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Topic 6: The issue of global
warming
Just plant more trees????
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2. Topic 6: The issue of global
warming
6.1.5: Management strategies to address global
warming
Can't we just plant more trees?
The media often present planting more trees as a possible
solution to global warming.
While trees, just as like
every plant, do absorb
carbon dioxide from the
atmosphere and sequestrate
(convert) it into plant tissue.
Can they provide a real
cebitz.
answer?
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3. Topic 6: The issue of global
warming
6.1.5: Management strategies to address global
warming
Can't we just plant more trees?
CO The theory
During photosynthesis plants absorb
CO2 from the atmosphere which
combines with water and minerals
from the soil to make new plant
material as the plant grows.
HO Trees being big plants absorb lots of
cebitz.
CO2 as they grow (carbon fixation)
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4. Topic 6: The issue of global
warming
6.1.5: Management strategies to address global
warming
How much carbon do trees fix?
Age of trees Carbon fixed each year Cumulative amount of carbon fixed
(years) (t C ha-1 year-1) (t C ha-1)
5 0.2 0.2
10 7.0 21.0
15 14.0 77.0
20 21.0 167.8
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Based on an idea from: Problem Solving in Environmental Biology; A.R Ennos and S.E.R Bailey; 1995 Longman Science

5. Topic 6: The issue of global
warming
6.1.5: Management strategies to address global
warming
How much carbon do trees fix?
Carbon fixation by Pine trees
Cumulative amount of carbon fixed (t C / ha
200 When tree saplings are very young
the rate of respiration is almost
150
equal to photosynthesis so the
100 amount of carbon fixed is negligible.
50 From around year 5 the rate of
photosynthesis exceeds respiration.
0
0 5 10 15 20
cebitz. Tree age (years)
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Based on an idea from: Problem Solving in Environmental Biology; A.R Ennos and S.E.R Bailey; 1995 Longman Science

6. Topic 6: The issue of global
warming
6.1.5: Management strategies to address global
warming
So what does that mean?
Imagine an average European engineering factory
producing around 200 t C year -1
This would mean that if you planted trees today, in 20
Certainly not an years (how long it takes the tress to grow) the factory
average factory
would produce 200 x 20 = 4000 t C
If 1 ha of trees absorbs 167.8 t C in 20 years then you
would need 4000/167.8 = 23.8 ha of trees just to absorb
cebitz. the carbon from one small factory
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Based on an idea from: Problem Solving in Environmental Biology; A.R Ennos and S.E.R Bailey; 1995 Longman Science

7. Topic 6: The issue of global
warming
6.1.5: Management strategies to address global
warming
Can't we just plant more trees?
The Conclusion - NO
Actually planting trees to offset the carbon footprint of the
developed world would need many millions of hectares of available
land.
Reforestation is more important for preserving and restoring
habitats than it is for reducing the effects of increased CO2
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Based on an idea from: Problem Solving in Environmental Biology; A.R Ennos and S.E.R Bailey; 1995 Longman Science