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The Amazon: The World's Largest Rainforest
By Rhett A. Butler [citation]
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% 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 (formerly the Zaire) river. The river system is the lifeline of the forest and its history plays an important part in the development of its rainforests.
HISTORY
At one time Amazon River flowed westward, perhaps as part of a proto-Congo (Zaire) 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 chapter 3-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.
THE AMAZON RIVER TODAY
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How large is the Amazon rainforest?
In Brazil, the Amazon covers surface area of 4,100,000 square kilometers (1,583,000 square miles), of which around 3.4 million sq km (1.3 million sq mi) are presently forested. Accounting for parts of the Amazon outside of Brazil, the total extent of the Amazon is estimated at 8,235,430 sq km (3,179,715 sq mi). or comparison, the land area of the United States (including Alaska and Hawaii) is 9,629,091 square kilometers (3,717,811).
In total, the Amazon River drains about 6,915,000 square kilometers (2,722,000 square miles), or roughly 40 percent of South America.
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Today the Amazon River is the most voluminous river on Earth, eleven times the volume of the Mississippi, and drains an area equivalent in size to the United States. During the high water season, the river's mouth may be 300 miles wide and every day up to 500 billion cubic feet of water (5,787,037 cubic feet/sec) flow into the Atlantic. For reference, the Amazon's daily freshwater discharge into the Atlantic is enough to 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.
(NEXT Amazon rainforest ecology)
Recent news on the Amazon
Value of timber stocks could predict future logging roads, deforestation in the Amazon
(05/20/2012)
A new model aims to forecast future logging road development by estimating the value of timber stocks across the Brazilian Amazon. The research, published in PLoS One, could help prioritize areas for conservation to protect the maximum area of forest.
Brazilian deforestation lower in 2012 to date
(05/18/2012)
Deforestation in the Brazilian Amazon is lower in 2012 relative to the same period last year according to satellite-based data released by Imazon, an NGO.
U.S. car manufacturers linked to Amazon destruction, slave labor
(05/14/2012)
According to a new report by Greenpeace, top U.S. car companies such as Ford, General Motors, and Nissan are sourcing pig iron that has resulted in the destruction of Amazon rainforests, slave labor, and land conflict with indigenous tribes. Spending two years documenting the pig iron trade between northeastern Brazil and the U.S., Greenpeace has discovered that rainforests are cut and burned to power blast furnaces that produce pig iron, which is then shipped to the U.S. for steel production.
Greenpeace makes social media push for zero deforestation in Brazil
(05/12/2012)
Greenpeace is leveraging social media in its push for a zero deforestation target in Brazil.
Can loggers be conservationists?
(05/10/2012)
Last year researchers took the first ever publicly-released video of an African golden cat (Profelis aurata) in a Gabon rainforest. This beautiful, but elusive, feline was filmed sitting docilely for the camera and chasing a bat. The least-known of Africa's wild cat species, the African golden cat has been difficult to study because it makes its home deep in the Congo rainforest. However, researchers didn't capture the cat on video in an untrammeled, pristine forest, but in a well-managed logging concession by Precious Woods Inc., where scientist's cameras also photographed gorillas, elephants, leopards, and duikers.
Pictures of Yasuni, Ecuador's rainforest gem
(04/27/2012)
In late 2010, mongabay.com reporter Jeremy Hance traveled to Yasuni National Park, arguably the most biodiverse place on the planet and home to a unique initiative to save a rainforest by asking the international community to pay to keep oil in the ground. Researchers have found more tree species in a single hectare in Yasuni National Park than in all of the U.S. and Canada combined. Yasuni also contains the highest biodiversity of reptiles and amphibians in the world with 271 species. But insects trump them all: entomologist Terry Erwin has estimated that a single hectare of rainforest in Yasuni may contain as many as 100,000 unique insect species.
Brazil's Congress OKs weakened version of forest law; environmentalists outraged
(04/26/2012)
Brazil's Congress on Wednesday approved controversial changes to the country's Forest Code, a move supporters argue will simplify environmental laws and ease agricultural expansion, but environmentalists say will spark deforestation and grant amnesty for past illegal logging. The measure needs to be approved by President Dilma Rousseff to become law.
Oil company Perenco endangering 'uncontacted' indigenous people, says Peru
(04/25/2012)
The company hoping to exploit the oil deposits slated to transform Peru’s economy has been declared to be endangering the lives of indigenous people living in "voluntary isolation" by the country’s indigenous affairs department (INDEPA). Perenco, an Anglo-French company with headquarters in London and Paris, is currently seeking approval from Peru’s Energy Ministry (MEM) to develop its operations in the Loreto region in the north of the country.
Featured video: How to save the Amazon
(04/22/2012)
The past ten years have seen unprecedented progress in fighting deforestation in the Amazon. Indigenous rights, payments for ecosystem services, government enforcement, satellite imagery, and a spirit of cooperation amongst old foes has resulted in a decline of 80 percent in Brazil's deforestation rates.
Protesters hit Brazilian mining giant Vale over involvement in Belo Monte
(04/20/2012)
More than 150 demonstrators protested outside Vale's headquarters in Rio de Janeiro during the Brazilian mining giant's annual shareholder meeting over the company's social and environmental record, reports Amazon Watch, a group that is fighting the massive Belo Monte dam.
Photos: Uncontacted Amazon tribes documented for first time in Colombia
(04/19/2012)
Aerial surveys of a remote area of rainforest along the Colombia-Brazil border have produced the first photographic evidence of uncontacted tribes, according to a conservation group that works to safeguard indigenous territories and culture. The photos, released by the Amazon Conservation Team (ACT), show five long houses or malokas thought to belong to two indigenous groups, the Yuri or Carabayo and Passé, some of the last isolated tribes in the Colombian Amazon. The images provide confirmation that uncontacted communities still exist within the Rio Puré National Park, which protects a million hectares (2.47 million acres) of mostly pristine rainforest between the Caquetá and Putumayo River basins along the Brazilian border.
Indigenous groups oppose priest pushing for road through uncontacted tribes' land
(04/19/2012)
A grassroots indigenous organization in Peru is calling for the removal of an Italian Catholic priest from the remote Amazon in response to his lobbying to build a highway through the country’s biggest national park.
Will mega-dams destroy the Amazon?
(04/18/2012)
More than 150 new dams planned across the Amazon basin could significantly disrupt the ecological connectivity of the Amazon River to the Andes with substantial impacts for fish populations, nutrient cycling, and the health of Earth's largest rainforest, warns a comprehensive study published in the journal PLoS ONE. Scouring public data and submitting information requests to governments, researchers Matt Finer of Save America’s Forests and Clinton Jenkins of North Carolina State University documented plans for new dams in Bolivia, Brazil, Colombia, Ecuador, and Peru.
Pictures: Destruction of the Amazon's Xingu River begins for Belo Monte Dam
(04/18/2012)
The Xingu River will never be the same. Construction of Belo Monte Dam has begun in the Brazilian Amazon, as shown by these photos taken by Greenpeace, some of the first images of the hugely controversial project. Indigenous groups have opposed the dam vigorously for decades, fearing that it will upend their way of life. Environmentalists warn that the impacts of the dam—deforestation, methane emissions, and an irreparable changes to the Xingu River's ecosystem—far outweigh any benefits. The dam, which would be the world's third largest, is expected to displace 16,000 people according to the government, though some NGOs put the number at 40,000. The dam will flood over 40,000 hectares of pristine rainforest, an area nearly seven times the size of Manhattan.
Amazon tribe becomes first to get OK to sell REDD credits for rainforest conservation
(04/12/2012)
An Amazon tribe has become the first indigenous group in the world's largest rainforest to win certification of a forest carbon conservation project, potentially setting a precedent for other forest-dependent groups to seek compensation for safeguarding their native forests.
Scientists unlock indigenous secret to sustainable agriculture in the Amazon's savannas
(04/11/2012)
Indigenous populations in the Amazon successfully farmed without the use of fire before the arrival of Europeans, demonstrating a potentially sustainable approach to land management in a region that is increasingly vulnerable to man-made fires.
U.S. gobbling illegal wood from Peru's Amazon rainforest
(04/10/2012)
The next time you buy wood, you may want to make sure it's not from Peru. According to an in-depth new report by the Environmental Investigation Agency (EIA), the illegal logging trade is booming in the Peruvian Amazon and much of the wood is being exported to the U.S. Following the labyrinthian trail of illegal logging from the devastated forests of the Peruvian Amazon to the warehouses of the U.S., the EIA identified over 112 shipments of illegally logged cedar and big-leaf mahogany between January 2008 and May 2010. In fact, the group found that over a third (35 percent) of all the shipments of cedar and mahogany from Peru to the U.S. were from illegal sources, a percentage that is likely conservative.
Brazil can eliminate deforestation by 2020, says governor of giant Amazon state
(04/05/2012)
Brazil can reduce Amazon deforestation to zero by 2020 while boosting rural livelihoods and maintaining healthy economic growth, the governor of Pará told mongabay.com on the sidelines of the Skoll World Forum, a major conference on social entrepreneurship, last week. Governor Simao Jatene is hopeful that a revolution in land management and governance can turn the tide in Pará, a state that is three times the size of California and has lost more Amazon forest -- 90,000 sq km of Amazon forest since 1996 -- over the past decade-and-a-half than any other in Brazil.
BP moves into the Amazon rainforest
(04/03/2012)
BP has acquired a stake in on exploration block in the heart of the Amazon rainforest, reports MarketWatch.
Judge suspends Brazilian dam that would flood sacred waterfalls
(04/02/2012)
A federal judge has suspended the construction of a 1,820 megawatt dam on the Teles Pires River in the Amazon. The judge found that indigenous communities were not properly consulted about the dam, which would flood a sacred site, known as the Seven Waterfalls, as well as imperil the livelihoods of indigenous fishermen.
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