Fouling Our Own Nest By BOB HERBERT Do you remember the character Pig-Pen in the "Peanuts" cartoons? He was always covered with dirt and grime. He was cute, but he was a walking sludge heap, filthy and proud of it. He once told Charlie Brown, "I have affixed to me the dirt and dust of countless ages. Who am I to disturb history?" For me, Pig-Pen's attitude embodies President Bush's approach to the environment. We've been trashing, soiling, even destroying the wonders of nature for countless ages. Why stop now? Who is Mr. Bush to step in and curb this...