Yosemite National Park a larger national park by 1890, one which encompassed the valley and its surrounding mountains and forests, paving the way for the National Park System. Yosemite is one of the largest and least fragmented habitat blocks in the Sierra Nevada, and the park supports a diversity of plants and animals. The park has an elevation range from and contains five major vegetation zones: chaparral and oak woodland, lower montane forest, upper montane forest, subalpine zone, and alpine. Of California's 7,000 plant species, about 50% occur in the Sierra Nevada and more than 20% are within Yosemite. The park contains suitable
Yosemite National Park thawing of the Ice Age (such as the Little Ice Age). Climate change has reduced the number and size of glaciers around the world. Many Yosemite glaciers, including Merced Glacier, which was discovered by John Muir in 1871 and bolstered his glacial origins theory of the Yosemite area, have disappeared and most of the others have lost up to 75% of their surface area. Yosemite has a Mediterranean climate (Köppen climate classification "Csa"), meaning most precipitation falls during the mild winter, and the other seasons are nearly dry (less than 3% of precipitation falls during the long, hot summers). Because