 One species of interest is the limestone salamander , an extremely rare amphibian whose only habitat is in the Merced Canyon downstream of Yosemite Valley . The limestone salamander depends on the granite walls of the Merced Canyon to survive . To protect the species , a 20 @-@ mile ( 32 km ) segment of the canyon covering 1 @,@ 600 acres ( 6 @.@ 5 km2 ) was designated in 1986 an " Area of Critical Environmental Concern " . 
