RAIN FORESTS

What are rain forests  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), [1]  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 rainforests. [2]  It 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 there. [3]  Rainforests are also responsible for 28% of the world's  oxygen  turnover, sometimes misname