There have been conflicts and warfare in the Amazonas between the Jivaro tribe's surrounding tribes. The Shuar were one of the Jivaroan tribes that engaged in headhunting for sport and head shrinkage. [6] According to missionaries who visited the region near the borders of Brazil and Venezuela, the Yanomami tribes were rife with internal strife. The average male Yanomamo died in battle more than one-third of the time. [7]
It is estimated that diseases brought by immigrants, such as typhus and malaria, killed 40,000 native Amazonians during the rubber boom.
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Geography
Location
The Amazon basin is shared by nine nations, but Brazil's boundaries contain the majority of the rainforest, at 58.4%. The remaining eight nations are Guyana at 3.1%, Suriname at 2.5%, French Guiana at 1.4%, Bolivia at 7.7%, Colombia at 7.1%, Peru at 12.8%, and Ecuador at 1%. [9]
Natural
Amazonian region of Colombia
Amazon jungle aerial picture near Manaus
Most likely, the Eocene age is when the rainforest first developed (from 56 million years to 33.9 million years ago). It emerged when the Atlantic Ocean had broadened enough to give the Amazon basin a warm, humid climate, following a global drop in tropical temperatures. The rainforest has existed for at least 55 million years, and much of the area was free of savanna-type biomes at least until the present ice age when the climate was drier and savanna was more prevalent. [10] [11]
The loss of the dinosaurs and the subsequent wetter environment may have encouraged the tropical rainforest to expand throughout the continent after the Cretaceous-Paleogene extinction event. The rainforest reached 45° of the south between 66 and 34 Mya. Savanna regions have expanded into the tropics as a result of climate changes during the past 34 million years. For instance, the rainforest only covered a relatively small area during the Oligocene. At the last glacial maximum, it contracted to a formation that was mostly inland until expanding once more during the Middle Miocene. [12] However, the rainforest continued to flourish throughout these glacial times, enabling a wide variety of animals to survive and evolve. [13]
a view from above of the Amazon jungle
The Purus Arch is thought to have split the continent in half during the mid-Eocene, dividing the Amazon drainage basin. Across the Amazonas Basin, the water on the eastern side moved in the direction of the Atlantic while moving in the direction of the Pacific.
There is proof that the last 21,000 years, during the last glacial maximum (LGM) and subsequent deglaciation, have seen substantial changes in the vegetation of the Amazon rainforest. Analysis of sedimentary deposits from the Amazon Fan and paleolakes in the basin shows that rainfall was lower than it is now during the LGM, and this was very certainly due to a reduction in the amount of moist tropical vegetation present there. [16] At the moment, the Amazon receives about 9 feet of rain every year. The extent of this reduction, however, is up for debate. Some scientists argue that the rainforest was reduced to few, isolated refugia divided by open woodland and grassland;[17] while others contend that the rainforest remained substantially intact but stretched less to the north, south, and east than it does now. [18] Because data sampling is biased away from the center of the Amazon basin due to the practical difficulties of working in the rainforest, both theories are quite well supported by the data currently available.
Wind-borne Sahara Desert dust enters the Amazon
The Bodélé depression in Northern Chad's Sahara desert provides more than 56% of the dust that feeds the Amazon rainforest. Phosphorus, which is crucial for plant growth, is present in the dust. The comparable quantity of phosphorus washed away each year in Amazon soil by rain and flooding is replaced each year by Sahara dust. [19]
The amount of dust that is windblown from the Sahara to the Amazon has been measured by NASA's CALIPSO satellite: on average, 182 million tons of dust are windblown out of the Sahara each year, crossing 2,600 kilometers (1,600 miles) over the Atlantic Ocean (some dust falls into the Atlantic), and then falling at 35 degrees West longitude at the eastern coast of South America, where 27.7 million tons (15%) of dust fall over the Amazon basin (of which 22 million tons are made up of o [20]A laser range finder is used by CALIPSO to scan the Earth's atmosphere for the vertical distribution of dust and other particles. Regularly, CALIPSO monitors the Sahara-Amazon dust plume. CALIPSO has seen changes in the amount of dust transported, with the lowest amount of dust transported in 2011 being 86% less than the maximum amount in 2007.
The Sahel, a region of semi-arid land on the southern edge of the Sahara, is one potential cause of the fluctuation. In the Sahel, there is less dust when there is more rain. In the Sahel, more vegetation may grow as a result of the higher rainfall, reducing the amount of sand that is exposed to wind-blown sand. [21]
Due to biomass burning in Africa, Amazon phosphorus also appears as smoke.
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[23]
Human endeavor
About 32,000 indigenous people call themselves Yanomami, and they reside in the Amazon rainforest.
Human settlers initially arrived in the Amazon region at least 11,200 years ago, according to archaeological data from an excavation at Caverna da Pedra Pintada.
[25] By AD 1250, further, development had brought late-prehistoric communities to the forest's edge, which changed the forest's cover. [26]
It was long believed that the Amazon rainforest was never more than thinly populated since the poor soil made it impossible to feed a big population through agriculture. This theory was widely supported by archaeologist Betty Meggers, according to her book Amazonia: Man and Culture in a Counterfeit Paradise. According to her, hunting can only support a maximum population density of 0.2 people per square kilometer (0.52/sq mi) in the jungle; to support a greater population, agriculture is required. [27]Recent anthropological research, however, indicates that the area was actually heavily populated. In the Amazon basin in AD 1500, there may have been 5 million people living in dense coastal villages like Marajó and inland communities. [28] The population was less than 200,000 in the early 1980s compared to less than 1 million in 1900. [28]
In 1542, Francisco de Orellana became the first European to travel the whole length of the Amazon River. [29] The BBC's Unnatural Histories offers proof that Orellana was accurate in his findings that a sophisticated civilization was flourishing along the Amazon in the 1540s, as opposed to exaggerating his assertions as was previously believed. It is said that illnesses imported from Europe, including smallpox, later wreaked havoc on society. [30] Early in the 20th century, British adventurer Percy Fawcett studied this civilization. His missions yielded conflicting results, and on his final journey, he inexplicably vanished. He called this vanished culture the City of Z.
Numerous geoglyphs dating from AD 1 to 1250 have been found on deforested terrain since the 1970s, supporting theories concerning pre-Columbian civilizations. [31] [32] Alceu Ranzi is credited with promoting the geoglyphs' discovery after flying above Acre, though Ondemar Dias is credited with discovering them first in 1977. [30] [33] The BBC's Unnatural Histories showed proof that, rather than being a pure wilderness, the Amazon rainforest has been changed by man for at least 11,000 years through techniques like terra preta and forest gardening. [30] Large swaths of the Amazon rainforest are covered in terra preta, which is now generally recognized as the result of indigenous soil management. Large areas of the Amazon rainforest are likely the product of millennia of human control, rather than naturally occurring as has traditionally been assumed, because the creation of this fertile soil allowed agriculture and silviculture in the formerly inhospitable environment. [34] Remains of several of these sizable towns in the heart of the Amazon forest were discovered in the Xingu tribe's area in 2003 by Michael Heckenberger and colleagues from the University of Florida. These included signs of highways, overpasses, and sizable plazas. [35]
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