thevenus -
Certainly everyone is entitled to his view. However, I have discussed this question with literally hundreds of students and none has expressed the opinion that this is "crap."
If you look to the postings above yours you will see that the others who have posted - a couple of dozen people - have liked the question or the explanation or both.
What you will want to do in the future is to look at each question as a learning opportunity. In this case I can see where you can alter your approach in order to be more successful at critical reasoning.
You say
Secondly, virtually the atmosphere of two places can be similar but this is not strong enough to say that the consequences or the agriculture would be the same.
None of the answer choice is good enough !
You have a mistaken impression of what it means to strengthen an argument. You do not need for the correct answer to make the conclusion absolutely guaranteed, all you need to do is to make the conclusion a little, or a lot, more likely.
Let me give you an analogy in math that might help. A strengthen question would look like this in math "2 + x = 4." Your conclusion is 4, the current premise is 2 and the answer choice will replace x. What you seem to be looking for is a "2" so that you can say "2 + 2 = 4." That would guarantee the conclusion. What the GMAT is more likely to give is "x is a positive integer."
Now we can say "2 + a positive integer = 4." Now the conclusion is a little more likely because after all the number 2 (which we need to make our conclusion true) is a positive integer. So now our conclusion is that much closer.
The same thing applies to this argument. It is basically the transitive property... "harvesting peat in Ireland has not contaminated the water supply + this country's wetlands are virtually identical to those in Ireland = this country can safely harvest peat"
Now the conclusion is not guaranteed of course because the harvesting done in this country might be done in a very bad way and cause harm that did not occur in Ireland. But we do not need to make the conclusion true only to increase the likelihood that it is true.
I hope this helps you.