers in Brazilian Amazon (Jan 10 2023)
- Residents of a landless workers’ settlement in Anapu, Pará state, in Brazil’s Amazon region, accuse the federal government of favoring large landowners, land-grabbers and corporations at the expense of poor and landless peasants.
- This year, the settlers have already suffered three attacks by landowners, with houses set on fire and a school destroyed.
- In 2021, Incra, the Brazilian federal agency responsible for addressing the country’s deep inequalities in rural land use and ownership, made an agreement with the mining company Belo Sun, which ceded 2,400 hectares (5,930 acres) of an area reserved for agrarian reform for gold exploration in exchange for equipment and a percentage of mining profits.
- In protest, landless peasants occupied one of the areas included in the agreement; since then, they have been threatened and intimidated by Belo Sun supporters and armed security guards hired by the mining company.

Series of small dams pose big cumulative risk to Amazon’s fish and people (Jan 3 2023)
- Small hydropower plants and small-scale fish farming in the Brazilian Amazon basin are often thought to cause negligible environmental harm, yet a new study reveals their cumulative damage is greatly underestimated and can be more impactful than large dams.
- Dwindling fish populations caused by the construction of thousands of small dams has impacted the livelihoods of millions of Indigenous and riverside people who depend on fishing for food, income and culture.
- Small hydropower plants and aquaculture farming are encouraged through economic incentives, simple licensing procedures, and loose requirements for environmental impact assessments before construction.
- More than 350 dam proposals in the Amazon basin are under consideration and 98 medium-sized dams will be prioritized in Brazil as of next year, ensuring the construction of hydropower plants will continue.

What happened in the world’s rainforests in 2022? (Dec 29 2022)
- There were some hopeful developments for tropical rainforest conservation in 2022.
- But the outlook for tropical forests nonetheless remains tenuous.
- The following is a look at some of the major tropical rainforest storylines and developments in 2022.

In Brazil’s Amazon, land grabbers scramble to claim disputed Indigenous reserve (Dec 29 2022)
- The Apyterewa Indigenous Territory has been under federal protection since 2007, but in recent years has become one of the most deforested reserves in Brazil, as loggers, ranchers and miners have invaded and razed swaths of forest.
- As President Jair Bolsonaro prepares to leave office, land grabbers are rushing to “deforest while there is still time,” advocates say, with forest clearing in Apyterewa on track to hit new highs this year.
- The surge in invasions has aggravated a decades-long tussle for land between Indigenous people and settlers, who first started trickling into Apyterewa in the 1980s and have since built villages, schools and churches within the reserve.
- The Parakanã people say the outsiders, new and old, are polluting their water sources, depleting forest resources, and threatening their traditional way of life.

Amazon’s tallest tree at risk as deforestation nears (Dec 28 2022)
- Paru State Forest in the state of Pará was Brazil’s fifth-most deforested conservation unit in October, sparking concern for the region’s giant trees — including the tallest in the Amazon.
- The Paru State Forest is the world’s third-largest sustainable-use tropical forest reserve and, together with other conservation units in the region, belongs to a 22 million-hectare (54.3 million-acre) protected mosaic known as the Calha Norte of the Amazon River.
- Deforestation caused by cattle ranchers, illegal land-grabbers and gold miners is advancing in and around the conservation unit, which experts say shouldn’t be happening due to the region’s protected status.
- A new advisory board was formed this November to protect the Paru State Forest for the next two years by monitoring the use of natural resources and deforestation in the area.

‘Panic’ sets in as armed groups occupy, deforest Colombian national park (Dec 12 2022)
- Once covering an expanse of more than 2,140 square kilometers (826 square miles) of the Colombian Amazon Rainforest, Tinigua National Natural Park has lost 29% of its forests over the past 20 years; the majority of this loss has occurred since 2018.
- Satellite data and monitoring suggest forest loss has kept a quick pace in 2022.
- Authorities say illegal cattle ranching, coca growing and land-grabbing are driving deforestation in the park, much of it reportedly done at the hands of armed groups affiliated with FARC dissident factions.
- Local communities have also reportedly been threatened by these groups.

PICTURES OF THE AMAZON RAINFOREST