Rainforests are forests characterized by high rainfall, with annual rainfall in the case of tropical rainforests between 250 and 450 centimetres, 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. There may be many millions of