The Amazon: The World's Largest Rainforest
By Rhett Butler
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.
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.
The World's Largest Rainforests [more]
1. Amazon Basin, South America
2. Congo Basin, Africa
3. Indonesian Archipelago, Southeast Asia
How large is the Amazon rainforest?
The extent of the Amazon depends on the definition. The the Amazon River drains about 6.915 million sq km (2.722 sq mi), or roughly 40 percent of South America, but generally areas outside the basin are included when people speak about "the Amazon." The biogeographic Amazon ranges from 7.76-8.24 million sq km (3-3.2 million sq km), of which just over 80 percent is forested. For comparison, the land area of the United States (including Alaska and Hawaii) is 9,629,091 square kilometers (3,717,811).
Nearly two-thirds of the Amazon lies in Brazil.
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
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.
THE AMAZON RAINFOREST
While the Amazon Basin is home to the world's largest tropical rainforest, the region consists of a number of 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 rainforest ecology section.
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., 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 is slowing, mostly due to to the sharp drop in forest clearing in Brazil since 2004.
Brazil's declining deforestation rate has been attributed to several factors, some of which it controls, some of which it doesn't. Since 2000 Brazil has established the world's largest network of protected areas, the majority of which are located in the Amazon region. Since 2004 the government has also had a deforestation reduction program in place. This includes improved law enforcement, satellite monitoring, and financial incentives for respecting environmental laws. Furthermore, the private sector — especially the soy, logging, and cattle industries — are increasingly responsive to consumer demand for less-damaging commodities. Finally the Brazilian Amazon has been the site of a number of innovative and ambitious conservation experiments, ranging from jurisdictional commodity certification to indigenous led Reducing Emissions from Deforestation and Degradation (REDD+) projects to Norway's billion dollar performance-based payment for cutting deforestation.
RECENT NEWS ON THE AMAZON
Tropical deforestation could disrupt rainfall globally
Large-scale deforestation in the tropics could drive significant and widespread shifts in rainfall distribution and temperatures, potentially affecting agriculture both locally and far from where forest loss is occurring, concludes a study published today in Nature Climate Change.
Amazonian peatlands store mega carbon
Peatlands in the Peruvian Amazon store ten times the amount of carbon as undisturbed rainforest in adjacent areas, making them critical in the battle to fight climate change, finds a new study published in Environmental Research Letters.
Indigenous communities 'among the very few best protectors' of Peruvian Amazon
A new report examines the effects of timber harvesting, gold mining, agriculture, and oil and natural gas drilling that have been on the rise recently in the Peruvian Amazon, and states that ensuring indigenous land rights is a key tool in the fight to protect it.
False victories for sustainability – Amazonian Hydropower
Dams are hugely controversial, especially in the Amazon Rainforest. Their proponents, flashing green credentials, have dammed the tributaries of the Amazon for decades. However, there is a rising backlash against the huge economical, environmental, and sociological costs dams bring. A paper led by Dr. James Randall Kahn from Washington and Lee University is the latest in this volley.
Indigenous leader murdered before he could attend Climate Summit
Days before José Isidro Tendetza Antún was supposed to travel to the UN Climate Summit in Lima to publicly file a complaint against a massive mining operation, he went missing. Now, the Guardian reports that the body of the Shuar indigenous leader has been found, bound and buried in an unmarked grave on the banks of the Zamora River.
How an indigenous community in Ecuador stood up to big oil - and won
The Sarayaku, a Kichwa indigenous people numbering 1,200 from the Ecuadorian Amazon, won a historic court case in 2012. The Inter-American Court of Human Rights ruled that the government of Ecuador must publicly apologize, consult with, and recompense the Sarayaku for allowing oil exploration by Argentine Compañia General de Combustibles on their territory without prior consultation
Giant stone face unveiled in the Amazon rainforest (video)
A new short film documents the journey of an indigenous tribe hiking deep into their territory in the Peruvian Amazon to encounter a mysterious stone countenance that was allegedly carved by ancient peoples. According to Handcrafted Films, which produced the documentary entitled The Reunion, this was the first time the Rostro Harakbut has been filmed.
Deforestation jumps in Peru
Deforestation in the Peruvian Amazon increased significantly last year, says a top official.
Threatened indigenous forests store more than half the Amazon's carbon
A new study released today finds the total carbon load locked up in parts of the Amazon rainforest held by indigenous groups to be much higher than previously estimated – an amount that, if released, would be capable of destabilizing the earth’s atmosphere. But because of flimsy land rights, these areas stand at risk of deforestation.
Amazon deforestation in Brazil drops 18% in 2013/2014
Figures published Wednesday by Brazil's National Space Research Institute (INPE) show that 4,848 square kilometers (1,871 square miles) of forest — an area about the size of the state of Rhode Island or the country of Brunei — were cleared between August 2013 and July 2014.
What we can learn from uncontacted rainforest tribes
If you have ever wondered about the connection between hallucinogenic frogs, uncontacted peoples, conservation, and climate change — and who hasn't? — check out this TED talk from ethnobotanist Mark Plotkin. An ethnobotanist by training, Plotkin serves as President of the Amazon Conservation Team. Plotkin took a few minutes from his busy schedule to answer a few questions from Mongabay.
Amazon deforestation moratorium extended 18 months
The Brazilian soy industry has extended its deforestation moratorium for another 18 months. The moratorium, which was established in 2006 after a high-profile Greenpeace campaign, bars conversion of forests in Brazilian Amazon for soy production. Independent analysis has shown it to be highly effective — just prior to the moratorium, soy accounted for roughly a fifth of recent deforestation, while today its share is less than one percent.
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AMAZON RAINFOREST PICTURE HIGHLIGHTS
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