With much of the rock climbing and mountaineering done above the tree line, the effort to protect alpine ecosystems is of paramount importance. Leave No Trace policies are strictly enforced and encouraged, such as camping only on bare rock, using only a camp stove, storing food safely where animals cannot get to it, and carrying out or properly burying human waste as necessary. Mountaineering in the North Cascades was first popularized by Fred Beckey; at age 15 he was the first to reach the summit of Sinister Peak in 1938, in 1939 he was the first atop Mount Despair, and the following year he was the first to climb Forbidden Peak. Beckey was the first to summit at least two dozen peaks in the North Cascades, and his exhaustive three-volume Cascade Alpine Guide books, first published in the early 1970s, have been called the Beckey Bible.