Rainforests can be described by two words: hot and humid. Mean monthly temperature will exceed 18 degrees Celsius (64 degrees Fahrenheit) during the year. Average annual rainfall is not less than 168 cm (66 inches) and can exceed 1,000 centimeters (390 inches), although it is generally between about 175 cm (69 inches) and 200 cm (79 inches). High rainfall like this often make poor soil nutrients due to the soluble nutrients often washes away.
Rainforests represent the level is very high biodiversity. Approximately 40% to 75% of all species are native. Rain forest is also home to a half of living things and the truth of both species of the planet. Two-thirds of all species of flowering plants can be found in the rain forest. One hectare of rainforest may have 42000 different insect species, approximately 807 trees in 313 species and 1,500 plant species grow higher. Rainforests also known as "the world's largest drug warehouse", because over one quarter of natural medicines have been found there. It seems that even millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests.
Rainforests are among the ecosystems most threatened in the world due to the split cutting large scale by human activities. Habitat fragmentation caused by geographical processes such as volcanic activity and climate change occurred in the past, and has been identified as the most important cause of species formation. However, the destruction of habitat caused by human quickly suspected of being one of the main causes of the extinction of species. Rainforests have been targeted for logging and forest clearing for large-scale agricultural land during the 20th century, and the area is covered by rainforests around the world are rapidly diminished.
rainforests have existed on earth hundreds of millions of years. Most of today's tropical rainforest located on the array of Gondwana, Mesozoic. Mainland fragmentation have caused huge loss of amphibian species, at the same time drier climate spurred the diversification of reptiles. The division has left the tropical rain forest in the five key areas of the world: America, Africa, Southeast Asia, Madagascar, and New Guinea, with a smaller portion located at the outer edge of Australia. However, the details of the origin of rain forests is still uncertain because the fossil record is incomplete.
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