Amazon
The Amazon rainforest (Brazilian Portuguese: Floresta Amazônica or Amazônia; Spanish: Selva Amazónica or Amazonia), also known as Amazonia, or the Amazon jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America. This basin encompasses seven million square kilometers (1.7 billion acres), of which five and a half million square kilometers (1.4 billion acres) are covered by the rainforest. This region includes territory belonging to nine nations. The majority of the forest is contained within Brazil, with 60% of the rainforest, followed by Peru with 13%, and with minor amounts in Colombia, Venezuela, Ecuador, Bolivia, Guyana, Suriname, and French Guiana. States or departments in four nations bear the name Amazonas after it. The Amazon represents over half of the planet's remaining rainforests, and it comprises the largest and most species-rich tract of tropical rainforest in the world.
The Amazon rainforest was short-listed in 2008 as a candidate to one of the New7Wonders of Nature by the New Seven Wonders of the World Foundation. As of February 2009 the Amazon was ranking first in Group E, the category for forests, national parks and nature reserves.[1]
The Amazon rainforest (Brazilian Portuguese: Floresta Amazônica or Amazônia; Spanish: Selva Amazónica or Amazonia), also known as Amazonia, or the Amazon jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America. This basin encompasses seven million square kilometers (1.7 billion acres), of which five and a half million square kilometers (1.4 billion acres) are covered by the rainforest. This region includes territory belonging to nine nations. The majority of the forest is contained within Brazil, with 60% of the rainforest, followed by Peru with 13%, and with minor amounts in Colombia, Venezuela, Ecuador, Bolivia, Guyana, Suriname, and French Guiana. States or departments in four nations bear the name Amazonas after it. The Amazon represents over half of the planet's remaining rainforests, and it comprises the largest and most species-rich tract of tropical rainforest in the world.
The Amazon rainforest was short-listed in 2008 as a candidate to one of the New7Wonders of Nature by the New Seven Wonders of the World Foundation. As of February 2009 the Amazon was ranking first in Group E, the category for forests, national parks and nature reserves.[1]
Etymology
The name Amazon is said to arise from a war which Francisco de Orellana had with a tribe of Tapuyas and other tribes from South America. The women of the tribe fought alongside the men, as was the custom among the entire tribe.[2] Orellana's descriptions may have been accurate, but a few historians speculate that Orellana could have been mistaking indigenous men wearing "grass skirts" for women.[citation needed] Orellana derived the name Amazonas from the ancient Amazons of Asia and Africa described by Herodotus and Diodorus in Greek legends.[2]
Another etymology for the word suggests that it came originally from a native word amazona (Spanish spelling) or amassona (Portuguese spelling), meaning "destroyer (of) boats", in reference to the destructive nature of the root system possessed by some riparian plants.
Another etymology for the word suggests that it came originally from a native word amazona (Spanish spelling) or amassona (Portuguese spelling), meaning "destroyer (of) boats", in reference to the destructive nature of the root system possessed by some riparian plants.
History
The rainforest likely formed during the Eocene era, following the evolutionary appearance of angiosperm plants. It appeared following a global reduction of tropical temperatures when the Atlantic Ocean had widened sufficiently to provide a warm, moist climate to the Amazon basin. The rain forest has been in existence for at least 55 million years, and most of the region remained free of savanna-type biomes during that time period.[3][4]
Following the Cretaceous–Tertiary extinction event, the extinction of the dinosaurs and the wetter climate may have allowed the tropical rainforest to spread out across the continent. From 65–34 Mya, the rainforest extended as far south as 45°. Climate fluctuations during the last 34 million years have allowed savanna regions to expand into the tropics. During the Oligocene, for example, the rainforest spanned a relatively narrow band that lay mostly above latitude 15°N. It expanded again during the Middle Miocene, then retracted to a mostly inland formation at the last glacial maximum.[5] However, the rainforest still managed to thrive during these glacial periods, allowing for the survival and evolution of a broad diversity of species.[6]
During the mid-Eocene, it is believed that the drainage basin of the Amazon was split along the middle of the continent by the Purus Arch. Water on the eastern side flowed toward the Atlantic, while to the west water flowed toward the Pacific across the Amazonas Basin. As the Andes Mountains rose, however, a large basin was created that enclosed a lake; now known as the Solimões Basin. Within the last 5–10 million years, this accumulating water broke through the Purus Arch, joining the easterly flow toward the Atlantic.[7][8]
There is evidence that there have been significant changes in Amazon rainforest vegetation over the last 21,000 years through the Last Glacial Maximum (LGM) and subsequent deglaciation. Analyses of sediment deposits from Amazon basin paleolakes and from the Amazon Fan indicate that rainfall in the basin during the LGM was lower than for the present, and this was almost certainly associated with reduced moist tropical vegetation cover in the basin.[9] There is debate, however, over how extensive this reduction was. Some scientists argue that the rainforest was reduced to small, isolated refugia separated by open forest and grassland;[10] other scientists argue that the rainforest remained largely intact but extended less far to the north, south, and east than is seen today.[11] This debate has proved difficult to resolve because the practical limitations of working in the rainforest mean that data sampling is biased away from the center of the Amazon basin, and both explanations are reasonably well supported by the available data.
Based on archaeological evidence from an excavation at Caverna da Pedra Pintada, human inhabitants first settled in the Amazon region at least 11,200 years ago.[12] Subsequent development led to late-prehistoric settlements along the periphery of the forest by 1250 CE, which induced alterations in the forest cover.[13] Biologists believe that a population density of 0.2 persons/km2 is the maximum that can be sustained in the rain forest through hunting. Hence, agriculture is needed to host a larger population.[14] The first European to travel the length of the Amazon River was Francisco de Orellana in 1542.
Following the Cretaceous–Tertiary extinction event, the extinction of the dinosaurs and the wetter climate may have allowed the tropical rainforest to spread out across the continent. From 65–34 Mya, the rainforest extended as far south as 45°. Climate fluctuations during the last 34 million years have allowed savanna regions to expand into the tropics. During the Oligocene, for example, the rainforest spanned a relatively narrow band that lay mostly above latitude 15°N. It expanded again during the Middle Miocene, then retracted to a mostly inland formation at the last glacial maximum.[5] However, the rainforest still managed to thrive during these glacial periods, allowing for the survival and evolution of a broad diversity of species.[6]
During the mid-Eocene, it is believed that the drainage basin of the Amazon was split along the middle of the continent by the Purus Arch. Water on the eastern side flowed toward the Atlantic, while to the west water flowed toward the Pacific across the Amazonas Basin. As the Andes Mountains rose, however, a large basin was created that enclosed a lake; now known as the Solimões Basin. Within the last 5–10 million years, this accumulating water broke through the Purus Arch, joining the easterly flow toward the Atlantic.[7][8]
There is evidence that there have been significant changes in Amazon rainforest vegetation over the last 21,000 years through the Last Glacial Maximum (LGM) and subsequent deglaciation. Analyses of sediment deposits from Amazon basin paleolakes and from the Amazon Fan indicate that rainfall in the basin during the LGM was lower than for the present, and this was almost certainly associated with reduced moist tropical vegetation cover in the basin.[9] There is debate, however, over how extensive this reduction was. Some scientists argue that the rainforest was reduced to small, isolated refugia separated by open forest and grassland;[10] other scientists argue that the rainforest remained largely intact but extended less far to the north, south, and east than is seen today.[11] This debate has proved difficult to resolve because the practical limitations of working in the rainforest mean that data sampling is biased away from the center of the Amazon basin, and both explanations are reasonably well supported by the available data.
Based on archaeological evidence from an excavation at Caverna da Pedra Pintada, human inhabitants first settled in the Amazon region at least 11,200 years ago.[12] Subsequent development led to late-prehistoric settlements along the periphery of the forest by 1250 CE, which induced alterations in the forest cover.[13] Biologists believe that a population density of 0.2 persons/km2 is the maximum that can be sustained in the rain forest through hunting. Hence, agriculture is needed to host a larger population.[14] The first European to travel the length of the Amazon River was Francisco de Orellana in 1542.
Deforestation
Main article: Deforestation of the Amazon Rainforest
Deforestation is the conversion of forested areas to non-forested areas. The main sources of deforestation in the Amazon are human settlement and development of the land.[26] Prior to the early 1960s, access to the forest's interior was highly restricted, and the forest remained basically intact. Farms established during the 1960s was based on crop cultivation and the slash and burn method. However, the colonists were unable to manage their fields and the crops because of the loss of soil fertility and weed invasion.[28] The soils in the Amazon are productive for just a short period of time, so farmers are constantly moving to new areas and clearing more land.[28] These farming practices led to deforestation and caused extensive environmental damage.[29]
Between 1991 and 2000, the total area of forest lost in the Amazon rose from 415,000 to 587,000 km2, with most of the lost forest becoming pasture for cattle.[30] Seventy percent of formerly forested land in the Amazon, and 91% of land deforested since 1970, is used for livestock pasture.[31][32] In addition, Brazil is currently the second-largest global producer of soybeans after the United States. The needs of soy farmers have been used to validate many of the controversial transportation projects that are currently developing in the Amazon. The first two highways successfully opened up the rain forest and led to increased settlement and deforestation. The mean annual deforestation rate from 2000 to 2005 (22,392 km2 per year) was 18% higher than in the previous five years (19,018 km2 per year).[33] At the current rate, in two decades the Amazon Rainforest will be reduced by 40%.[34]
Main article: Deforestation of the Amazon Rainforest
Deforestation is the conversion of forested areas to non-forested areas. The main sources of deforestation in the Amazon are human settlement and development of the land.[26] Prior to the early 1960s, access to the forest's interior was highly restricted, and the forest remained basically intact. Farms established during the 1960s was based on crop cultivation and the slash and burn method. However, the colonists were unable to manage their fields and the crops because of the loss of soil fertility and weed invasion.[28] The soils in the Amazon are productive for just a short period of time, so farmers are constantly moving to new areas and clearing more land.[28] These farming practices led to deforestation and caused extensive environmental damage.[29]
Between 1991 and 2000, the total area of forest lost in the Amazon rose from 415,000 to 587,000 km2, with most of the lost forest becoming pasture for cattle.[30] Seventy percent of formerly forested land in the Amazon, and 91% of land deforested since 1970, is used for livestock pasture.[31][32] In addition, Brazil is currently the second-largest global producer of soybeans after the United States. The needs of soy farmers have been used to validate many of the controversial transportation projects that are currently developing in the Amazon. The first two highways successfully opened up the rain forest and led to increased settlement and deforestation. The mean annual deforestation rate from 2000 to 2005 (22,392 km2 per year) was 18% higher than in the previous five years (19,018 km2 per year).[33] At the current rate, in two decades the Amazon Rainforest will be reduced by 40%.[34]
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