This article is about the human impact on the environment. For a description of natural features, see Ecology of California.
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California's Mediterranean climate makes vegetation susceptible to wildfires through the dry summers. Aboriginal Californians used fire to control brush, promote growth of seed-producing plants important to subsistence, and perhaps as an aid to hunting wildlife. These periodic fires kept woodland areas relatively open until 20th century laws curtailed burning in an effort to protect structures.[1]European crops and livestock were introduced with missions along the coast from San Diego to San Francisco Bay through the late 18th and early 19th century. The California Gold Rush caused explosive population growth making San Francisco the only 19th century city west of St. Louis, Missouri.[2] Water soon became the limiting factor for population growth, and early laws established water rights for irrigation and hydraulic mining. The Great Flood of 1862 washed gravel displaced by gold mining downstream to cover riparian cropland and fill formerly navigable stream channels serving as transportation corridors to San Francisco Bay. The damage encouraged passage of water pollution control legislation, broadly regulating disposal of waste to include relatively innocuous materials like gravel.[3] These California laws provided a template for the United States Environmental Protection AgencyNational Pollutant Discharge Elimination System.
California's aboriginal population of about 300,000 was distributed in relatively self-sufficient groups with subsistence resources on the coastal wetlands near the mouth of the Smith River, along the Klamath River and its interior wetlands, on the coastal wetlands surrounding Humboldt Bay, on the wetlands surrounding San Francisco Bay and the rivers of the California Central Valley, along the Salinas River, and along the coastal wetlands between Morro Bay and San Diego Bay. Early European trade was by ship, but El Camino Real extended northward along the southern California coast and through the California Coast Ranges from Mexico to San Francisco Bay to link individual missions with seaports. San Francisco Bay became the most important seaport for the gold rush and ferries of San Francisco Bay carried trade between the seaport and mining areas. The California Trail became the first important land link between San Francisco Bay and the eastern United States during the gold rush and became the route of the First transcontinental railroad in 1869. The gold rush brought approximately 200,000 new residents to California, and 36% of Californians lived around San Francisco Bay by 1870.[2] Lumber from coastal redwood forests was transported to San Francisco by ships. Redwood proved poorly suited for railroad ties, so fast-growing Australianeucalypts were widely planted to provide future supplies.
Unsuccessful gold prospectors soon recognized California's agricultural potential and their mining equipment began adjusting timing and location of stream flows to increase food production. Mono Lake and Tulare Lake shrank as flows were diverted to irrigation.[7] Little Lake was drained to form the town of Willits, California in 1874,[8] and Laguna de Santa Rosa was drained to bring rail service to Sonoma County.[9] The Klamath Project drained large shallow lakes for conversion to cropland in 1905. The Potter Valley Project diverted water from the Eel River to the Russian River in 1906 to provide hydroelectric power to Ukiah, California; and Lake Pillsbury was formed behind Scott Dam in 1922 to increase summer flows allowing irrigation of Potter Valley.[10]
Aside from simple agricultural environments, water transfer has created a unique southern California urban area. The relatively low urban population density encouraged by automobile mobility features edge effect habitats including a broad range of landscaping plants. Omnivores able to cross streets, roads, and freeways thrive in this spatially fragmented habitat with dry season water available from landscape irrigation. Columbidae, Corvidae, house sparrow, European starling and gulls fly between isolated habitat segments, while raccoons, opossums, skunks and rats travel under bridges and through culverts and storm drains. Animals killed during unsuccessful crossing attempts are a food source for scavengers also seeking garbage or food intended for pets or wild birds and squirrels. Domestic cats and dogs kill small animals for recreation and have established feral predator populations. Coyotes prey on these smaller predators.[13]
^Wilder, Robert J. Listening to the sea: the politics of improving environmental protection (1998) University of Pittsburgh Press ISBN0-8229-5663-2 p.30|pages
^Durham, David L. California's Geographic Names: A Gazetteer of Historic and Modern Names of the State (1998) Quill Driver Books ISBN978-1-884995-14-9 p.168