President Clinton said on Wednesday that he would permanently protect at least 40 million acres of Federal forest land from road building, logging and mining, using administrative actions meant to outmaneuver powerful opponents in Congress. Standing in front of a spectacular fall vista not far from the Shenandoah Valley -- and next to the grandson of Gifford Pinchot, who mapped out the first protected forests under Theodore Roosevelt -- Clinton said, "We're going to have a big fight on this for about a year." "In the end," he said later, "we're going to protect all this before it's too late."