![]() Delta core samples suggest that even the mighty Congo watershed was void of rainforest at this time). 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. ![]() Although debated, it is believed that much of the Amazon reverted to savanna and montane forest (see Ice Ages and Glaciation). The Ice Ages caused tropical rainforest around the world to retreat. 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. During the Ice Age, sea levels dropped and the great Amazon lake rapidly drained and became a river. At this time the Amazon rainforest was born. 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.Ībout ten million years ago, waters worked through the sandstone to the west and the Amazon began to flow eastward. ![]() Gradually this inland sea became a massive swampy, freshwater lake and the marine inhabitants adapted to life in freshwater. 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. Fifteen million years ago, the Andes were formed by the collision of the South American plate with the Nazca plate. By comparison, the Congo Basin has around 168 million hectares of primary forest and 288 million hectares of tree cover, while the combined tropical areas of Indonesia, Papua New Guinea, Malaysia, and Australia have 120 million hectares of primary forest and 216 million hectares of tree cover.Īt one time Amazon River flowed westward, perhaps as part of a proto-Congo river system from the interior of present day Africa when the continents were joined as part of Gondwana. The Amazon is the world's biggest rainforest, larger than the next two largest rainforests - in the Congo Basin and Indonesia - combined.Īs of 2020, the Amazon has 526 million hectares of primary forest, which accounts for nearly 84% of the region's 629 million hectares of total tree cover. WHERE THE AMAZON RANKS AMONG GLOBAL RAINFORESTS The river system is the lifeline of the forest and its history plays an important part in the development of its rainforests. 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 river. 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. 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 - roughly the size of the forty-eight contiguous United States - covers some 40 percent 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. The Amazon River Basin is home to the largest rainforest on Earth. The Amazon Rainforest: The World's Largest Rainforestīy Rhett A.
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