Download tropical rainforests

Geography: Grade 6
Climate and Vegetation Regions of the World: Tropical Rainforests
TROPICAL RAINFORESTS
The Main Biomes (Vegetation Regions)
A biome is a large geographical area with distinctive plant and animal groups, which are
adapted for that particular environment. The climate and geography of the area determines
the biome.
Each biome consists of many ecosystems that have adapted to the climate and the
environment. Any change in the ecosystem, can impact other biomes in other parts of the
world.
Vegetation across the world is divided into the following biomes:
• The Forest Biome
◦ Tropical Rainforests
◦ Deciduous Forests (trees that shed their leaves annually)
◦ Coniferous Forests (evergreen cone-bearing trees or shrubs)
• Savannah Biome
• Grasslands Biome
• Desert Biome
• Tundra Biome
Tropical Rainforest
Deciduous Forest
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Coniferous Forest
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Geography: Grade 6
Climate and Vegetation Regions of the World: Tropical Rainforests
Savannah
Grasslands
Desert
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Tundra
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Climate and Vegetation Regions of the World: Tropical Rainforests
The pie graph below shows the breakdown of land area of the different biomes:
The Forest Biome
Through the ages people have been dependent on forests for shelter, food, wood for their
houses, weapons and energy.
Wooden Roof Beams
Latex (Rubber) from Trees
Trees Provide Us With Food
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Trees Provide Us
With Fuel
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Climate and Vegetation Regions of the World: Tropical Rainforests
The forest biome is dominated by various tree species. In some forests, the dense canopy of
the treetops grows so closely that sunlight cannot penetrate to the ground. In other areas the
trees are further apart and sunlight can partially penetrate the tree canopy.
Tropical Rainforests
Rainforests cover 6% of the earth’s surface and are very important because they produce
oxygen as well as provide us with many products that are grown there, such as medicines,
rubber, coffee, fruit, nuts, oils and timber.
Coffee Plantation
Location of Tropical Rainforests
Tropical rainforests are found close to the equator (in the tropics) where it is hot all year
round with a very high rainfall. The largest tropical rainforests are located in the Amazon
basin (South America), the Congo basin, on the coast of Guinea (West Africa) as well as in
South East Asia. Smaller tropical rainforests are found in Central America, India,
Madagascar, Australia and the surrounding Pacific islands.
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Geography: Grade 6
Climate and Vegetation Regions of the World: Tropical Rainforests
The Amazon Rainforest (also known as the Amazon jungle) is the world’s largest tropical
rainforest and covers a land area of 7 million sq km. It is found mainly in Brazil, but with
significant areas in Peru and Colombia as well as smaller areas in Ecuador, Bolivia, Guyana,
Suriname and French Guiana.
The Amazon Rainforest accounts for more than 50% of the world’s remaining rainforest. It
has the greatest variety of plants and animals on Earth. One fifth of the world’s plants and
birds and one tenth of the world’s mammals, as well as over 2,5 million species of insects are
found here.
Amazon Rainforest
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Climate and Vegetation Regions of the World: Tropical Rainforests
The Congo Basin Rainforest is the second largest rainforest in the world and is located in
West Africa. It is famous for its gorillas, chimps and elephants.
The Guinea Rainforest is on the west coast of Africa and borders the Atlantic Ocean. It is
situated between Guinea Bissau and Sierra Leone. Over 100 endemic species (found nowhere
else in the world) are found here, but 40% are endangered as a result of poaching and habitat
destruction, caused by mining projects and agriculture.
Congo Basin Rainforest
Gorilla in Guinea Rainforest
Also in Africa is the Madagascan Rainforest. Around 90% of it has already been destroyed.
Around 75% of the species found here are endemic, such as species of lemurs and a primate
called the aye aye. There are over 1000 species of orchids found here, of which 85% are
endemic.
Madagascan Rainforest
The Central American Rainforest once covered the whole area. Large areas have now been
cleared for cattle ranching and sugar cane plantations. Many endemic animals and plants are
found here, including a variety of tropical birds.
Central American Rainforest –
Mangrove River, Mexico
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Climate and Vegetation Regions of the World: Tropical Rainforests
The South East Asian Rainforests cover an area from India and Burma in the west to
Malaysia in the east. They are the oldest rainforests in the world, thought to be 70 million
years old. Bangladesh has the largest area of mangrove forest in the world. Many critically
endangered plants and animals are found here, such as the two- horned Sumatran rhino and
the Malaysian tapir, of which there are thought to be only around 50 left in the wild.
South East Asia Rainforest –
Langkawi Island, Malaysia
The Australasian Rainforest is found in a small band on the North Queensland coast in
Australia. Rainforest once covered the entire continent. An amazing diversity of plants and
animals is found in this area.
Australasian Rainforest –
North Queensland, Australia
The Pacific Island Rainforests are found in the Pacific Islands, in places such as Hawaii,
Fiji, Tahiti and the Solomon Islands.
Pacific Island Rainforest – Kauai, Hawaii
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Rainforest Climate
Rainforests occur near the equator and for this reason the weather is always hot. They have a
tropical wet climate.
The temperature in a rainforest does not vary a lot from month to month.
It is usually around 34°C and does not fall much below 20°C. Humidity is
very high.
Because of the high temperatures, there is a lot of water evaporation, which
results in frequent rainfall. 50% of the rainfall in the rainforest is due to this
evaporation.
It rains for more than 90 days a year in the rainforest and the average annual
rainfall is around 200 cm and can exceed 1000 cm. A lot of this rain does not
reach the ground, but stays on the trees.
Mist After a
Heavy Rainfall
There are only two seasons in a rainforest, dry and wet. The dry season is very short.
The graphs below show the average temperatures and rainfall in Manaus, Brazil in the
Amazon Rainforest (03°06'S 01°00'W).
Maximum temperatures are between 30°C and 34°C throughout the year. The minimum
temperature does not vary a lot and is around 22°C.
Source: Hong Kong Observatory
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Climate and Vegetation Regions of the World: Tropical Rainforests
The rainfall graph for Manaus below shows that the highest rainfall occurs between January
and June, with June to October being drier months.
Source: Hong Kong Observatory
Rainforest Vegetation
Over 70% of the vegetation in the rainforest is trees. There are more types of trees in the
rainforest than in any other area of the world.
Most of the trees in tropical rainforests are broadleaf, evergreen trees.
Tropical Rainforest Plants
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Climate and Vegetation Regions of the World: Tropical Rainforests
Palms and tree ferns are also found in the rainforest.
Palms and Tree Fern Plants
The vegetation is so dense that not much light reaches the forest floor.
The types of plants found in rainforests vary depending on the location of the rainforest.
These plants are well adapted to the hot, wet climate, for example, with grooved leaves,
which do not break from the weight of the rain.
Trees of the same species do not usually grow together in the rainforest. This protects them
from disease and insect infestation.
The rainforest is often referred to as the ‘world’s largest pharmacy’ as there are many plants
that are found there which are used as medicines, for example, quinine which is used to treat
malaria and rosy periwinkle, which is used to treat leukemia.
There are four distinct layers of vegetation in the rainforest, as shown in the diagram and
described below.
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Climate and Vegetation Regions of the World: Tropical Rainforests
Forest Floor
This is the bottom layer of the rainforest, at ground level and is mostly in the shade. A lot of
vegetation falls to the forest floor and is broken down by decomposers such as termites and
earthworms, as well as heat and humidity.
There is not a lot of vegetation that can grow between the trees. Mainly ferns, moss and dead
leaves are found in this layer. The plants here are well adapted, for example with large leaves
to absorb as much sunlight as possible.
During heavy rains, the forest floor can flood.
Heavy Rains Cause Forest Floods
Understory/ Lower Canopy
This is the layer above the forest floor and where the trunks of trees of the
upper canopy, as well as smaller trees, plants and shrubs are found. There is
high humidity and shade in this layer.
Climbers called lianas are often found in this layer and climb up trees to get to
the sunlight.
Lianas Climbers
Upper Canopy
This is the next layer and is full of life. The canopy is typically
about 20 to 40 m high. There is more sunlight than the lower
levels. Many air plants, called epiphytes, such as the orchid,
grow here. Their roots do not touch the ground, so they live off
other plants, getting their nutrients and moisture from the air.
Epiphytic Aroid Grows on Tree Trunk
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Climate and Vegetation Regions of the World: Tropical Rainforests
Emergent Layer
This is the top layer and is above the upper canopy. Tall trees that need
a lot of sunlight grow here up to 40 m, above the forest, although some
can reach as high as 70 m. These trees often have shallow roots with
buttresses for extra support in the poor, wet soil. The leaves of these
trees are usually small and dark green to reduce water loss.
Rainforest Wildlife
Tall Rainforest Trees
There is a huge variety of animals that live in the rainforest,
especially insects. In fact, some species have not even been
identified yet! Half of the world’s species of animals and insects live here. The tropical
rainforests support one and a half million species of plants and animals.
Rainforest animals are well adapted to life in the trees, for example, by having a diet that
consists mainly of fruit.
Examples of wildlife found in the rainforest canopy include birds, insects, bats, squirrels and
monkeys.
A Toucan
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Tarsier Monkey
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Climate and Vegetation Regions of the World: Tropical Rainforests
In the understory of the rainforest, snakes, ocelots, tree frogs and birds such as guans are
found.
Boa Snake
Ocelot
Tree Frog
Black Throated – Piping Guan
Tapirs and other herbivores are found on the forest floor, and are hunted by jaguars and
snakes.
Tapir
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Jaguar
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Climate and Vegetation Regions of the World: Tropical Rainforests
Insects are the largest group of animals found in the rainforest. These include butterflies,
mosquitoes, stick insects and ants.
Butterfly
Wikimedia Creative Commons
Attribution Share-Alike: Muhammad Mahdi Karim
Stick Insect
Wikimedia Creative Commons
Attribution Share-Alike:
Fritz Geller-Grimm &FelixGrimm
Mosquito
Wikimedia Creative Commons
Attribution Share-Alike: Alvesgaspar
Deforestation
Deforestation is the permanent removal of a forest or woodland, for conversion to another
use, such as farmland or for urban development.
Logging of trees and clearing of the rainforest to make way for plantations, have endangered
the rain forest’s plant and animal life, as well as caused irreparable damage to the Earth’s
environment. Nearly 80,000 acres of rainforest are destroyed in this way, every day, causing
50,000 species to become extinct every year.
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Climate and Vegetation Regions of the World: Tropical Rainforests
Most deforestation these days occurs in tropical areas. Up to 90% of the rainforests in West
Africa have been lost due to deforestation.
Deforestation takes place for many reasons. Trees are cut down for timber (logging), to
supply wood for firewood, building materials and wood products such as furniture and paper.
Deforestation
Clearing Land for Agriculture
Other products that come from trees include: resins, waxes, fruits, nuts, berries and maple
syrup. A growing population has increased demand for these products.
The main reason for cutting down forests is for agricultural use. Subsistence farming
accounts for 48% of deforestation, commercial farming for 32%, whilst logging is 14% and
fuel wood removals, 5%.
Deforestation means permanent loss of potential life-saving medicines and has been found to
be a major cause of global warming. Trees and other plants remove carbon dioxide from the
atmosphere. When these trees are cut down, this carbon dioxide is released back into the
atmosphere (instead of being turned into oxygen by trees) and this accounts for
approximately 20% of the world’s greenhouse gas emissions.
Deforestation Causes Loss of
Life-Saving Medicines
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Climate and Vegetation Regions of the World: Tropical Rainforests
Trees and other plants remove carbon dioxide from the atmosphere. When these trees are cut
down, this carbon dioxide is released back into the atmosphere.
Go to the module on Deforestationin Save Your Planet, for more information:
http://www.mycyberwall.co.za/save-your-planet/resource-depletion/deforestation
People in the Rainforest
Although tropical rainforests have been home to indigenous people for centuries, relatively
few people live in rainforests because of the dense vegetation, which makes it difficult to
move about. The Mayans, Incas and Aztecs are well known indigenous people who lived in
the rainforests.
Indigenous groups live with nature and understand the importance of their environment.
They use plants for food as well as natural medicines.
The Yanomami people in South America live in the Amazon Rainforest. There are around
20,000 Yanomami people who live in groups of 50 to 400 people in around 200 villages.
They grow bananas, sugarcane, mangoes, sweet potatoes and papaya, as well as gather food
and hunt.
People of the Amazon Rainforest -The Yanomami People
Wikimedia Creative Commons
Attribution Share-Alike: Ambar
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Climate and Vegetation Regions of the World: Tropical Rainforests
Many tribes still live in the African rainforests. These include Pygmies who rarely grow taller
than 1,5 m. They are hunter-gatherers.
A Pygmy Tribe of Uganda
Attribution: Hector Cornesa/Shutterstock.com
African Pygmies
Wikimedia Creative Commons
Attribution Share- Alike: Keystone View Company
Other tribes living in the rainforests of Africa include the Aka in Central Africa and in
northern Congo, the Baka in south Cameroon and the Twa in central Zaire. These make up a
total of 150 000 forest dwellers in a large forest area, giving a very low population density.
DRC Aka Pygmy Family
Wikimedia Public Domain
Cameroon Baka Tribe
Wikimedia Public Domain
These days, people who live in the rainforest have displaced indigenous people, in order to
conduct activities such as mining and agriculture. Many indigenous people have also chosen
to join modern society.
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Climate and Vegetation Regions of the World: Tropical Rainforests
Temperate Rainforests
There is another type of rainforest, known as Temperate Rainforests that are found along the
Pacific Coast of USA and Canada, from California to Alaska, as well as in Tasmania, Chile,
the United Kingdom and Norway.
Tongass Rainforest - Alaska
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Wild Rivers National Park –
Tasmania, Australia
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