Yosemite National Park is causing the problem. Despite the richness of high-quality habitats in Yosemite, the brown bear, California condor, and least Bell's vireo have become extinct in the park within historical time, and another 37 species currently have special status under either California or federal endangered species legislation. The most serious current threats to Yosemite's wildlife and the ecosystems they occupy include loss of a natural fire regime, exotic species, air pollution, habitat fragmentation, and climate change. On a more local basis, factors such as road kills and the availability of human food have affected some wildlife species. Yosemite National Park has
Yosemite Valley Bridges Yosemite Valley Bridges The Yosemite Valley Bridges are eight bridges in the Yosemite Valley of Yosemite National Park, most of them spanning the Merced River. Five of them were built in 1928, with the remainder built between 1921 and 1933. The bridges feature a concrete structure faced with local stone, in an elliptical or three-centered arch configuration. They are notable for their uniform character and for their conformance to tenets of the National Park Service rustic style. Design work for the seven newer bridges was by George D. Whittle of the San Francisco District Office of the U.S. Bureau of