Tropical Rainforest Biome

The tropical rainforest biome is an ecosystem full of plants and animals. The largest are found in South America, the Congo River Basin (western Africa), and throughout much of southeast Asia. Tropical rainforests cover 7% of the Earth’s surface.

Tropical Rainforests

Tropical rainforests are some of the most dynamic natural areas on Earth. The tropical rainforests around the world offer habitat for 3 to 50 million animal species, almost 50% of all animals on the planet. The vibrant plants and trees supply much of the world’s oxygen and many medicines too.

Each plant and animal that lives in a tropical rainforest find a habitat interdependent with other plants and animals within the tropical rainforest.

Tropical rainforests are forests that grow near the Equator.  They have many trees, and the climate is warm and has lots of rain.  Due to all of the rain, the trees grow very tall, and so the sunlight has a hard time reaching the ground.

The climate of the tropical forest does not change much, so with the rain and the hot temperatures, it is a busy biome for animals, especially those that live in trees.

Tropical Rainforest Biome Facts:

• Two-thirds of all plant life on Earth lives in a Tropical Rainforest Biome.
• The soil in the rainforest does not have many nutrients.
• There are thousands of butterfly species found in the Tropical Rainforest Biome.
• The Tropical Rainforest Biomes are getting lost because of logging, mining and slash and burn agriculture practice.
• Nocturnal animals live during the night and diurnal animals live during the day.
• Epiphytes like orchids are plants that grow on other plants.
• The largest Tropical Rainforest Biome in the world is the Amazon Basin in South America.
• Three other rainforests are called Montane or cloud forests, Mangrove forests, and Monsoon forests.
• The tropical rainforests makes up around 6-8% of the Earth’s surface.
• More than half of the animal species in the world live in the Tropical Rainforest Biome.
• There are six layers in a Tropical Rainforest Biome called subterranean, forest floor, shrub layer, understory, canopy, and the emergent layer.
• Tropical Rainforest Biome receives abundant sun because they are located near the Equator which is 0° Latitude
• Twenty-five percent of all medicines in the world include an ingredient from a Tropical Rainforest Biome.
• There are more than 3,000 edible fruits in Tropical Rainforest Biomes.
• More than 30,000 species of orchids live in Tropical Rainforest Biomes.
• The Tropical Rainforest Biome is important because it helps to produce oxygen and medicines for the whole world.
• The three main areas of Tropical Rainforests in the world are called the Neotropical, African, and Indo-Malaysian.
• A Tropical Rainforest Biome must receive 75-100 inches (1,750 mm to 2,500 mm) of rain a year spread out throughout the year.
• There is a tremendous amount of humidity in Tropical Rainforest Biomes because of evapotranspiration caused by photosynthesis.
• Some plants and animals can only survive in a specific layer of a Tropical Rainforest Biome.

Where are tropical rainforests found?

There are three distinct natural zones, also known as biomes on our planet. The biomes are called polar, tropical, and temperate. The zones are divided by imaginary lines called latitude lines. The imaginary lines run east and west along with the planet.

Polar zones are found in the north and south regions of the planet between 66° and 90° latitude. Temperate regions are located between 66° and 23° latitude. Tropical zones are found between the Tropic of Cancer at 23° north latitude to the Tropic of Capricorn at 23° south latitude. The Equator splits the two tropics at 0° latitude.

Tropical rainforests are found within the tropical regions of the world. The unique rainforests account for 6-8% of the landmass on Earth. Tropical rainforest biomes are found in Central America, South America, Southeastern Mexico, Equatorial Africa, the Pacific Islands, Caribbean Islands, Western India, Northeastern Australia, and much of Southeast Asia.

The tropical rainforests around the world are found in three distinct regions. The Neotropical composed of South America, Central America, Southeast Mexico, and the Caribbean. The African region contains Africa and Madagascar.

The Indo-Malaysian region is composed of India, Southeast Asia, the Pacific Islands, and Australia. The Amazon Basin is the largest tropical rainforest in the world and is located in South America.

What Defines a Tropical Rainforest Biome?

When a person defines a biome, they are interested in the abiotic factors. Abiotic factors are non-living factors such as rainfall or precipitation, temperature, soil nutrients, and sunlight.

Rainfall

Consistent rainfall is necessary to help sustain the large amounts of plant life within a tropical rainforest. There are two factors that help define the tropical rainforest.

First tropical rainforests biomes must receive more than 75 inches (1900 millimeters) of rain in a year with some tropical rainforests receiving well over 100 inches (2500 millimeters) of rainfall per year.

The second factor is rainfall must occur throughout the year. Some tropical rainforests do experience a dry season, but rainfall still occurs throughout the year.

Here is a quick look at the annual rainfall in distinct regions of tropical rainforests:

• Amazon Basin – Between 1,500 mm and 3,000 mm
• Congo River Basin – Between 720 mm and 2,115 mm
• Southeast Asia Rainforest – Between 800 mm and 2,006 mm

Temperature

Tropical rainforests are very warm.  The tropical rainforest biomes have a temperature that ranges from 70° F to 85° F (21° C to 30°C). The stable temperatures in a tropical rainforest allow for plants and animals to flourish throughout the year.

Humidity

The high temperatures, steady rainfall, and large amounts of living organisms create extreme humidity within a tropical rainforest. Humidity is the byproduct of evapotranspiration. Evapotranspiration is when water is evaporated into gas and is transpired into the atmosphere when during the photosynthesis process of plants.

As a result, tropical rainforests generally have a humidity rate of 77% to 88% throughout the year due to the large amounts of plant life, which also contributes to high biodiversity within the rainforests. One interesting fact about evapotranspiration is that it helps tropical rainforests create rain when the water evaporates upward and condenses in the cooler air, which in turn returns to the tropical rainforest as rain.

Soil Nutrients

People would think with a large amount of plant life and biodiversity that tropical rainforests have soil full of nutrients. That is not the case. The soil within tropical rainforests is nutrient-poor and has of the lowest nutrients for plants in all of the biomes.

Poor nutrient soil is created by large amounts of rainfall. The rainfall cleanses the soil of most nutrients. What nutrients are left in the soil is rapidly devoured by a large number of plants within the tropical rainforests. There is a large number of leaves, fallen trees, and other dead material, which generally help increase the nutrients in the soil.

But this material along the rainforest floor called litter is decomposed rapidly by the high temperatures, humidity, and dead organisms like insects. What nutrients are left is then consumed fast by living plants leaving the soil nutrient-poor in the end.

Sunlight Hours

Tropical rainforests are located between the Tropic of Cancer and the Tropic of Capricorn. The Equator is in the center of the two tropics. Sunlight is consistent throughout the year in this region of the world.

There is no real summer or winter like the biomes in the north and south portions of the world. Sunlight pours down on tropical rainforests allowing for plants to photosynthesize. But very large trees control most of the sunlight. The tall trees prohibit much of the sunlight from directly reaching the forest floor.

The Six Layers of a Tropical Rainforest Biome

The layering of a tropical forest is important for animals and plants to survive interesting. Each layer plays an important factor to the survival of a tropical rainforest. Many organisms such as plants and animals may use several different layers to their advantage to survive.

Other organisms reside only within a certain layer of the tropical rainforest during their existence. Layers within a tropical rainforest are directly affected by the amount of sunlight that reaches that particular layer. Sunlight also affects the interaction between animals and plants as well as interactions between different animals.

The layers of the tropical rainforest are not necessarily cut and paste from one area of the tropical rainforest to another area. Researchers believe there are six basic layers within a tropical rainforest which are subterranean, forest floor, shrub layer, canopy, and the emergent layer.

Here is a quick rundown on the different aspects of each tropical rainforest layer:

Subterranean

The subterranean layer exists under the soil. People don’t really see this layer and sometimes forget the activities that take place underground. Even though tropical rainforests contain poor soil without many nutrients, there is still plenty of life.

Fungi and insects like ants live in this layer. Many of the ants are blind or have very little vision. They can spend their whole life in the dark hunting other insects underground.

Forest Floor

The forest floor of a tropical rainforest is considered the second layer. The layer receives only 1-2% of the total sunlight because of the towering trees and shrubs. On the forest floor you can expect to find organisms that do not require direct sunlight.

Shade tolerant plants like ferns and reptiles like snakes and frogs and some mammals such as pigs, bats, and large cats like jaguars flourish in this layer. Over time gap dynamics take place. Gap dynamics involve gigantic trees falling to the forest floor allowing for new plants to thrive on the sunlight.

Shrub and Understory

The shrub and understory layer does not receive much sunlight either. Plants and trees do not grow very tall. Plants and trees in this layer generally have broader leaves to help gather sunlight.

Weather conditions are different with little to no wind and the humidity levels are higher. In this layer you can expect to find more reptiles such as snakes and frogs. Birds that eat insects called insectivorous thrive in this layer by eating the insects on the trees, shrubs, and forest floor.

Canopy

The canopy is the top layer of the trees.  The big trees are usually over 100 feet (33 meters) tall. The leaves form a canopy or umbrella with each tree having a top diameter around 19 feet (six meters).

The layer captures sufficient sunlight allowing for plenty of leaves, flowers, and fruit. The layer is also the most populated by animals. Birds like toucans eat the fruit and you can expect to see plenty of monkeys, snakes, frogs, and other mammals like sloths.

Some of these animals will live their entire life in the canopy where they find plenty of food, water, and sunlight.

Emergent Layer

The trees within the emergent layer receive the most sunlight of all layers. The gigantic trees grow to heights of more than 196 feet (60 meters). The leaves on these trees are generally waxy and thinner to protect them from the added sunlight.

There are fewer leaves and branches on these big trees but are spread out more over the canopy layer. The layer is less populated than the canopy layer. Life in this layer includes habitat suitable for monkeys, birds of prey, and butterflies.

There are also some flowers and fruit that are consumed by animals.

Different Types of Rainforest

Although there are numerous different rainforests around the world, we are focusing on tropical rainforests. There are a few different types of tropical rainforests around the world. To this point, the discussion is centered on lowland evergreen rainforests and semi-evergreen rainforests.

Lowland evergreen rainforests have a high diversity of plants and animals as well as the same rainfall throughout the year. Semi-evergreen rainforests experience a specific period of drought each year; have a mixture of evergreen trees and deciduous trees as well as a lower diversity of plants and animals.

Here is a quick look at other types of tropical rainforests around the world:

Montane rainforests – exist in places with higher altitude. The weather is cooler, the trees are shorter in height, and there are different plants. The montane rainforests don’t have many vine plants and the trees don’t have protections as we see in lowland evergreen and semi-evergreen rainforests. A good example of a montane rainforest is found in Costa Rica.

Mangrove rainforests – thrive along rivers that are in direct contact with an ocean or sea. Mangrove rainforests don’t contain or have very little distinct layering and the roots grow underwater meaning there is no forest floor.

Trees like a Red Mangrove live in a mixture of salt and freshwater also known as brackish water. The trees can survive the harsh conditions created by the different types of water. A good example of a mangrove rainforest is found in Southeast Mexico and several Caribbean Islands.

Monsoon rainforests – are created by monsoons or periods of heavy rainfall. Monsoon rainforests also experience a period of drought throughout the year. Growing conditions are much different and you can expect to see more deciduous trees and less diversity of animals.

Biodiversity

Biodiversity within a tropical rainforest is tremendous. Two-thirds of the world’s plants live within tropical rainforests. Almost one-half of all animals in the world also live within tropical rainforests. Tropical rainforests exist around the world and the biodiversity of each tropical rainforest is unique to their area of the world.

The Neotropical contain the most biodiversity followed by the Indo-Malaysian rainforests and the African rainforests have the least biodiversity of the three zones.

As in other natural biomes of the planet, tropical rainforests exhibit specific species of plants and animals that are endemic to the surrounding area.

For instance, you can see primate mammals in all three tropical rainforests but they are of different species. The same goes for plants where you might find a specific fern in a Neotropical rainforest and not in an African rainforest.

Plants within a Tropical Rainforest Biome

More than two-thirds of all plants on the planet live within a tropical rainforest biome. Tropical rainforests supply plants with almost perfect living conditions. Plants have plenty of water and lack the conditions of a seasonal forest area with temperate deciduous trees.

The plants in the tropical rainforests due to lack nutrients from the soil and are subject to extreme heat which causes a tremendous amount of evapotranspiration. Another factor for plants is the lack of sunlight many plants experience within the different layers of a tropical rainforest.

Trees control the environment within a tropical rainforest. Due to the insufficient nutrients in the soil, trees have deep roots and cover much of the forest floor forming a system to gather the necessary nutrients.

Tropical rainforest trees also have a different type of bark which is thinner and waxy. The trees do not need the heavier bark like a tree in a colder climate. Their leaves are thinner and waxy too. The leaves help water escape in order to fight off moldy conditions in the high humidity. One problem for trees is the lack of wind in the canopy. The wind helps spread the tree’s seeds.

However, seeds are distributed by animals eating the fruit or flowers of the trees and then releasing the seeds when they go to the bathroom. There are more than 3,000 edible fruits that grow within tropical rainforests around the world.

Besides trees, there are other interesting plants in tropical rainforests such as epiphytes. Orchids are the most common epiphyte within a tropical rainforest. There are more than 30,000 different species of orchids around the world.

Epiphytes are plants that live directly on other plants thriving on the nutrients from the host tree or plant. Some of the epiphytes never touch the forest floor throughout their lifetime. Other plants like semi-epiphytes grow differently too.

The plants start growing while in the canopy and their roots stretch down to the forest floor layer of a tropical rainforest.

Flowers thrive in a tropical rainforest. Besides orchids, you can expect to find thousands of species of bromeliads that are similar to the pineapple family. Some bromeliads hold gallons of water in their waxy flower petals. At times the flowers provide a unique ecosystem that is home to insects, spiders, snails, and even scorpions.

Another important aspect of the plants that grow in a tropical rainforest is their medicinal value. Sure the oxygen helps us breathe but 25% of all medicines around the world include an ingredient or plant from a tropical rainforest.

Animals of a Tropical Rainforest Biome

Some researchers estimate that there are more than 50 million animal species within tropical rainforests around the world. Each species requires a different habitat within the tropical rainforests. Species live in all of the six layers found within a tropical rainforest.

Animal species within each layer live a different lifestyle and utilize different times throughout the day to gather nutrition from the tropical rainforest. The different eating habits of animals allow for less competition at specific times during a given day.

The lack of competition gives the animals a better chance of survival.

Animals that hunt or live during the daylight hours are called diurnal. Some primates or monkeys can only thrive during the day. Their eyesight is enhanced with sunlight and they can gather fruit or other nutrients.

Diurnal animals usually have weaker eyesight at night which gives predators a better chance when they are hunting for nutrition.

Many of the tropical rainforests come to life with animals in the night time. Nocturnal Animals that are Thousands of species prowl the forest floor for food at night like jaguars, pigs, snakes, and frogs.

Other nocturnal animals like bats thrive on insects and feed off fruit and flowers in the darkness. Bats have poor eyesight and use a sonar system to find their prey or fruit for nourishment.

Poisonous animals find plenty of useable habitats within tropical rainforests too. There are thousands of poisonous species from reptiles to birds to insects. Brightly colored frogs are some of the most dangerous and large snakes like anacondas consume large pigs and other predators.

Animals in the tropical rainforests survive by mimicking other animals. The animals can camouflage themselves to appear like a poisonous animal or they blend into the environment like tree bark or pedals of a plant.

Large predators like jaguars also use mimicry to hunt and blend into the natural landscape to sneak up on their prey.

The Importance of Rainforests

Tropical rainforests around the world play an important role in modern society. With its vast diversity of organisms from plants to animals, tropical rainforests are a haven for ecotourism experiences.

More importantly tropical rainforests provide the world with most of its oxygen. Besides oxygen the unique plants play an important role in developing medicines and the edible plants help feed the world.

Specific insects within a tropical rainforest provide protection from crop devastation in a normal agricultural setting. In addition, the tropical rainforests are home to hundreds of various indigenous tribes that live off the unique plants and animals’ inharmonious way.

The tropical rainforests are also under attack on a daily basis. The trees are cut by illegal loggers, the land is reclaimed for agriculture with a slash and burn practices, endangered species are hunted for trophies, and mining is polluting the river systems.

The threats to the tropical rainforests affect everyone on the planet. Imagine losing an animal species or a specific plant that could cure cancer before proper research was completed. If you are an indigenous person you are forced to start a different lifestyle as your habitat becomes smaller and smaller with less traditional food available.

For the reasons above there are people, governments, and organizations around the world fighting to keep the tropical rainforests intact. Without the amazing biodiversity of the tropical rainforests the life we enjoy today would suffer on many levels.

What did you learn?

• What is a Tropical Rainforest Biome? The Tropical Rainforest Biome is a biome between the Tropic of Cancer (23° N Latitude) and the Tropic of Capricorn (23° S Latitude).
• What are the main causes of destruction within a Tropical Rainforest Biome? Thousands of acres of Tropical Rainforest Biome are lost due to illegal logging, mining, and slash and burn agriculture practices.
• What is different about the weather in the tropical rainforest biome?
  In the tropical rainforest biome, there is a lot of rain.  The average rainfall per year is 75-100 inches (1,750 mm to 2,500 mm).
• What are the names of the three main Tropical Rainforest Biomes? The three main areas of Tropical Rainforest Biomes are called the Neotropical, African, and Indo-Malaysian.
• What are the six layers of the rainforest?
  The six layers of the rainforest are the emergent layer, canopy, understory, shrub layer, the forest floor, and the subterranean layer.
• Why does the forest floor get very little rain and have very few plants?
  The forest floor does not get much rain or sunshine because the canopy blocks it.  This is why there are fewer plants that are found on the ground.
• Are there many animals found in the Tropical Rainforest Biome?  
  More than half of the animals in the world live in the Tropical Rainforest Biome.
• What elements define a Tropical Rainforest Biome? There are four elements that define a Tropical Rainforest Biome which are precipitation (rainfall), temperature, soil nutrients, and sunlight.
• What percentage of plants around the world is found within a Tropical Rainforest Biome? Two-thirds of all plants in the world are found within a Tropical Rainforest Biome.
• How many medicines rely on plants from a Tropical Rainforest Biome? Twenty-five percent of all medicines include an ingredient found within a Tropical Rainforest Biome.

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