Causes and consequences of deforestation

1. What does this picture show?

2. Our learning objectives
Definition of deforestation
Causes and consequences of deforestation

3. Our learning outcome
At the end of the lesson you must be able to
Give the different causes of deforestation.
List the consequences of clearances of natural
vegetation.

4. Can you try to explain deforestation.

5. What is deforestation ?
• Deforestation refers to the loss or
destruction of naturally
occurring forests, primarily due
to human activities such as
logging, cutting trees for fuel,
slash-and-burn agriculture,
clearing land for livestock
grazing, mining operations, oil
extraction, dam building, and
urban sprawl or other types of
development and population
expansion.

6. What are the main causes
of deforestation ?
There are 5 main causes of
deforestation :
• Logging
• Industrialization
• Agriculture
• oil exploitation
• human disasters

7. How Fast is Deforestation
Happening?
• Currently, 12 million hectares of forests are
cleared annually.
• At this rate all moist tropical forest could be
lost by the year 2050, except for isolated
areas in Amazonia, the Zaire basin, as well as a
few protected areas within reserves and
parks.

8. Hots
• Do you think forests are important for the
environment.
• Trees too give out Carbon dioxide to the
atmosphere does this have a role in global
warming.

9. CONSEQUENCES OF DEFORESTATION
Alteration of local and global climates
through disruption of :
a) The carbon cycle. Forests act as a major carbon store
because carbon dioxide (CO2) is taken up from the
atmosphere and used to produce the carbohydrates,
fats, and proteins that make up the tree. When forests
are cleared, and the trees are either burnt or rot, this
carbon is released as CO2. This leads to an increase in
the atmospheric CO2 concentration. CO2 is the major
contributor to the greenhouse effect. It is estimated that
deforestation contributes one-third of all CO2 releases
caused by people.

10. • b) The water cycle. Trees draw ground water up
through their roots and release it into the atmosphere
(transpiration). In Amazonia over half of all the water
circulating through the region's ecosystem remains
within the plants. With removal of part of the forest,
the region cannot hold as much water. The effect of
this could be a drier climate.

11. Time to think critically
• How are plants able to keep the environment
cold?

12. Flooding
• Flooding. Deforestation can result to watersheds
that are no longer able to sustain and regulate
water flows from rivers and streams. Trees are
highly effective in absorbing water quantities,
keeping the amount of water in watersheds to a
manageable level. The forest also serves as a
cover against erosion. Once they are gone, too
much water can result to downstream flooding,
many of which have caused disasters in many
parts of the world

13. More effects ……
• Soil erosion With the loss of a protective
cover of vegetation more soil is lost.
• Silting of water courses, lakes and dams
This occurs as a result of soil erosion.
• Extinction of species which depend on the
forest for survival. Forests contain more
than half of all species on our planet - as the
habitat of these species is destroyed, so the
number of species declines
• Desertification The causes of desertification
are complex, but deforestation is one of the
contributing factors .

14. Summary
• Define deforestation
• List four causes of deforestation
• Give three effects of deforestation on the
environment.