While I have never actually hugged a tree, I have sat under many and leaned back against them. And I do have an abiding interest in Nature and the part we play in it. Everyone should. One of our most noticeable effects on our surroundings is pollution—ground, air, and water.
Since three/fourths of our planet is water, we tend to think the supply is inexhaustible. It isn't. Essentially, we have all the water we're ever going to get, and have had since the Earth reached something resembling its current form. Water doesn't replenish, it recycles.
If we pollute our water, it stays that way unless we take out the pollution. And where do we put the pollutants? If we dump them in a landfill, they wind up right back in the water supply. The easiest and less costly way to avoid pollution is: not pollute in the first place. Try telling that to industries that don't seem to care about pollution as long as it's profitable. But don't blame just industry—agriculture and urban run-off pollute far more.