The Amazon River Basin is home to the largest tropical rainforest on earth, which is known as the "lungs of the earth".

Because the tropical rainforest is the "lungs of the earth", it plays an important role in the overall ecological environment of the earth. The tropical rainforest is the most resistant and stable ecosystem on earth, with hot weather all year round, abundant rainfall, extremely insignificant seasonal differences, and extremely fast biological community succession. It is the habitat of more than half of the world's animal and plant species.

The tropical rainforest is undoubtedly one of the most precious resources given by the earth to all living things on the earth. Since more than 25% of modern medicines are extracted from tropical rainforest plants, the tropical rainforest is known as the "world's largest pharmacy". At the same time, the photosynthesis of many rainforest plants is particularly powerful in purifying the earth's air. The oxygen produced by the Amazon rainforest alone accounts for 1/3 of the world's total oxygen, so it has the reputation of "the lungs of the earth".

The main function of the tropical rainforest is to regulate the climate, prevent soil erosion, purify the air, and ensure the orderly circulation of materials in the earth's biosphere.

The annual rainfall in the areas where tropical rainforests are distributed is very high, usually higher than 1800 mm, and in some places it reaches 3500 mm. The annual rainfall is evenly distributed, and it is humid all year round, with a relative humidity of more than 95%. The average annual precipitation is more than 2032 mm, which exceeds the annual evaporation. There is no obvious seasonal change here, and the daytime temperature is generally around 30℃ and the nighttime temperature is about 20℃. Most tropical rainforests are located between 23.5 degrees north latitude and 23.5 degrees south latitude (that is, the area between the Tropic of Capricorn and the Tropic of Cancer). In tropical rainforests, there are usually three to five layers of vegetation, and there are trees up to 150-180 feet above them like tents. The density of the lower layers of vegetation depends on the degree of sunlight penetrating the upper trees. The more sunlight comes in, the greater the density.

Tropical rainforests are typical vegetation of tropical rainforest climate and tropical marine climate. Such as the Amazon Plain and Xishuangbanna in Yunnan.

In the 19th century, German botanist Schinbel extensively collected and summarized scientific discoveries and data in tropical areas, and called the evergreen tall forest vegetation in humid tropical areas tropical rainforests, and scientifically described and explained it from the ecological perspective of the time. Tropical rainforests have unique appearance and structural characteristics, which are clearly distinguished from other forest types in the world.

There are many kinds of plants in tropical rainforests, among which trees have a multi-layer structure; the upper trees are over 30 meters high, mostly typical tropical evergreen trees and deciduous broad-leaved trees, with light-colored, thin and smooth bark, and often have plank-like roots at the base of the tree, and flower branches can grow on old trunks.

The trees have many plank-like roots, many aerial root plants or vines, with obvious system stratification, tall trees, and rich plant varieties; because the weather is warm for a long time and the rainfall is high, the plants can continue to grow, resulting in dense and evergreen growth of trees.

Large woody vines and epiphytes are particularly developed, with certain mosses and lichens attached to the leaves, and woody ferns and large-leafed herbs under the forest. Most trees in the rainforest are dicots, with thick leathery leaves and shallow root systems. The roots used for nutrition are usually only a few centimeters deep. A lot of rainwater in the rainforest is lost due to evaporation from the leaves. The weathering of soil and rocks in tropical rainforests is intense, and the weathering crust can reach 100 meters. Although this type of soil is rich in aluminum, iron oxides, hydroxides and kaolinite, some other minerals are lost due to leaching and erosion. In addition, under conditions of high temperature and humidity, organic matter decomposes quickly and can be quickly absorbed by hungry tree roots and fungi. Therefore, the soil here is actually not fertile.