Logical Reasoning

PT11 · S4 · Q11 Logging industry official: Harvesting trees

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Logging industry official: Harvesting trees from old-growth forests for use in manufacture can reduce the amount of carbon dioxide in the atmosphere, since when large old trees die in the forest they decompose, releasing their stored carbon dioxide.

Conclusion

Harvesting trees from old-growth forests can reduce the amount of carbon dioxide in the atmosphere.

Evidence (since, moreover)

When large old trees die in the forest, they decompose, releasing their stored carbon dioxide.

Harvesting would make room for rapidly growing young trees, which absorb more carbon dioxide than do trees in old-growth forests.

Evaluate

This has the ingredients of a Plan/Goal type argument.

GOAL: reduce CO2 in the atmosphere PLAN: harvest trees from old-growth forests

To be skeptical, we want to think, Maybe the amount of CO2 that large old trees suck up while they're alive is greater than the CO2 they emit when they ultimately die. Maybe the process of planting rapidly growing trees involves emitting a lot of CO2.

Goal

We need a way to argue that if we cut down these large old trees, we won't actually reduce the CO2 in the atmosphere.

11.

Which one of the following, if true, most seriously weakens the official’s argument?

Many old-growth forests are the
Unclear Impact
If we cut down the old growth trees and then it leads to thousands of animals being endangered, does that reduce CO2? Add CO2? We don't know what effect, if any, the disappearance of these animal species would have on CO2.
6% picked this
Correct
Much of the organic matter
Why this is right
We cut down these old-growth trees, and much of their matter is made into products that decompose rapidly, so they're still emitting CO2 into the atmosphere. The whole idea of cutting them down was to prevent them from decomposing on the forest floor when they die. But this answer is saying they're going to end up decomposing either way, so we won't really be preventing CO2 emissions. Granted, we might argue that SOME of the old-growth tree can still be used as lumber and might not decompose, but we also have to balance that against the fact that if the trees were still alive in the ground, they would be removing CO2 the way all plants do through photosynthesis.
Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.
48% picked this
A young tree contains less
Irrelevant Comparison
We're not surprised to hear that young trees (which are much smaller) have a smaller tank of absorbed CO2. The benefit of young trees was not supposed to be that they currently have more CO2 stored in them, it's that they suck in CO2 from the atmosphere at a faster rate than old trees do.
23% picked this
Much of the carbon dioxide
No Impact
This is a factor that is true whether or not we cut down the old-growth trees. It doesn't give us anyway to compare the world where we leave them to the world where we harvest them.
13% picked this
It can take many years
No Impact
It doesn't matter that it takes a long time for young trees to grow to the size of old trees. The key point the author cared about is that while they're growing, young trees are sucking up more CO2 than old trees are, on a daily basis.
10% picked this

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