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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.
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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
Amazon rainforest will bear cost of biofuel policies in Brazil
(02/08/2010)
Business-as-usual agricultural expansion to meet biofuel production targets for 2020 will take a heavy toll on Brazil's Amazon rainforest in coming years, undermining the potential emissions savings of transitioning from fossil fuels to biofuels, warns a new paper published in the Proceedings of the National Academy of Sciences (PNAS). The research suggests that intensification of cattle ranching, combined with efforts to promote high-yielding oil crops like oil palm could lessen forecast greenhouse gas emissions from indirect land use in the region.
Commodity trade and urbanization, rather than rural poverty, drive deforestation
(02/07/2010)
Deforestation is increasingly correlated to urban population growth and trade rather than rural poverty, suggesting that measures proposed to reduce deforestation will be ineffective if they fail to address demand for commodities produced on forest lands, argues a new paper published in Nature GeoScience.
Birder captures first footage ever of long whiskered owlet, one of the world's rarest birds
(02/04/2010)
It was any birders dream come true: not only to see one of the world's rarest birds, but to discover a new unknown population. Israeli birder, Shachar Alterman, was surveying birds with the UK organization Neotropical Primate Conservation in Peruvian cloud forest when he heard and then saw the long whiskered owlet.
The Amazongate fiasco
(02/03/2010)
A claim published in the Sunday Times over the veracity of a statement published in an Intergovernmental Panel on Climate Change (IPCC) report may land the British newspaper in hot water. On Sunday, Jonathan Leake, Science & Environment Editor of the Sunday Times, accused the IPCC of making a "bogus rainforest claim" when it cited a report warning that up to 40 percent of the Amazon could be "drastically" affected by climate change. Climate change skeptics immediately seized on "Amazongate" as further evidence to discredit the IPCC just two weeks after it was found to be using shoddy glacier data in its 2007 climate assessment.
Rainforest expert agrees with IPCC: warns of 'tipping point' for Amazon
(02/03/2010)
Amid questions over the Amazon forests' capacity to survive climate change, a renowned tropical biologist says that in fact the fears are real, reports Tierramerica. Speaking at the Biodiversity Science Policy Conference in Paris, Thomas Lovejoy, biodiversity chair at the Washington DC-based Heinz Center for Science, Economics and the Environment, and chief biodiversity adviser to the president of the World Bank, described the Amazon rainforest as "very close to a tipping point".
Environmentalists and indigenous groups decry approval of massive dam in Amazon
(02/02/2010)
The approval of the hydro-electric Belo Monte Dam from the Brazilian environmental agency, IBAMA, has raised condemnations from environmentalists and indigenous groups. The dam will divert the flow of the Xingu River, a tributary of the Amazon River, which runs through the Amazon in northeast Brazil. According to critics the dam will destroy vast areas of pristine rainforest, disrupt sensitive ecosystems, and relocate 12,000 people.
Farmers drive deforestation in Rondonia, in the Brazilian Amazon
(01/31/2010)
Small-scale farmers who lease land from the Brazilian government are very much responsible for deforestation in the Brazilian state of Rondonia in the Amazon area. In most areas with agrarian projects, more than fifty percent of the land has been cleared of forests, while the Brazilian Forestry Code permits farming concerns in the Amazon to clear only twenty percent of the land.
Photos: park in Ecuador likely contains world’s highest biodiversity, but threatened by oil
(01/19/2010)
In the midst of a seesaw political battle to save Yasuni National Park from oil developers, scientists have announced that this park in Ecuador houses more species than anywhere else in South America—and maybe the world. "Yasuní is at the center of a small zone where South America's amphibians, birds, mammals, and vascular plants all reach maximum diversity," Dr. Clinton Jenkins of the University of Maryland said in a press release. "We dubbed this area the 'quadruple richness center.'"
Uncontacted natives confirmed in Brazil
(01/10/2010)
An uncontacted tribe of about 60 people has been confirmed by FUNAI (Brazil's Indigenous Affairs Department) in the Indigenous Territory of Arariboia, located in the eastern Amazonian state, Maranhao.
Gone: a look at extinction over the past decade
(01/03/2010)
No one can say with any certainty how many species went extinct from 2000-2009. Because no one knows if the world's species number 3 million or 30 million, it is impossible to guess how many known species—let alone unknown—may have vanished recently. Species in tropical forests and the world's oceans are notoriously under-surveyed leaving gaping holes where species can vanish taking all of their secrets—even knowledge of their existence—with them.
Rainforest conservation: a year in review
(12/27/2009)
2009 may prove to be an important turning point for tropical forests. Lead by Brazil, which had the lowest extent of deforestation since at least the 1980s, global forest loss likely declined to its lowest level in more than a decade. Critical to the fall in deforestation was the global financial crisis, which dried up credit for forest-destroying activities and contributed to a crash in commodity prices, an underlying driver of deforestation.
Ecuador to be paid to leave oil in the ground
(12/23/2009)
Ecuador will establish a trust fund for receiving payments to leave oil reserves unexploited in Yasuni National Park, one of the world's most biodiverse rainforest reserves, reports the UN Development Programme, the agency that will administer the fund.
Brazil establishes 20,000 sq mi of new indigenous reserves in the Amazon
(12/23/2009)
On Monday, Brazil decreed nine new indigenous reserves covering 51,000 square kilometers (19,700 square miles) of the Amazon rainforest, an areas larger than Denmark or Switzerland, reports the AFP. Five of the reserves are located in the state of Amazonas, two are in Pará, one is in Roraima, and another is in Mato Grosso do Sul. The protected areas house about seven thousand Indians from 29 ethnic groups, according to FUNAI (Fundação Nacional do Índio), Brazil's indigenous affairs agency.
The real Avatar story: indigenous people fight to save their forest homes from corporate exploitation
(12/22/2009)
In James Cameron's newest film Avatar an alien tribe on a distant planet fights to save their forest home from human invaders bent on mining the planet. The mining company has brought in ex-marines for 'security' and will stop at nothing, not even genocide, to secure profits for its shareholders. While Cameron's film takes place on a planet sporting six-legged rhinos and massive flying lizards, the struggle between corporations and indigenous people is hardly science fiction.
Brazil grants deforestation amnesty for farmers and ranchers
(12/14/2009)
A decree issued by President Luiz Inacio Lula da Silva suspends up to $5.7 billion in fines and gives ranchers and farmers in the Amazon two more years to come into compliance with environmental laws aimed to curtain deforestation, reports the Associated Press.
Ecuador’s Rafael Correa: Copenhagen Climate Hero or Environmental Foe?
(12/14/2009)
As climate change negotiations continue full force in the Danish city of Copenhagen, Latin American countries are hoping the Global North will commit to its “climate debt” by reducing greenhouse gas emissions and providing resources to poor nations. It’s certainly an understandable aspiration: Latin America only produces five per cent of global emissions of carbon dioxide, a chief greenhouse gas, yet the region has borne the brunt of extreme weather ranging from droughts to flooding.
Amazon cattle ranching accounts for half of Brazil's CO2 emissions
(12/12/2009)
Cattle ranching accounts for half of Brazil's greenhouse gas emissions according to a new study led by scientists from Brazil's National Space Institute for Space Research (INPE).
Google Earth to monitor deforestation
(12/10/2009)
It what could be a critical development in helping tropical countries monitor deforestation, Google has unveiled a partnership with scientists using advanced remote sensing technology to rapidly analyze and map forest cover in extremely high resolution. The effort could help countries detect deforestation shortly after it occurs making it easier to prevent further forest clearing.
Brazil allocates first funds under plan to save the Amazon
(12/10/2009)
Brazil's development bank BNDES has announced the first five recipients of grants under the South American country's ambitious Amazon Fund, which aims to reduce deforestation by 70 percent over the next decade.
Changing drivers of deforestation provide new opportunities for conservation
(12/09/2009)
Tropical deforestation claimed roughly 13 million hectares of forest per year during the first half of this decade, about the same rate of loss as the 1990s. But while the overall numbers have remained relatively constant, they mask a transition of great significance: a shift from poverty-driven to industry-driven deforestation and geographic consolidation of where deforestation occurs. These changes have important implications for efforts to protect the world's remaining tropical forests in that environmental lobby groups now have identifiable targets that may be more responsive to pressure on environmental concerns than tens of millions of impoverished rural farmers. In other words, activists have more leverage than ever to impact corporate behavior as it relates to deforestation.
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