#11 - Logging industry official: Harvesting trees from

[Administrator]

Complete Question Explanation

Weaken. The correct answer choice is (B)

The official states that when trees decompose, they release carbon dioxide. He also explains that rapidly-growing younger trees absorb more carbon dioxide than do older trees. On that basis, he concludes that logging for manufacture would reduce carbon dioxide levels in the atmosphere.

While you may legitimately propose that the argument makes other assumptions, at the most essential level the reasoning implies that the official assumes that the younger trees will be able absorb more than the logged trees release.

That is important, because a logged tree may decompose and quickly release the carbon dioxide it has accumulated over many years, thus making a higher yearly absorption rate fairly insignificant in the face of such a glut of carbon dioxide. Since you are asked to weaken the stimulus, you should focus on that possibility.

Answer choice (A): Since the argument merely concerns carbon dioxide levels, responses about whether animals will die are wholly irrelevant.

Answer choice (B): This is the correct answer choice. If much of the organic matter from old-growth trees is made into products that decompose rapidly, that offers reason to believe that much of the accumulated carbon dioxide from an older tree will be rapidly released, which challenges the idea that a younger tree’s absorption rate will be able to counter the glut of carbon dioxide that has been quickly released.

Answer choice (C): From the stimulus, one would expect a younger tree to have much less stored carbon dioxide. The stimulus was based, however, on what the young trees will absorb if they are able to grow, not on what they have stored, so this choice is wrong. Remember, the stimulus did not directly concern whether it is better to harvest older trees than it is to harvest younger trees.

Answer choice (D): This choice does not weaken the argument, because it merely observes that debris in the forest decomposes and releases carbon dioxide. That basically is a restatement of the stimulus, which points out that when large trees decompose they release stored carbon dioxide. You need to show why that consideration might not lead to the conclusion that it is better to log old trees than to let them eventually die.

Answer choice (E): This choice suggests that it can take newly planted trees many years to reach the size of older trees. However, that does not challenge the idea that the younger trees will grow rapidly and absorb more carbon dioxide. Some trees are large, so a newly planted tree could grow rapidly but still take a long time to reach the size of an old-growth tree. The stimulus states that rapidly-growing trees absorb more carbon dioxide, so the idea that trees might grow rapidly, or have rapid-growth phases, for a long time before reaching the size of old-growth trees strengthens rather than weakens the stimulus.

[lawschoolforme]

Hello,

I understand why B is right, but not why C is wrong. Doesn't C weaken the official's statement by showing how "making room for rapidly growing young trees" isn't going to absorb more carbon dioxide from the atmosphere?

Thanks!

-lawschoolforme

[David Boyle]

Hello,

I understand why B is right, but not why C is wrong. Doesn't C weaken the official's statement by showing how "making room for rapidly growing young trees" isn't going to absorb more carbon dioxide from the atmosphere?

Thanks!

-lawschoolforme

Hello lawschoolforme,

Since C says "A young tree contains less than half the amount of carbon dioxide that is stored in an old tree of the same species", that would seen to strengthen the argument if anything, because if they don't have a lot of carbon dioxide in them, it seems they are pretty "clean", and can also absorb a lot of carbon dioxide maybe.

Hope that helps,
David

[andriana.caban]

Intuitively, I knew (B) was correct. However, because I assumed "organic matter" meant that the carbon dioxide couldn't be transferred into products I convinced myself it was incorrect. I thought that once these old-growth trees were harvested carbon dioxide would be released into the air (how can these trees be harvested, then created into products that contain the carbon monoxide into the tree?). On this assumption I chose (C), understanding (C) to mean the following:

If young trees have 1/2 less than old trees, this could mean that they are absorbing more carbon dioxide but not actually retaining anything. So, clearing out old trees isn't necessarily the most beneficial. Young trees cannot retain the carbon dioxide it absorbs until it grows. Harvesting old trees in order to allow young tress to grow won't work, because carbon dioxide will still be released into the atmosphere if it is harvested (since young trees can't retain carbon monoxide)

Please let me know what was wrong with my assumption for (B) and reasoning for (C), thanks!

[Adam Tyson]

The idea offered in the stimulus is that harvesting the old trees will prevent them from decomposing when they die. When they decompose, they release CO2, so if we can prevent decomposition, we can prevent that release, basically trapping the CO2 in whatever we make from the harvested tree - tables, chairs, flooring, etc.

Young trees having less CO2 in them than older trees doesn't do anything to change that equation. As long as we are preventing the release of CO2 from the old trees, the theory is that we should be reducing the CO2 in the atmosphere. And the young trees might not have as much CO2 in them as they will when they are older, but that's kind of the point - they will continue to absorb CO2 as they age! They just haven't gotten fully saturated yet. The issue isn't how much they are currently holding, but how much they will absorb over the course of their lives. Think of them as sponges, slowly absorbing water over time - it's not how wet they are right now, but how wet they will become, that matters.

[Coleman]

I'd like to be more specific about the setting drawn in the passage.

Does this passage imply whether there will be a particular process to separate trees that are usable for manufacture, or otherwise will be left out in the forest? because it sounded more like, the industry will harvest ALL the old trees from old-growth forests regardless of their usefulness in order to avoid "large old trees die in the forest and end up releasing their stored carbon dioxide."

Do old-growth trees in answer choice B necessarily indicate only those trees abandoned in the original forests because they are unusable as lumber?

[ibarrajo]

Hi All,

Thanks for your explanation, Adam. However, I’m not entirely sure how you got to that conclusion “the idea offered in the stimulus is that harvesting the old trees will prevent them from decomposing when they die.” I suspect it might come from the premise “when large old trees die in the forest, they decompose” which, by contrast, could imply that when old trees are taken out of the forest/harvested for manufacture, the resulting products would no longer decompose (thus releasing C02) when they reach old age/“die”?

Even if this was the case, and we accept this to be the better interpretation of the premises than those offered throughout the thread, how does (B) weaken the idea that young trees will reduce the C02 in the atmosphere?

(B) says “Much of the organic matter from old-growth trees, unusable as lumber, is made into products that decompose rapidly”

From this, I don’t get the sense that younger trees will not be able to absorb the C02 released from the decomposed products. In fact, we know they absorb C02 at a faster rate (or just “more’) than the older trees do. So, couldn’t It be argued that this answer doesn’t really weaken the conclusion and that we don’t know whether the younger trees will not be able to absorb the released CO2 in time? Also, the vague sense of time here makes it challenging to fully grasp the nuances in the argument. That is, I’m not sure what “rapidly” means in terms of the yearly C02 absorption rate? Do decomposing products rapidly mean a year or more? If “rapidly” is interpreted as more than a year, then the argument that C02 is reduced by the young trees still remains.

Any insight is much appreciated!

________________________________________

The idea offered in the stimulus is that harvesting the old trees will prevent them from decomposing when they die. When they decompose, they release CO2, so if we can prevent decomposition, we can prevent that release, basically trapping the CO2 in whatever we make from the harvested tree - tables, chairs, flooring, etc.

Young trees having less CO2 in them than older trees doesn't do anything to change that equation. As long as we are preventing the release of CO2 from the old trees, the theory is that we should be reducing the CO2 in the atmosphere. And the young trees might not have as much CO2 in them as they will when they are older, but that's kind of the point - they will continue to absorb CO2 as they age! They just haven't gotten fully saturated yet. The issue isn't how much they are currently holding, but how much they will absorb over the course of their lives. Think of them as sponges, slowly absorbing water over time - it's not how wet they are right now, but how wet they will become, that matters.

[Paul Marsh]

Hi ibarrajo!

we don’t know whether the younger trees will not be able to absorb the released CO2 in time

This is exactly correct, and tells us why (B) is the correct answer. (B) tells us that the harvesting of old-growth trees results in much of its organic matter decomposing more quickly by being integrated into certain products. This creates a scenario where we are unsure whether the presence of younger trees will be enough to offset the increased rapidity of the CO2 transmissions of the decomposing old-growth trees; that is enough to make the answer correct. A good Weaken answer choice does not have to destroy the conclusion beyond any doubt; it just has to cast some doubt upon how a conclusion is drawn from its premises. Typically it will weaken the connection between premise and conclusion. As you yourself mentioned, (B) does that by leaving us in doubt about whether harvesting the old trees will in fact decrease CO2 emissions. This makes it a good answer.

Hope that helps!