> Yes, we still have a lot of trees. But more than two or three centruries ago? I don't think so. It was once said that a squirrel could go tree to tree from the east coast to the Mississippi without putting his foot on the ground.

Said by whom, when? I'm not convinced this is true. The Indians, contrary to what one might think, cut down a great many trees themselves. (Depending on the tribe, of course; there were hundreds of tribes, and their cultures were varied and divergent from each other. Some worshipped trees and nature, but not all.)

Today, trees are cut down, and trees are grown. In the United States, I believe forests are growing back at least as fast as we're harvesting the wood in them. It's not like there's actually a whole huge amount of indiscriminate tree cutting going on without trees being planted and grown to replace them. A lot of the wood that's harvested here is selective cutting anyway, not clear cutting, which is a good thing, as instead of all the trees in a young forest suffering in their fight for sunlight, some are harvested for wood and those remaining are freed from constriction and enabled to grow stronger and become healthier.