one simple concept...the "carrying capacity" of the land under given conditions. They learned it the hard way on Easter Island, and they are learning it in Ethiopia and other places today. If we abuse the land (OR the sea!)and reduce its capacity to feed us, we must reduce our own population. The mathematics is inexorable: if there is not enough, people will suffer and/or die...if we are smart enough to be ABLE to affect out own environment in extreme ways, we are smart enough to figure out how to preserve it. It just involves looking past next week....