Tropical rainforests have an average temperature between 20-35°C and receive heavy rainfall between 200-400cm annually. Over 50% of all life exists in these forests, which only take up 2% of the earth's surface. The forests grow on acidic, nutrient-poor soils and have a structure with multiple layers - a forest floor, understory, and canopy or overstory. Fig trees are crucial to the forests as they provide a food source for birds and mammals through their fruits, and army ants that travel across the forest floor in swarms are followed by birds eating the debris left behind.