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Tropical rainforests are spread across the globe along the equatorial zones of Africa, Asia, Australia, and Central and South America. The famous Amazon Rainforest of South America is the world’s largest tropical rainforest.

About the size of the contiguous United States, which does not include Alaska or Hawaii, the Amazon Rainforest covers most of north-western -Brazil and extends into neighbouring countries such as Ecuador and Bolivia.

The second-largest is the Congo Rainforest of Africa. Covering much of the Congo River basin, this wilderness spans six African nations which include Cameroon and the Democratic Republic of Congo. This mosaic of rivers, swamps, and forests, is also home to over 600 plants and over 10,000 animal species!

Next is the Mau forest, the largest of its kind, found in the Rift Valley of Kenya. With a total area of 670,000 acres, it is also known as Kenya’s largest water catchment. The beautiful Sumatran rainforest in Indonesia is yet another tropical ecosystem.

The Pacific temperate rainforests of North America’s Pacific Northwest, Appalachian temperate rainforests, Atlantic Oakwood forest, Valdivian temperate rainforests, Knysna-Amatole coastal rainforests, and the rainforests of New Zealand, Tasmania and southeastern Australia are some of the famous temperate rainforests.

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The fact that Earth and humans are greatly dependent on rainforests for their wellness remains unquestioned. Here are a few reasons why.

Primarily, these ecosystems represent a rich plethora of living and renewable natural resources. They are home to more than half of the world’s total estimated 10 million species of insects, plants, and animals, not to mention its 3000 and more varieties of fruits too! Do you know that the Amazon rainforest alone has more fish species than what is found in the entire Atlantic Ocean?

As for humans, rainforests offer a bountiful supply of essential resources such as basic food supplies, fuel, shelter, industrial raw materials, medicines, spices, etc. making it significantly conducive for everyday survival.

Rainforests are super storehouses of medicinal plants too. For instance, out of the 3000 plants that have been identified by the U.S. National Cancer Institute to be effective against cancer cells, about 70 per cent have been found to grow within these rainforests!

The sheer size of these natural wonders is so huge and unfathomable, that scientists have been able to study only under one per cent of the millions of species found here. Hence, conservation and wise management of these rainforests is the need of the hour if the never ending demands of the world are to be satisfied.

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Imagine a summer that is not hot and sweaty, and winters that are cool and not cold! The climate of the temperate rainforests is characterized by mild summers and winters. Since the temperature remains comparatively low throughout the year, climates are cool and rich in moisture, making it suitable for temperate rainforests to prosper along with the coastal areas. Winter seasons are marked by extreme temperatures resulting in snowfall in the high latitude coastal areas and the North American and East Canadian forests, accounting for its uniqueness in climate pattern.

The soil in temperate rainforests is also unique. The massive plant and animal debris produced in the forests are relatively slow to decompose. This forms a deep layer of humus beneficial for the growth of mushrooms and other fungi.

The fish-eating birds, like the marbled murrelet that inhabit the coastal forests, and the bears and wolves of the Great Bear Rainforest of British Columbia that feed on migratory salmon are irreplaceable links in the nutrient cycle of these temperate rainforests.

As for vegetation, the forest floor is characterized by a unique ‘pit and mound’ micro-topography. The holes left behind by uprooted trees are called pits while mounds are hummocks formed by decomposing log and wood waste and also plant roots that are thickly blanketed by mosses, liverworts, and ferns.

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Well, to understand this, you will have to first sit in a black car that has been parked for a while under the sun. Do you notice that the heat inside the car is simply unbearable?

The darkness within rainforests acts like the black car, absorbing heat from the Sun. Beneath the dense canopy, the forest remains warm and constantly damp. This warm and wet weather causes the evaporation of large quantities of water into the air, resulting in cloud formation.

Since the air above the forest roof is cooler than its hot interiors, the clouds condense and fall as rain. These clouds also drift away to distant mid-latitudes and are seen to cause rainfall even in Europe and Australia. Thus rainforests play a major role in rainfall.

Rainforests absorb large quantities of carbon dioxide from the atmosphere and hold high carbon content in their biomass. When trees are cut down massively, this carbon escapes into the atmosphere as carbon dioxide, a harmful greenhouse gas. Combustion of various fossil fuels and the burning and decomposition of paper and pulp from these forests also increase the rate of carbon dioxide emissions.

Just like the glass of a green-house, this atmospheric carbon dioxide traps heat from the sun. The subsequent rise in overall temperature results in global warming thereby causing drastic changes in the global weather pattern.

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You might be surprised to know that tropical rainforests cover only about 7 per cent of the Earth’s total dry land surface. Yet, they were once referred to as the ‘lungs of the Earth’. Well, the reason is very fascinating.

Tropical rainforests or rainforests in general, play a preponderant role in purifying the air as well as in keeping harmful pollutants at bay. A large percentage of the world’s total oxygen is produced by these rainforests and the Amazon rainforest alone, is estimated to absorb vast quantities of the world’s total carbon emissions that result from various human and other biotic activities. Hence, these rainforests can be said to function much the same way as the human lungs, removing harmful carbon dioxide from the atmosphere while providing oxygen simultaneously.

However, recent evidence suggests that much of the oxygen produced by living plants is used up for the decomposition of dead biotic matter that constantly accumulates within these rainforests. Hence, some scientists believe that their positive contribution to the world’s oxygen supply is considerably exaggerated.

The dark interiors of the rainforests also have the ability to trap and absorb heat from the sun; the thick forest canopy above acting as a protective roof. This shields the trapped heat from escaping into the atmosphere.

No wonder they are called ‘air conditioner’ to the outside world!

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Both rainforests, temperate and tropical, have much in common. They are high in humidity, dense in forest volume, and bustling with organic life. Both variants are home to millions of rare and endangered species of flora and fauna. Then what is it that makes temperate rainforests different? The answer is, their geographical position! Except in Antarctica, the temperate rainforests are found in isolated pockets all over the world. These ecosystems are centred mostly on coastal areas and tall mountain ranges.

In some cases, inland mountainous terrains, which undergo an evident change in elevation, are seen to bring about unique changes in the weather pattern. This, in turn, fosters the growth of temperate rainforests in these areas.

The past many centuries have witnessed massive logging of large and tall trees in temperate rainforests. Thankfully, recent trends have shown a widespread acceptance towards the conservation of these natural wildlife habitats. Taiheiyo evergreen forests of Japan and the Appalachian temperate rainforests of eastern U.S. are two examples of such protected national parks or reserves.

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Rainforests are chiefly of two types: Temperate and tropical. They both receive high rainfall and are filled with thick canopies of tall trees.

Temperate rainforests are those that spread along the temperate zones of the globe and receive an annual rainfall of over 140 cm. They experience moderate temperatures across the year. Climate remains misty and foggy and trees are coniferous and broadleaved. The rainforests along the Pacific coast of Canada and the U.S.A, New Zealand, Tasmania, Chile, Ireland, Scotland, and Norway are temperate.

Tropical rainforests, however, are more warm and wet than temperate types. Distributed along the equatorial zone, between the Tropic of Cancer and Tropic of Capricorn, these ecosystems receive high average temperatures and abundant rainfall that are spread constantly throughout the year.

The lowland equatorial tropical rainforests found along the Amazon Basin (South America), Congo Basin (Central Africa), Indonesia, and New Guinea are embedded with evergreen trees. However, the tropical rainforests found in parts of Southern and Central America, the Caribbean, and West African coasts, and the Indian subcontinent are deciduous and semi-evergreen. Summers are warm and wet here, while winters are cooler and drier.

The Montane tropical forests, sometimes also known as cloud forests, are found in mountainous terrains with a cooler climate.

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You might very well know that the Earth’s axis is slightly tilted and that the climatic behaviour of any geographical area is largely dependent on its position on the globe. For this reason, the regions farther from the equator, in both the northern and southern hemispheres, spend a major part of the year away from the sun. The temperate rainforests in these regions therefore experience distinct climates and ‘dry seasons’ which are less constant in pattern.

On the other hand, tropical rainforests are positioned along the equator and are hence, closer to the sun. The amount of heat received from sunlight and the spread of total annual rainfall remains constant throughout the year and hence, they experience no distinct or dry seasons. The temperature seldom drops below 16 degree Celsius and the annual rainfall received ranges from 406.4 to 1016 cm.

The tropical rainforests of Africa, Central, and South America, Asia, and Australia receive ample sunlight and experience consistent warm and wet weather most of the year. This favourable environment fosters the well-being of both flora and fauna. The characteristic gigantic trees, which form the basic structure of tropical rainforests, can live up to hundreds or thousands of years and attain heights that can range from 18 to 46 metres into the air!

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A rainforest is simply a large geographical area that receives high rainfall and is filled with tall trees. In ecological terms, rainforests can be defined as, “multi-storeyed, closed, broad-leaved forest vegetation with a continuous tree canopy of variable height and with a characteristic diversity of species and life forms”.

Rainforests mainly of two types, the tropical and temperate, are considered to be the Earth’s oldest living ecosystem. They are home to a breath-taking variety of flora and fauna. You might be surprised to know that according to estimates, at least half of the Earth’s plant species, and about 40 to 70 per cent of all biotic species are indigenous to these rainforests! Experts strongly advocate the possibility of the presence of millions of unidentified insects, plants, and animal species still waiting to be discovered! No wonder then, that tropical rainforests are known as ‘Jewels of the Earth’!

The presence of over one-quarter of the world’s natural medicines, make rainforests the world’s ‘largest pharmacy’ too!

However, regions that experience dry seasons, like North-Eastern Australia, which receives an annual rainfall between 800 and 1,800mm, also have rainforests. 75 per cent of the total tree species of these ‘dry rainforests’ are deciduous.

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Rainforests are divided into the following layers, from the top to bottom: Emergent, Canopy, Understorey, and Forest floor.

Emergent layer

This topmost layer has the tallest of trees. Broad-leaved to trap in maximum sunlight, they can rise to an astounding height of about 50 m with trunk perimeters measuring up to 4 m!

Canopy layer

The most important of all layers, its trees have smooth, oval-leaved branches that spread a canopied roof over subsequent layers. Trunks and branches host many epiphytic plants. It is estimated that 50 per cent of the Earth’s plant species and around 25 per cent of its insect varieties thrive in this layer. Snakes, toucans, and tree frogs flourish here because of the abundance of food.

Understorey layer

The amount of sunlight that penetrates to this third layer is minimal and hence, trees have to grow larger leaves to collect as much sunlight as possible. Various insect species and animals such as tree frogs and jaguars (except in Australia) are found in this layer.

Forest floor layer

Of all the layers, this is the darkest one, making it extremely difficult for plants to grow. Biotic matter can decay in a matter of just a few days! Bush turkeys, lyrebirds and the like are found to exist here.

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Because it rains almost every single day! Late most afternoons, the sky goes black and there’s a heavy thunderstorm. Rainforests grow along the equator where it’s hot and sticky all year round. It’s the perfect weather for plants to grow.

Where do the biggest forests grow?

The biggest forests in the world stretch for thousands of kilometres across the north of Europe and Asia. The trees that grow here are conifers. They’re trees with needle-like leaves and cones.

Is it true? The paper we use comes from forests.

Yes. You could make more than 1,500 copies of this book from a single conifer tree.

Amazing! The biggest rainforest grows in South America along the banks of the River Amazon. It’s home to millions of plants and animals.

How do rainforests grow?

Rainforests grow in lagers depending on the height of the trees. The tallest trees poke out above the forest. Below them is a thick roof of tree-tops called the canopy. Next comes a layer of shorter trees, herbs and shrubs.

Tropical rainforests are home to an incredible range of animal life. Over half of the world’s known species exist in the Amazon rainforest alone. Colourful birds, such as toucans, parrots and macaws, live alongside gorillas or other primates, while tigers, pumas and wolves may roam among countless poisonous snakes and insects.

It is said that a single hectare (about two and half acres) of rainforest can contain up to 1500 species of plants plus 750 species of trees. It is this wealth of plant life that attracts and sustains an amazing collection of animals. For example, one in five of all bird species are found in the Amazon rainforest.

Mammals such as Orangutans (in Asia), Gorillas (Africa), Jaguars (South America) and sloths (Central and South America) all call the rainforest home. Sloths spend most of their time in the trees. Their hooked claws and long arms allow them to spend most of their time hanging upside down! Sloths are herbivores and due to their slow movement and metabolism it can take them up to a month to digest their food! Reptiles such as Anacondas, the Emerald Boa Constrictor and the Gaboon Viper slither through the trees and on the forest floor. Insects including cutter ants, tarantulas, scorpions, butterflies and beetles rummage on the forest floor. Amphibians such as frogs and toads live in trees or near bodies of water on the forest floor. Fish including the piranha, Amazonian catfish, fresh water dolphins and stingray inhabit the rivers that run through the rainforests.

Because there are so many animals in the rainforest there is a lot of competition for sunlight, food and space. Animals therefore have to adapt to the environment.

Some animals use camouflage to hide from predators and some predators use camouflage to help them hunt for food. Their colouring or patterned skin help them disappear into the rainforest, blending into the colour of the bark or leaves.

Some animals don’t hide, some use their colouring to warn potential predators away. The poison dart frog is a good example, they may be small but they are one of nature’s most toxic and dangerous creatures. Some local people put the frog’s poisonous toxins on the tips of their blowpipe darts to kill small prey which they then eat.

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With careful planning, areas of rainforest can he re-established, although it takes over a hundred years for the forest to return to its original state. However, it the land is damaged, only scrubby vegetation will grow again.

We all know it takes a long time for cleared rainforests to regenerate, but how long exactly? According to a study focusing on the Brazilian Atlantic forest, certain aspects can return surprisingly quickly – within 65 years. But for the landscape to truly regain its native identity takes a lot longer – up to 4000 years.

The Atlantic forest originally stretched along the southern half of Brazil’s Atlantic coast, covering some 1.2 million square kilometres. Once lush, the forest has been continually exploited for food, wood and space.

Today, land it used to occupy is home to most of the country’s population, including Brazil’s two largest cities, São Paulo and Rio de Janeiro, and only 100,000 square kilometres of forest remain. In 1993, however, the government created several protected areas to conserve the forest’s remnants. To determine how long it would take for the forest to regenerate, Marcia Marques and colleagues at the Federal University of Parana collected data on different parcels of forest that had been virtually cleared and left to recover for varying amounts of time.

The researchers looked at four different measures of forest regrowth: the proportion of tree species whose seeds are dispersed by animals, the proportion of species that can grow in shade, tree height, and the number of native species.

“Animal-dispersed trees sustain a large number of fruit-eating animals, that sustain other animals including large carnivores,” says Marques. “Thus, from the proportion of animal-dispersed trees we can estimate how complex the forest’s ecological web has become.”

Animals are key to the successful regeneration of cleared areas and, typically, 80% of the tree species in a mature tropical rainforest are animal-dispersed. The researchers found that it took just 65 years for a forest to recover to this level.

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The heat and heavy rain in a rainforest are perfect for living things. Trees grow tall and flowers blossom. The lush rainforest provides food and shelter for the millions of creatures that it is home to.

 

 

 

 

 

 

 

 

Rainforests recycle their own water

Every day, the sun heats the rainforest, causing water from trees and plants to evaporate (turn into its gas form – water vapour). As the water vapour rises, it cools and condenses back into liquid water and forms rain clouds. When it rains, the plants soak up rain and the water cycle begins again.

 

 

 

 

 

Continue reading "Inside a rainforest"

 

 

Rainforests are dense, warm, wet forests, with huge trees. They are very special places. Over half the known animals and plants in the world live in rainforests, and new ones are being discovered all the time.

 

 

 

 

 

 

This is a tropical rainforest. It rains here almost every day.

More than two metres of rain falls in a tropical rainforest every year. It is a hot, wet and steamy place with little variation in weather and no seasons. As a result, the trees and plants stay green and keep growing all year round.

 

 

 

 

 

The white areas were once rainforests.

An area of rainforest the size of a football pitch is destroyed every second! They are cut down for their wood, or to make way for farms, mines or roads. These unique and important environments – which affect the world’s weather and provide us with medicine, food and oxygen – could be lost forever.

The green areas on this map show where tropical rainforests grow today.

Most of the world’s rainforests are tropical. They grow in ‘the tropics’, a hot area just north and south of the equator. The equator is the imaginary line we draw around the middle of the earth. Some rainforests grow further north and south of the equator where it is cooler. These are temperate rainforests.