The Tropical Rainforest

Rain forest on Ko Yao Noi Island, Thailand. (Michael Cory/Wikimedia Commons/CC BY 2.0)

All tropical rainforests have similar characteristics including climate, precipitation, canopy structure, complex symbiotic relationships and an amazing diversity of species. However, not every tropical rainforest can claim exact characteristics when compared by region or realm and there are rarely clear defining boundaries. Many may blend with adjoining mangrove forests, moist forests, mountain forests, or tropical deciduous forests.

Tropical Rainforest Location

Tropical rainforests mainly occur inside the world's equatorial regions. Tropical rainforests are restricted to the small land area between the latitudes 22.5° North and 22.5° South of the equator - between the Tropic of Capricorn and the Tropic of Cancer.

The global distribution of the tropical rainforest can be broken into four continental regions, realms or biomes: the Ethiopian or Afrotropical rainforest, the Australiasian or Australian rainforest, the Oriental or Indomalayan/Asian rainforest, and the Central and South American Neotropical.

Importance of the Tropical Rainforest

Rain forests are "cradles of diversity." They spawn and support 50 percent of all living organisms on Earth even though they cover less than 5% of Earth's surface. A rainforest's importance is truly incomprehensible when it comes to species diversity.

Losing the Tropical Rainforest

Just a few thousand years ago, tropical rainforests are estimated to have covered as much as 12% of the land surface on earth.

This was about 6 million square miles (15.5 million square km).

Today it is estimated that less than 5% of Earth's land is covered with these forests (about 2 to 3 million square miles). More importantly, two-thirds of the world's tropical rainforests exist as fragmented remnants.

The Largest Tropical Rainforest

The largest unbroken stretch of rainforest is found in the Amazon river basin of South America.

Over half of this forest lies in Brazil, which holds about one-third of the world's remaining tropical rainforests. Another 20% of the world's remaining rainforest exists in Indonesia and the Congo Basin, while the balance of the world's rainforests is scattered around the globe in tropical regions.

Tropical Rainforests Outside the Tropics

Tropical rainforests are not just found in tropical regions, but also in temperate regions like Canada, the United States, and the former Soviet Union. These forests, like any tropical rainforest, receive abundant, year-round rainfall, and are characterized by an enclosed canopy and high species diversity but are without the year-round warmth and sunlight.


An important characteristic of tropical rainforests is moisture. Tropical rainforests usually lie in tropical zones where solar energy produces frequent rainstorms. Rainforests are subject to heavy rainfall, at least 80" and in some areas over 430" of rain each year. High volumes of rain in rainforests can cause local streams and creeks to rise 10-20 feet over the course of two hours.

The Canopy Layer

Most of life in the tropical rainforest exists vertically in the trees, above the shaded forest floor - in the layers.

Each tropical rainforest canopy layer harbors its own unique plant and animal species interacting with the ecosystem around them. The primary tropical rainforest is divided into at least five layers: the overstory, the true canopy, the understory, the shrub layer, and the forest floor.


Tropical rainforests are not all that pleasant to visit. They are hot and humid, difficult to reach, insect infested, and have wildlife that is hard to find. Still, according to Rhett A. Butler in A Place Out of Time: Tropical Rainforests and the Perils They Face, there are undeniable reasons to protect the rainforests:

  • Loss of local climate regulation - "With forest loss, the local community loses the system that performed valuable but unnoticed services like ensuring the regular flow of clean water and protecting the community from flood and drought. The forest acts as a sort of sponge, soaking up the tremendous amounts of rainfall brought by tropical downpours, and releasing water at regular intervals. This regulating feature of tropical rainforests prevents destructive flood and drought cycles."
  • Erosion and its effects - "The loss of trees, which anchor the soil with their roots, causes widespread erosion throughout the tropics. Only a minority of areas have good soils, which after clearing are quickly washed away by the heavy rains. Thus crops yields decline and the people must spend income to import foreign fertilizers or clear additional forest."
  • Loss of species for forest regeneration - "A fully functioning forest has a great capacity to regenerate. Exhaustive hunting of tropical rainforest species can reduce those species necessary to forest continuance and regeneration."
  • Increase of tropical diseases - "The emergence of tropical diseases and outbreaks of new diseases including nasty hemorrhagic fevers like Ebola and Lassa Fever is a subtle but serious impact of deforestation."
  • Destruction of renewable resources - "Deforestation can rob a country of potential renewable revenues while replacing valuable productive lands with virtually useless scrub and grassland (desertification)."