Tropical rainforest

Tropical rainforests are dense and warm rainforests with high rainfall typically found between 10° north and south of the Equator. They are a subset of the tropical forest biome that occurs roughly within the 28° latitudes (in the torrid zone between the Tropic of Cancer and Tropic of Capricorn). These forests are known for their thick, tall trees and the variety of life they support.

Tropical rainforests ecosystems are distinguished by their consistent, high temperatures, exceeding 18 °C (64 °F) monthly, and substantial annual rainfall. They are renowned for their significant biodiversity. They are home to 40–75% of all species globally, including half of the world's animal and plant species, and two-thirds of all flowering plant species. Their dense insect population and variety of trees and higher plants are notable.

The structure of a tropical rainforest is stratified into layers, each hosting unique ecosystems. These include the emergent layer with towering trees, the densely populated canopy layer, the understory layer rich in wildlife, and the forest floor, which is sparse due to low light penetration. Many indigenous peoples around the world have inhabited rainforests for millennia, relying on them for sustenance and shelter.

Conservation efforts are diverse, focusing on both preservation and sustainable management. International policies, such as the Reducing Emissions from Deforestation and Forest Degradation (REDD and REDD+) programs, aim to curb deforestation and forest degradation. Despite these efforts, tropical rainforests continue to face significant threats from deforestation and climate change, highlighting the ongoing challenge of balancing conservation with human development needs.

Overview

Tropical rainforests are hot and wet places where it is always warm and rains a lot. The temperature stays above 18 °C all year, and these forests get at least 1,680 mm of rain each year—sometimes even more than 10 meters! Because of so much rain, the soil often does not have many nutrients.

These rainforests are full of life. They are home to half of all the world’s plants and animals. You can find many different kinds of insects, trees, and flowers in just one area. People call rainforests the “world’s largest pharmacy” because many medicines come from plants found there. Sadly, human activities are harming rainforests, making them shrink quickly.

Forest structure

Rainforests have different layers, each with plants and animals that have special ways to live there. The forest floor gets very little sunlight, so only plants that can grow in low light survive. Animals like okapis, tapirs, and gorillas walk here. The understory layer, just above the floor, has shade-tolerant plants and animals like leopards, poison dart frogs, and small mammals. Only about 5% of sunlight reaches this layer.

The canopy is the main roof of the forest, full of tall trees and many different plants and animals, including birds, insects, and monkeys. The emergent layer has the tallest trees that rise above the canopy. These trees can reach heights of up to 55 meters and host unique animals like large birds and bats. The structure of rainforests changes over time as trees fall and create gaps that help new plants grow.

Ecology

Tropical rainforests are found close to the equator, where they experience warm temperatures and lots of rain throughout the year. These forests have special features that help them survive in such a sunny and wet environment. For example, many trees have big, wide roots called buttress roots that spread out near the ground. These roots help trees get nutrients and water quickly, since the soil in rainforests doesn’t hold onto nutrients for long.

Over time, rainforests change and grow after events like storms or when people cut down trees. When forests grow back after being cleared, they are called secondary forests. These young forests gradually become more like the original rainforest, with more types of plants and animals.

Biodiversity and speciation

Tropical rainforests are home to an amazing variety of plants and animals. Scientists and ecologists have long wondered why the tropics are so diverse. One reason is interspecific competition, where many species live close together and compete for resources. Some species may disappear, while others find new ways to survive by using different parts of the forest or eating different foods at different times.

Another idea is the theory of Pleistocene refugia. This theory, proposed by Jürgen Haffer in 1969, suggests that during the last glacial period, rainforests were broken into smaller patches surrounded by non-forest areas. These patches allowed species to evolve separately. When the climate changed and rainforests grew back, the patches joined together again. Scientists continue to study this theory to understand how species in tropical rainforests developed their rich diversity.

Human dimensions

Tropical rainforests have been home to many Indigenous people for thousands of years. Groups like the Indigenous peoples of the Americas, the Congo Pygmies, and tribes in Southeast Asia such as the Dayak people and the Penan people have lived in these areas. These communities often move seasonally and trade valuable forest products like hides, feathers, and honey with people outside the forest.

Rainforests provide many important resources, including foods and spices such as yam, coffee, chocolate, banana, mango, papaya, macadamia, avocado, and sugarcane. These plants originally came from tropical rainforests and are still mainly grown on plantations that were once forests. Rainforests also help keep our planet healthy by supporting wildlife, storing carbon, and influencing weather patterns.

Unfortunately, rainforests face threats from logging and farming, which can harm Indigenous communities and damage the environment. However, tourism, when done responsibly, can help protect these areas by providing money for conservation efforts and raising awareness about the importance of rainforests.

Conservation

Rainforests face many threats that put their future at risk. One big problem is deforestation, where forests are cut down to make space for things like mining, drilling for oil and gas, and farming. Many valuable resources such as gold, silver, coltan, oil, and natural gas lie beneath these forests. While these resources help economies grow, clearing forests often leads to lasting damage. For example, in Ghana, decades of mining have reduced the original rainforest to just 12% of its former size.

Another challenge is climate change. Rainforests help absorb carbon dioxide from the air, acting like giant carbon sinks. When forests are destroyed, this important balance is lost, which can trap more heat in the atmosphere and raise global temperatures. Scientists have shown that removing all rainforests in Africa could increase temperatures there by several degrees.

Efforts to protect rainforests include setting aside land for preservation and finding ways for local communities to use the forest sustainably. One global program, called Reducing Emissions from Deforestation and Forest Degradation (REDD), encourages companies and governments to support rainforest conservation by investing in it as a way to balance out their carbon emissions. These actions help keep rainforests alive for future generations.

Main article: Climate change

See also: Effects of climate change on the tropics