F.3 Geog. notes/1.3 Why should we save the rainforests?/P.1 of 2
Pui Ying College
F.3 Geography
Section 1.3 Why should we save the rainforests ?
A.
Why are the rainforests important ?
1. Climatically, tropical rainforests help to moderate the world climate. The dense
forests take in carbon dioxide and gives off oxygen through photosynthesis. This
prevents the building-up of carbon dioxide in the atmosphere.
2. Ecologically, they are habitats for wildlife.
3. Culturally, they are homes for the native people.
4. Economically, they are sources of food, medicines and raw materials. There are
rich mineral resources, e.g. gold, in the rainforests. Trees in the rainforests also
provide valuable hardwoods, e.g. teak, which can be made into furniture.
5. Scientifically, lots of the species of the rainforests are unknown. They may be
sources of knowledge.
B.
What are the harmful effects of deforestation ?
I.
Atmosphere
1.
Micro-climate is created.
a.
Drier climate
If the trees are removed, there will be less evaporation and transpiration.
This results in less cloud and rain. So, the climate becomes drier.
b.
More extreme climate
As a result of reduced cloud cover and vegetation cover, there is loss of buffer.
Daily range of temperature becomes larger.
c.
More windy
Winds will be stronger because of reduced friction.
2.
Macro-climate is changed.
a.
Global warming
i)
Carbon dioxide (CO2) level increases due to reduced uptake of CO2 by the
reduced vegetation.
ii)
Since CO2 absorbs heat, the rise of CO2 level results in global warming.
iii) Global warming causes the melting of ice caps and so the rise of sea level.
iv)
So, the risk of flooding in coastal areas increases.
II. Lithosphere
1.
Soil erosion becomes more serious.
a.
After deforestation, there is less vegetation to absorb rainwater.
infiltration decreases and surface runoff increases.
So,
Soil is easily washed
away.
b.
Besides, there will be fewer plants’ roots to bind soil together.
c.
Furthermore, with the loss of protective vegetation cover, the topsoil is easily
eroded by wind and attacked by rain splash effect.
F.3 Geog. notes/1.3 Why should we save the rainforests?/P.2 of 2
2.
The nutrient cycle is broken.
a.
Dead leaves and branches decompose and return nutrients back to the soil.
b.
Without the rainforests, nutrients stored in plants are lost and the soil
becomes poor.
c.
This upset the ecological balance of the rainforest environment.
III. Hydrosphere
1.
Risk of flooding increases.
Deforestation causes the decrease of interception and infiltration while surface
runoff increases. Since soil erosion becomes more serious, silting results and risk
of flooding increases.
IV. Biosphere
1.
The food chain is broken.
As a result of reduced food supply and the destruction of their natural habitat, the
number and species of plants and animals are reduced.
2.
Secondary forest replaces primary forest.
After deforestation, secondary forest with shorter trees, fewer species diversity,
more open structure and lower density replaces the primary forest.
3.
Native people lose their home and traditional culture.
Vocabulary
1. moderate the world’s climate
11. macro-climate
21. nutrient cycle is broken
2. photosynthesis
12. global warming
22. decompose
3. habitats for wildlife
13. melting of ice caps
23. upset ecological balance
4. sources of raw materials
14. rise of sea level
24. hydrosphere
5. atmosphere
15. risk of flooding
25. reduced interception
6. micro-climate
16. lithosphere
26. silting
7. less evaporation
17. soil erosion
27. biosphere
8. less transpiration
18. reduced infiltration
28. food chain is broken
9. extreme climate
19. increased surface runoff
29. secondary forest
10. daily range of temperature
20. rain splash effect
30. traditional culture