 More recently , preservationists persuaded Congress to designate 677 @,@ 600 acres ( 274 @,@ 200 ha ) , or about 89 % of the park , as the Yosemite Wilderness — a highly protected wilderness area . The Park Service has reduced artificial inducements to visit the park , such as the Firefall , in which red @-@ hot embers were pushed off a cliff near Glacier Point at night . Traffic congestion in Yosemite Valley during the summer months has become a concern . Two electric buses commenced service in September 1995 . The buses are quiet and do not emit pollutants . Eventually , all the buses in Yosemite will be electric . The 1996 Yosemite Valley Landslide killed a hiker and the January 1997 Merced River flood damaged many roads and several campgrounds . 
