In this June 19, 2012 photo provided by the Colorado National Guard, an aircraft drops a load of fire retardant slurry above the High Park wildfire about 15 miles west of Fort Collins, Colo. The ammonium phosphate dropped from airplanes to slow the spread of raging wildfires can turn a pristine mountain stream into a death zone for trout and some say the retardant has never been proven effective. (AP Photo/Colorado National Guard, John Rohrer)