Tropical rainforest

A rainforest is a forest that gets heavy rainfall. The most notable rainforests are in the tropics or subtropics. The biggest rainforest is the Amazon rainforest, which is mostly in Brazil.

Forests like this have extraordinary biodiversity. Over half of all plant and animal species live in the rainforest. Also more than 1/4 of all medicines come from here.^[1] They are an important source of oxygen, but not so much as the seas.^[2][3]

The rainforest gets an average of 50 to 250 inches (1.2-6.3m) of rain through the year. It is warm all year round rarely getting above 34°C (94 °F) or getting below 20 °C (68 °F). It has an average humidity of 77 to 88%. Tropical rainforests occur in three major geographical areas around the world.^[4]

• Parts of South and Central America – the Amazon River basin, and Costa Rica.
• Africa – Congo River basin, with a small area in West Africa; also eastern Madagascar.
• South Asia and Australasia – west coast of India, Assam, Southeast Asia, New Guinea, and Queensland, Australia.

A less-used term is temperate rainforest. For temperate rain forests of North America,^[5] annual precipitation is over 140 cm (55 in), and the mean annual temperature is between 4 and 12 °C (39 and 54 °F). However, definitions in other countries differ. For example, Australian definitions are ecological-structural rather than climatic:

1. Closed canopy of trees which excludes at least 70% of the sky.
2. Tree species which do not require fire for regeneration, but with seedlings able to regenerate under shade and in natural openings.^[6]

This definition would not suit the forests of western North America, and so the term "temperate rainforest" is not so widely agreed. The weather in a rainforest would be humid, which is wet but warm like a greenhouse.

The bottom-most layer gets only 2% of the sunlight. Only plants adapted to low light can grow in this region. The understory layer lies between the canopy and forest floor. It is a home to a number of birds, snakes and lizards as well as predators such as jaguars or leopards on the forest floor. The leaves are much bigger at this level and insect life is abundant.

1. ↑ "Rainforests at Animal Center". Animalcorner.co.uk. 2004-01-01. Archived from the original on 2012-07-08. Retrieved 2012-08-26.
2. ↑ Neil Champion (2006). Tropical rain forests. Black Rabbit Books. p. 23. ISBN 9781583405086.
3. ↑ Zimmer K. 2019. Why the Amazon doesn’t really produce 20% of the world’s oxygen. [1]
4. ↑ Richards P.W. 1996. The tropical rain forest. 2nd ed, Cambridge University Press. ISBN 0-521-42194-2
5. ↑ "A review of past and current research". Ecotrust. Archived from the original on 2016-10-13. Retrieved 2008-10-23.
6. ↑ Floyd A. 1990. Australian rainforests in New South Wales, vol 1. Surrey Beatty & Sons, Chipping Norton, NSW. ISBN 0949324302