The Amazon Rainforest

Twice the size of India, the Amazon Rainforest occupies almost the entire width of northern South America, from the Atlantic in the east, to the foothills of the Andes mountains in the west. In addition to its 390 billion trees, which makes it an irreplaceable carbon reservoir, it supports at least 10 percent of the world’s animal and plant species. It is dominated by the mighty Amazon River, 6,600 kilometers in length, which has more than 1,100 tributaries as well as the largest number of freshwater fish species in the world.
Amazon Rainforest in Peru
Amazon Rainforest, seen from the Alto Madre de Dios river in Peru. Photo: © Martin St-Amant/(CC BY-SA 3.0)

The Amazon Rainforest is the world’s largest tropical rainforest biome, occupying more than three quarters of the Amazon Basin in South America. It consists of 2.1 million square miles (1.3 billion acres) of moist broadleaf tropical rainforest, much of it dense old-growth forest. 1 Its dense vegetation and tree mass makes it one of the world’s largest and most precious carbon sinks.

In comparison, the Congo Rainforest, the world’s second largest tropical rainforest, occupies around 1.1 million square miles, while rainforests in SE Asia cover less than 900,000 square miles. For more, see: Deforestation in Southeast Asia.

Naturally, therefore, given current levels of global warming, scientists have watched the increasing deforestation of the Amazon Basin with mounting concern. Such forest clearance typically leads to significant greenhouse gas emissions of carbon dioxide, which will only exacerbate the climate crisis facing our planet. 

The Amazon Rainforest is shared by nine different countries: Brazil (58.4 percent), Peru (12.8 percent), Bolivia (7.7 percent), Colombia (7.1 percent), Venezuela (6.1 percent), Guyana (3.1 percent), Suriname (2.5 percent), French Guyana (1.4 percent) and Ecuador (1 percent). 2 Figures from Brazil’s National Space Agency indicate that the deforestation in the Amazon Rainforest has reached its highest point in more than a decade. However, the health of the Amazon ecosystem is a global concern, and needs global response. The United Nations is the obvious forum in which to build a consensus on how to proceed. See also: History of Deforestation.

How Large is the Amazon Rainforest Biome?

The Amazon River drains something like 6.9 million sq km (2.65 million sq mi), or about 40 percent of South America. But the Amazon biome extends beyond the river basin itself, occupying an area about 7.75-8.25 million sq km (3-3.1 million sq miles) in area, of which roughly 80-82 percent is forest. It’s about the same size as the contiguous United States (8,080,464.3 sq km/ 3,119,884.69 sq miles).

Where Are the World’s Rainforests?

Tropical rainforests – which cover 8 percent of the Earth’s land surface – are located in a band around the equator, mostly in the area between the northern Tropic of Cancer and the southern Tropic of Capricorn. This 4,800 km (3,000 mile) wide band is known as the “tropics.” The largest rainforests are found in the Amazon River Basin (South America), the Congo River Basin (western Africa), and in much of southeast Asia (Vietnam, Cambodia, Thailand, Myanmar, Malaysia, Sumatra). Temperate rainforests (typically coniferous or broadleaf forests) are located in the cooler temperate zone. Such locations include: Norway, Scotland, the Pacific coast from northern California to Alaska; Chile, Tasmania and New Zealand.

Why Is The Amazon Rainforest Important?

1. Unique Biodiversity

Amazonia is important because of its unique biodiversity – it’s home to the largest single collection of plants and animal species in the world, with an estimated 390 billion trees divided into 16,000 species. 3 The Amazon accounts for over half the planet’s surviving rainforest, 4 and is home to 1 in 10 of the world’s species 5 or 10 percent of the world’s store of genetic blueprints. This unique South American biome contains (literally) the secrets of life on Planet Earth, including the origins and causes of disease, as well as their antidotes. Studies clearly show that loss of biodiversity increases the risk of disease for humans. 6

According to the U.S. biologist Edward O. Wilson, two-time winner of the Pulitzer Prize: “The worst thing that can happen… is not energy depletion, economic collapses, limited nuclear war, or conquest by a totalitarian government. As terrible as these catastrophes would be for us, they can be repaired within a few generations. The one process… that will take millions of years to correct is the loss of genetic and species diversity by the destruction of natural habitats. This is the folly that our descendants are least likely to forgive us for.” 7

The Amazon’s ecosystem contains a wealth of undiscovered plants, insects and other creatures. In fact, of the millions of species who live in the Amazonian biome, less than 1 percent have been assessed for their pharmacological benefits. 5 Which is why the big pharmaceutical corporations are bioprospecting in the Amazon region for active ingredients to treat cancer, Alzheimer’s, AIDS, malaria and many other diseases.

According to a study published in Economic Botany, Dr. Robert Mendelsohn, an environmental economist at Yale University, and Dr. Michael J. Balick, director of the Institute of Economic Botany at the New York Botanical Gardens, calculate that the minimum number of pharmaceutical drugs remaining to be extracted from the rainforests is 328, with a potential value of $4 billion to the manufacturer and up to $147 billion to society as a whole. Remember – this is a minimum figure. 8

2. Huge Carbon Sink

The Amazon rainforest plays an important role in the carbon cycle and therefore climate change: it acts as a huge carbon sink, thus mitigating the greenhouse effect and reducing the impact of global warming on the Earth.

Note, however, that new research suggests that the ability of Amazonian trees to absorb carbon dioxide is severely limited (50-100 percent) by the phosphorus content of the soil. 9

Alarming rates of deforestation, caused by commercial logging, animal grazing and slash-and-burn agriculture, has led to a significant reduction in forest cover which climate models project could result in a disastrous release of carbon dioxide into the atmosphere with unknown effects on climate change around the world.

“The Amazon forest holds something like 90 billion tons of carbon and if that ends up in the atmosphere it’s not a good thing,” says Thomas Lovejoy, senior fellow at the United Nations Foundation and professor of environmental science at George Mason University. 10

Other studies, which include carbon in the soil as well as in the trees and vegetation, put the figure even higher at 130 billion tons of CO2. 11

3. Creates Its Own Water Cycle

The Amazon bioregion is a naturally wet and warm place that generates a huge amount of evapotranspiration (the combined processes of evaporation and transpiration). Plants and trees pull up water from the earth which they then transpire into the atmosphere where it cools the surrounding air before rising to form rain clouds. These rain clouds block sunlight, cooling the region as a whole, while also recycling the moisture through their rainfall. See also: How Do Clouds Affect Climate?

A key benefit of this constant water cycle is the massive outflow of the Amazon River into the Atlantic Ocean. This outflow – equivalent to 219 million one-litre bottles of water every second – contains a huge amount of nutrients that fertilize a vast expanse of surrounding water and boosts the growth of phytoplankton – a key element in the ecology of the ocean.

This natural balance of temperature and humidity is being seriously destabilized by local deforestation and deliberate forest fires. Experts warn that one of the worst effects of deforestation is that the area’s water cycle may soon become irreversibly broken, locking in a trend of declining rainfall and longer dry seasons.

Scientists warn of a series of irreversible climate tipping points that could be reached when deforestation reaches between 20 and 25 percent (the current level is 17 percent). At that point, it is predicted, 50 percent of the shrinking forest will turn to savanna. 12 13 14

How Does Africa Boost Plant Growth In The Amazon Rainforest?

According to data from NASA’s CALIPSO satellite, every year the Amazon rainforest receives an average of 182 million tons of lake-sediment dust from the African Sahara, 1,600 miles (2,600 km) away across the Atlantic Ocean. 15 The dust is rich in phosphorus, an important nutrient for plants that boosts growth. The windblown dust is a handy replacement for an equivalent amount of phosphorus which is typically washed out of the soil every year by rain and floods. 16 9

The Amazon River

The Amazon River is the life force of Amazonia. From its source – the headwaters of the Mantaro River on the Cordillera Rumi Cruz in Peru – high up in the snow-capped Andes 17 , the Amazon River flows more than 4,000 miles across the continent until it empties into the Atlantic Ocean at Belem, Brazil. Its size is staggering: deep enough to accommodate ocean liners for over half its length, its mouth can be up to 300 miles wide, while even 1,000 miles inland it is still more than 6 miles wide. The river winds through the center of the Amazon jungle and is joined by 1,100 tributaries, making it the largest watershed and largest river system in the world occupying over 6 million square kilometers (2.3 million square miles).

Map of the Amazon River drainage basin
Map of the Amazon River drainage basin showing its encroachment into Guyana, Columbia, Ecuador, Peru, Bolivia and Brazil. Image: © Kmusser/CC BY-SA 3.0

Every rainy season (mid-December to mid-May), river levels rise more than 9 metres (30 feet), flooding the surrounding rainforest. During the average dry season, around 110,000 square kilometres (42,000 square miles) of land are under water, while in the wet season, the flooded area extends to about 350,000 square kilometres (140,000 square miles). 18

As the river winds its way through the waterlogged Amazon Basin, it picks up soil, fungi, leaves, seeds, dead animals, and other bits of organic litter, and propels it all into the South Atlantic. This enormous outflow of nutrients into the sea has a major effect on marine life, nourishing microscopic, surface-dwelling, marine plants known as phytoplankton, which in turn provide food for a diverse range population of fish.

How Many Species Live In The Amazon?

The Amazon rainforest contains the richest diversity of any tract of land on the planet. Studies have reported finding over 1,100 tree species in a quarter square kilometer (62 acres) of Ecuadorian rainforest. 19 Overall, the Amazon Basin hosts 2.5 million species of insect, some 40,000 species of plant, 2,200 types of fish, 1 in 5 of all bird species, 428 types of amphibians and 378 species of reptile. 20

Strawberry Poison Dart Frogs are found in Central and South America, chiefly in the Amazon Basin.
Poison dart frogs are found in Central and South America, chiefly in the Amazon rainforest, and feed on termites, ants, crickets, and fruit flies. They convert chemicals from their food into poisons which they release from the skin when threatened. Sadly, an estimated 28 percent of the species are endangered due to deforestation and loss of habitat. Photo: © Marshal Hedin/CC BY-SA 2.0

Interestingly, the most abundant animals in the Amazon are ants. If weighed altogether, their combined biomass would be heavier than any other group of animals in the rainforest. There are more than one thousand species and tens of millions of individual ants. The Pulitzer Prize-winning biologist Edward O. Wilson once found over 200 species of ants on a single tree in the rainforest!

What Medications Come From The Rainforest?

Ever since humans began making tools more than 2.5 million years ago, they have used plants to make medicine, and still do. According to an estimate by the World Health Organization, 80 percent of people in developing countries depend upon traditional medicines, mostly botanical drugs, for their primary health care needs. See also: 10 Reasons Why Plants are Important.

With its incredible diversity of species, the rainforest continues to be the perfect bio-medical laboratory. Here are just a tiny few of its successful applications: 21

• Liana Vine
The alkaloid d-tubocurarine, derived from the poisonous bark of a liana vine, is used to treat conditions like Parkinson’s disease, multiple sclerosis and other muscular disorders.

• Yams
Yams from Mexico and Guatemala provide diosgenin and cortisone, active ingredients in birth control pills.

• Willow Trees
The chemical blueprint for aspirin is derived from extracts of willow trees found in the rainforest.

• Cat’s Claw
Its roots are used to cure a series of common conditions from rheumatism and toothaches to cuts and bruises.

• Cinchona
The bark of the Cinchona tree was used to make the world’s first effective quinine drug for the treatment of malaria. It was first discovered by the Peruvian Quechua tribe.

• Curare
From its poisonous bark researchers isolated the alkaloid d-turbocuarine, now used in the treatment of multiple sclerosis, Parkinson’s disease and other muscular disorders.

• Lapacho
Lapachois used in modern medicine to treat cancer, alleviate pain from chemotherapy and fight infection.

• Magnolias
Native to tropical forests, the magnolia plant is cultivated for the chemical honokiola, a traditional ingredient in Chinese medicine, venerated for its anti-cancer properties as well as its benefits for heart disease and dementia.

• Matico
Matico leaves are boiled to make a tea to ease sore throats, coughs and other common ailments.

• Rosy Periwinkle
This Madagascan plant provides two important anti-cancer agents for use in the treatment of lymphocytic leukemia and Hodgkin’s Disease.

• Shapumvilla
The Shapumvilla plant has coagulant properties to stop bleeding.

• Tawari Tree
Its bark is used to treat cancerous cells, tumors and inflammation. 22

• Yew Tree
Native to forests in Europe, northwest Africa and southwest Asia, its bark is used in the manufacture of Paclitaxel, one of the world’s most widely used cancer drugs.

Many other compounds from rainforest plants are used in drugs to treat conditions like high blood pressure, glaucoma, tuberculosis, and other health problems. 23

Bioprospecting In The Amazon Basin

Bioprospecting describes a relatively new activity, involving the search for new products based on biological resources, for application in pharmaceuticals, pesticides. agriculture, bioremediation, and nanotechnology. 24

In 1983, there were no known instances of U.S. manufacturers organizing research programs to obtain new drugs from botanicals. Today, several branches of the U.S. government, including the National Cancer Institute, along with more than 100 pharmaceutical companies, including multinational corporations such as Johnson & Johnson, Roche, Pfizer, Bayer, Merck, Monsanto, GlaxoSmithKline and others, are engaged in plant-based projects in an attempt to find pharmaceuticals to treat infections, AIDS and cancer.

Who Lives In The Amazon Rainforest?

Archeological evidence from the Caverna da Pedra Pintada indicates that human inhabitants first settled in the Amazon region around 11,200 years ago. 25 Thereafter, human settlement was believed to have been fairly sparse. However, recent anthropological discoveries suggest that the region was in fact quite densely populated. In 1500, for instance, the region was home to around 5 million people, divided between heavily populated coastal settlements, such as that at Marajo, and the less populated interior.

Then came European colonization and, with it, the introduction of strange new diseases – to which the the local inhabitants had developed no immunity – which led to the decimation of indigenous population. By 1900, the number of inhabitants had fallen to 1 million, and by the early 1980s it was down to 200,000. 26

They reside in 526 territories – occupying some 190 million acres – roughly twice the size of California. Approximately 188 million acres lie inside the Brazilian Amazon, in the states of Acre, Amapa, Amazonas, Maranhao, Mato Grosso, Para, Rondonia, Roraima, and Tocantins. In addition, there are belied to be as many as 50 or more indigenous groups still living in the dense interior of the rainforest, who have never had contact with the outside world.

How Does The Amazon Rainforest Affect Global Warming?

Climate scientists are principally concerned about the release of the carbon contained within the rainforest, which could raise the Earth’s temperature and accelerate climate change. Amazonian forests are estimated to contain around 132.6 billion tons of carbon. 27 At least one climate model indicates that the Amazon rainforest could become totally transformed under conditions of significantly reduced rainfall and increased temperatures, resulting in a more or less complete loss of tree cover by 2100. 28

Deforestation remains the more immediate danger, however, especially in light of the recent spate of fires along with political ambivalence as to the need to safeguard the rainforest.

This is ironic, given the results of surveys showing that conservation provides a higher financial return than any activity associated with deforestation or forest degradation. For example, one land use study calculated that one hectare (2.5 acres) in the Amazon rainforest has a value of $6820 if left intact and sustainably harvested for rubber (latex), timber and fruit; $1000 if cleared for commercial timber but not sustainably harvested; or $148 if cleared for cattle grazing. 29

In 2019 the Brazil government dismantled some of the legal protection given to the Amazon rainforest. This action resulted in a significant loss of trees. 30

For more about trees and climate change, see: Tree-Planting: Is it the Easy Answer to Global Warming?


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