A count of the number of rain forests left in the world is not available, but as of 2014, rain forests account for less than 2 percent of the Earth and are habitat for 50 percent of animals and plants. Several thousand years ago, rain forests covered about 12 percent of the Earth, or 6 million square miles. The largest continuous rain forest is near South America's Amazon river.
About 20 percent of the world's rain forests are in the Congo Basin and Indonesia, and the rest are in tropical regions around the world. Rain forests typically receive between 90 and 177 inches of rainfall each year. Climate conditions necessary for rain forests are largely created by the monsoon trough, an area where wind patterns of the Southern and Northern Hemispheres meet. Tropical storms frequently form near monsoon troughs and can quickly produce high levels of rainfall.
Between 40 and 75 percent of all species of plants and animals in the world are native to rain forests, and millions of undiscovered species may exist there. One-fourth of natural medicines have been discovered in rain forests, and the plant life found there cause more than 25 percent of the planet's turnover of oxygen by processing through photosynthesis. Jungles occur when low areas of rain forests do not get enough sunlight and tangled vines and shrubs take over.