How does the rainforest come into being

Huge areas of the Amazon rainforest were grassland until just 2,000 years ago, it has been revealed.

Researchers say the find sheds new light on the Amazon's history - and show it was a savannah rather than the high forest it is today.

They believe much of the area was grassland until a natural shift to a wetter climate about 2,000 years ago let the rainforests form, according to a study that challenges common belief that the world’s biggest tropical forest is far older

 

The arrival of European diseases after Columbus crossed the Atlantic in 1492 may also have hastened the growth of forests by killing indigenous people farming the region, the scientists wrote in the U.S. journal Proceedings of the National Academy of Sciences (PNAS).

'The dominant ecosystem was more like a savannah than the rainforest we see today,' John Carson, lead author at the University of Reading in England, said of the findings about the southern Amazon.

Rainforests are forests characterized by high rainfall, with annual rainfall in the case of tropical rainforests between 250 and 450 centimetres (98 and 177 in), and definitions varying by region for temperate rainforests. The monsoon trough, alternatively known as the intertropical convergence zone, plays a significant role in creating the climatic conditions necessary for the Earth's tropical rainforests.

Around 40% to 75% of all biotic species are indigenous to the rainforestsIt has been estimated that there may be many millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests. Tropical rainforests have been called the "jewels of the Earth" and the "world's largest pharmacy", because over one quarter of natural medicines have been discovered thereRainforests are also responsible for 28% of the world's oxygen turnover, sometimes misnamed oxygen production, processing it through photosynthesis from carbon dioxide and consuming it through respiration.

The undergrowth in some areas of a rainforest can be restricted by poor penetration of sunlight to ground level. If the leaf canopy is destroyed or thinned, the ground beneath is soon colonized by a dense, tangled growth of vines, shrubs and small trees, called a jungle. The term jungle is also sometimes applied to tropical rainforests generally

Tropical rainforests are forests with tall trees, warm climates, and lots of rain. In some rainforests it rains more than one inch nearly every day of the year!

Rainforests are found in Africa, Asia, Australia, and Central and South America. The largest rainforest in the world is the Amazon rainforest in South America.

WHERE ARE RAINFORESTS LOCATED? Rainforests are found in the tropics, the region between the Tropic of Cancer and the Tropic of Capricorn, just above and below the Equator. In this tropic zone the sun is very strong and shines about the same amount of time every day all year long, keeping the climate warm and relatively stable.

Many countries have tropical forests. The countries with the largest areas of tropical forest are (in order):

    Brazil
    Congo (Democratic Republic)
    Peru
    Indonesia
    Colombia


Other countries that have large areas of rainforest include Bolivia, Cameroon, Central African Republic, Ecuador, Gabon, Guyana, India, Laos, Malaysia, Mexico, Myanmar, Papua New Guinea, Republic of Congo, Suriname, and Venezuela.