Tropical rainforest used to be called Hylace, Jungle, Brush, Urwald, Tropical ombrophilous forest, etc. At the end of the 19th century, Andreas Franz Wilhelm Schimper (1856-1901), a German ecologist and botanist, coined the term “tropical rainforest” to describe the evergreen, tall forest vegetation of the humid tropics after extensive research into the forests of the West Indies, Brazil, Africa and Southeast Asia, and a comprehensive summary of scientific findings and data about certain tropical regions. Simberl further defined the tropical rainforest as “an evergreen formation of wet habitats, 98 ft (30 m) or taller, with many lianas and epiphytes”. Such a vivid, specific and scientific description was later widely recognized and accepted by the academic community, and the name “tropical rainforest” has been used ever since.

Tropical rainforests have served as refuges for many ancient species, especially during glaciations of the Quaternary, when rainforests were not affected by the climate back then. As a result, tropical rainforests harbor the greatest biological gene pool in the world and play a major role in regulating global carbon fluxes and stocks. According to statistics, there are about 250,000 species of green flowering plants in the world, of which 170,000 species are found in the tropics (including 80,000 species in America, 35,000 in Africa and 40,000 in Asia). Tropical rainforests are the most mysterious, beautiful, complex, powerful, stable and perfect forest ecosystems among the Earth’s terrestrial ecosystems. In tropical rainforests, there are still an incredible number of biological and natural laws that have not been fully understood. In particular, little is known about the remarkable richness of tropical rainforest species and the geographical ranges of most rainforest plant species. Neither of them can be explained by Darwin’s theory of evolution.

Tropical rainforests are found across the world between North and South of the Equator, covering regions in America, Asia, Africa and Oceania. Rainforests usually occur in regions with a hot climate, abundant rainfall all year round, and very little seasonal change. Most of the world’s tropical rainforests are distributed in areas where the average annual temperature is above 26°C, the average monthly temperature is over 18°C, and the total annual rainfall is more than 2,000 mm. Several thousand years ago, tropical rainforests were estimated to cover 12% of the Earth’s surface. Due to large-scale industrial logging and irrational utilization of tropical forests, the rate of tropical rainforest destruction is escalating worldwide to 12 million hectares a year, of which tropical rainforests in Asia are disappearing more rapidly than any others on Earth. Half the world’s rainforests have been razed and cover only less than 7% of the Earth’s land surface. Today, fragmented rainforests have replaced continuous tracks of rainforest in two-thirds of the regions. The destruction of a large area of tropical rainforests has resulted in the loss and degradation of wildlife habitats. In tropical Africa, 65% of the wildlife habitat has been lost. Likewise, an alarming 67% decline is reported in tropical Asia, among which 31% of some primates in Southeast Asia have lost their homes, while only 1.2%-22.9% are under protection. The hot, damp conditions in tropical areas allow for the rapid decomposition of organic matter and increasing circulation of materials. The shrinking of the tropical rainforest could have significant impacts on the ecosystem, ranging from soil erosion to habitat degradation, droughts, and the mass extinction of species, especially species with extremely small populations.

Tropical rainforests are geographically located between the latitudes 5-15°N and 10-25°S of the equator. In the book The Tropical Rain Forest: An Ecological Study, British botanist P.W. Richards divides global rainforests into three biomes: American rainforests, African rainforests, and Indo-Malayan rainforests. Among them, the tropical rainforests in Americas cover the largest area. The rainforest along the Amazon River basin is bordered by the Andes Mountains to the west, Guyana to the east, Bolivia and Paraguay to the south, and southern Mexico and the Antilles to the north. Brazil has 481 million hectares of tropical rainforest, the most of any country in the world. African tropical rainforests are mainly found in the Democratic Republic of Congo (177 million hectares), Gabon, Congo, Cameroon, Ghana, etc. The Indo-Malay rainforest, also known as the Asian rainforest, makes up the smallest share. It encompasses areas from Indonesia to Malaysia, Papua New Guinea, Thailand and India. In Indonesia alone, the area of tropical rainforests amounts to 127 million hectares, while the rest of the Asian countries have tropical rainforests of less than 100 million hectares, only tens of millions or even millions of hectares.

The distribution of tropical forests in China is limited to areas in the northern edge of the tropical zone of Asia, including Hainan Island, southern Yunnan and the lower reaches of the Brahmaputra River in southeastern Tibet. At present, the actual area of pristine tropical rainforest in China is estimated at 2-3 million hectares, less than 2‰ of the world’s total. And the Hainan tropical rainforest covers a total area of 670,000 hectares, accounting for about 1/3 of the rainforest in China.