Somebody made a recent emotional appeal yesterday on facebook with pictures of national monuments and parks stating that “would you like a pipeline covering this ground? I am wondering, isn’t that wrong? Aren’t the pipelines underground? Wouldn’t it take an earthquake to break one?
I am not entirely sure about plants, I think that even plants have limits of efficiency, although that is certainly a higher concentration than what we generally get from the air we breathe.
I would expect some pipelines to be underground and some to be above ground, but I really do not know.
I think it unlikely that pipeline companies would choose to put pipelines above ground at parks or monuments. Besides, pipeline companies require permission to place pipelines on (or under) ground that they do not own.
From what I’ve read, plants would do better with a higher concentration of CO2.