Chapter 2: The Nonhuman World

The Nonhuman World
What largely defines San Francisco are its nonhuman, or physical attributes. The city is enclosed by three bodies of water, the San Francisco Bay, the Pacific Ocean, and the Golden Gate Strait, and the cool waters moderate the climate. The San Francisco Bay was previously one of California's valleys, "...but the estuary has been inundated with saltwater multiple times in the past fifteen million years, until the present shallow bay was created ten thousand years ago." (Mayda, 507).

San Francisco's Watersheds

(museumca.org)

(toxics.usgs.gov)

San Francisco's climate is described best by Alexander McAdie's statement, "On the coast of California there is a city justly famed for the abnormalities of its climate. Overcoats and heavy wraps are worn in midsummer, while the lilies bloom in December."The city is located in the Northwestern climate region and "The westerly winds of the marine west coast bring moisture from the Pacific Ocean..." (37, Mayda) What causes the frequent fog is the encounter of continental and oceanic air masses."Hot temperatures inland create a low pressure zone over Northern California's Central Valley. Since hot air rises, heavier cold air rushes in through a break in the mountains that is the Golden Gate passage from ocean to bay. The flow from the high to low pressure zones pulls the fog through the passage." (www.examiner.com) The city is appropriately known as the "air-conditioned city", because the fog naturally purifies the air.

Due to the San Francisco Bay estuary's cooling effects, the temperature is mainly mild, with coastal stratus fog during the summer, and radiation fog during the winter. "In addition to the normal cool temperatures of the mid-latitude Pacific Ocean, the water temperatures are modified by the upwelling of cold water along the California coast."(http://ggweather.com/sf/narrative.html)

Summer Fog (http://blog.sfgate.com)

During the summer, the average maximum temperatures are between 60 degrees F and 70 degrees F, and the minimum temperatures are between 50 degrees F and 55 degrees F. In winter, the highs are between 55 degrees F and 60 degrees F and the lows are within in the 45 degrees F to 50 degrees F. The wind, which is conducted by the diverse terrain, creates many microclimates, with the warmest temperatures being found farthest from the coast, particularly areas separated from the coast by mountains or hills, and in valleys. Near the Pacific coast, summers are cool and foggy and winters are mild and rainy.

"Winter Fog" (RobertCambellPhotography.com)

According to the U.S. Department of Agriculture's Reconnoissance Soil Survey of the San Francisco Bay Region California, "The year is divided into a wet and dry season, which coincide with winter and summer."(http://soils.usda.gov/survey)  The soil on the coast and on the Western slopes of Berkley Hills is least suited for agriculture, as the climate is too cold and moist. The Agricultural Production Within the San Francisco Foodshed study states that: "Most agricultural production by value and volume comes, not from the immediate Bay Area, but from the fertile valleys beyond the hills surrounding San Francisco and its neighboring communities." (http://www.farmland.org)
San Francisco's soil is of the pedocal type. "Pedocal soils are quite fertile because precipitation rarely reaches the water table and soil nutrients are recycled, but the lack of water limits agricultural productivity." (39, Mayda)

According to the aforementioned source, the vegetation type is boreal forest, but the area also boasts a rich array of terrestrial and aquatic ecosystems; "The region’s spectacular array of land-based habitats ranges from shady forests and lush, tree-lined riparian zones to arid, fire-hardy chaparral and coastal scrub and coastal prairie—the most diverse type of prairie. It also includes a broad array of fresh and salt water wetlands and coastal habitats like dunes and beaches.  to arid, fire-hardy chaparral and coastal scrub and coastal prairie—the most diverse type of prairie. It also includes a broad array of fresh and salt water wetlands and coastal habitats like dunes and beaches." (http://www.sfnps.org/terrestrial)

Aquatic Ecosystems (http://www.sfnps.org)

Terrestrial Ecosystems (http://www.sfnps.org)