are tropical rainforests found?
rainforests are located around the equator where temperatures
stay near 80 degrees year round. Rainforests receive 160 to 400
inches (400-1000 cm) of rain each year. The largest rainforests
are in Brazil (South America), Zaire (Africa) and Indonesia (South
East Asia). Other tropical rainforest places are in Hawaii and
the islands of the Pacific & Caribbean.
is the tropical rainforest?
Tropical Rainforest is a forest occurring in tropical areas of
heavy rainfall. It is abundant with many species of wildlife and
vegetation. Rainforests cover less than two percent of the Earth's
surface. They are home to some 50 to 70 percent of all life forms
on our planet. Rainforests are the most productive and most complex
ecosystems on Earth.
is the structure of vegetation in the rainforest?
The image above shows a typical cross section in the rainforest.
are the tallest trees and are usually over 50 metres tall. The
Kapok tree is an example of an emergent.
The sea of
leaves blocking out the sun from the lower layers is called the
canopy. The canopy contains over 50% of the rainforest
wildlife. This includes birds, snakes and monkeys. Lianas (vines)
climb to the canopy to reach this sun light.
canopy mainly contains bare tree trunks and lianas.
layer has the densest plant growth. It contains shrubs and
ferns and other plants needing less light. Saplings of emergents
and canopy trees can also be found here.
floor is usually dark and damp. It contains a layer of rotting
leaves and dead animals called litter. This decomposes rapidly
(within 6 weeks) to form a thin humus, rich in nutrients.
did the tropical rainforest get like this?
high rainfall and year-round high temperatures are ideal conditions
for vegetation growth. The wide range of plants encourage a huge
variety of insects, birds and animals.
is the impact of humans on the tropical rainforest?
Deforestation (cutting down trees) is a major problem caused by
humans in the tropical rainforest. Global
Rates of Deforestation:
acres (1 hectare) per second: equivalent to two U.S. football
acres (60 hectares) per minute
acres (86,000 hectares) per day: an area larger than New York
million acres (31 million hectares) per year: an area larger
The image below shows some of the causes and effects of deforestation
in the Amazon Rainforest. Place you mouse over the image to disover
these causes and effects. Click to view infomation on each factor.
Most clearances are still by the local people and tribes needing
land on which to grow crops. They clear the forest by ‘slash and
burn’. Vegetation is cut down and then burned. The ash acts like
a fertiliser adder nutrients to the soil. When the soil begins
to turn infertile (usually after 3-5 years) the people move on.
This is called shifting cultivation. It is a sustainable method
of farming in the rainforest. It ensures the forest will recover.
Commercial logging is the major cause of primary rainforest destruction
in South East Asia and Africa. World wide, it is responsible for
the destruction of 5 million ha. per year. Logging roads enable
landless people to enter the forest. In Africa, 75% of land being
cleared by peasant farmers is land that has been previously logged.
Ranching is a major cause of deforestation, particularly in Central
and South America. In Central America, two-thirds of lowland tropical
forests have been turned into pasture since 1950.
An unlimited supply of water and ideal river conditions have led
to the development of hydro electric power stations (HEP Stations).
There are nearly 3 million landless people in Brazil alone. The
government has cleared large areas of the Amazon Rainforest and
encouraged people to move there. The scheme has not been successful.
Farmers stay on the same land and attempt to farm the land year
after year. Nutrients in the soil are quickly exhausted as there
is no longer a humus layer to provide nutrients. The soil becomes
infertile and nothing will grow.
The mining of iron ore, bauxite , gold, oil and other minerals
have benefited many LEDCs. However, it has also devastated large
areas of rainforest e.g. The Amazon.
is causing many problems at a range of scales:
- About 80% of the rainforests
nutrients comes from trees and plants. That leaves 20% of the
nutrients in the soil. The nutrients from the leaves that fall
are instantly recycled back up into the plants and trees. When
a rainforest is clear-cut, conditions change very quickly. The
soil dries up in the sun. When it rains, it washes the soil
away. The rainforest never fully recovers. Wildlife and plant
life is reduced.
- Elimination of Indian groups
and their way of life
- Estimates suggest that 80%
of forest Indians have died since the arrival of Europeans in
the sixteenth century. Most have died from western diseases
such as malaria to which they have no immunity. Those remaining
have been forced away by the construction of roads, ranches,
mines and reservoirs
- When vegetation
is removed soil is left exposed to the heavy equatorial rainfall.
It is rapidly eroded. The removal of top soil means little vegetation
will grow. Also, soil erosion leads to flooding as soil is deposited
on river beds.
Rainforest canopies absorb carbon dioxide which is a gas in the
atmosphere. When the rainforests are burned and cleared, the carbon
is released. Also, when trees are cut down they can no longer
absorb carbon dioxide. This means more carbon dioxide is in the
atmosphere. Carbon dioxide allows heat through the atmosphere
(suns rays). However, it will not allow reflected energy to escape
from the atmosphere. This is called the greenhouse effect and
causes global warming.
is the future for the tropical rainforest? - Sustainable Development
development in the rainforest is to be sustainable (e.g. although
the resources are used to aid development, it/they will still
exist for future generations to use) a number of measures must
be taken. These include:
- Trees should be replanted in areas of deforestation.
Cultivation - Farmers should move on after 2-3 years to allow
the rainforest to recover.
tapping - More sustainable methods of exploiting the rainforest
should be pursued e.g. rubber tapping
trees - Trees should only be cut down when they reach a certain
size. This will ensure younger trees survive longer and will encourage
careful management of the rainforest.