about the biome: California/Baja California

© Darin Busby

Geography and topography

With a total land area of 123,000 square kilometers, this region includes most of the state of California west of the Sierra Nevada Mountains and a small adjoining portion of the Mexican state of Baja California (also known as Baja California Norte). The topography is as varied as it is beautiful, featuring coastal mountain ranges, the foothills around the long Central Valley, and the Channel Islands off the Pacific shore. Mild winters, abundant sunshine and miles of coast naturally draw people to this region, which is home to three of California's largest metropolitan areas: the Los Angeles basin, the San Francisco Bay area, and the San Diego region (Dallman, 1998). Approximately halfway between San Francisco and Los Angeles lie stretches of coastline - such as Big Sur - that are among the least developed and most scenic of any of the Mediterranean regions (Dallman, 1998). We hope to keep it that way.

Vegetation and plant life

This area supports more plant species than the territories of Canada and the central and northeastern regions of the United States, which are ten times its size (Dallman, 1998). Many native species endemic to the area have evolved as a result of geologic isolation and unique soils and climate (Sharsmith, 1982). Different rock types, juxtaposed by tectonic shifts and related forces, have created an unusual diversity of vegetation (TNC Central Coast Ecoregional Plan, 2006). Many of the region's plants have adapted to grow exclusively on unique soils such as serpentine - an estimated 20% of rare endemic plants grow in serpentine soils (CDFG, 2003). As a result of human activity, many of these species have become rarer still.

The region's remarkable geography is reflected in the richly varied vegetation patterns. Among the vegetation uniquely native to this region are the coastal redwood forest, blue oak woodlands, closed-cone pine and cypress forests, and the mixed evergreen forest (Barbour and Major, 1988). Dating back to the age of dinosaurs (Dallman, 1998), the coastal redwood forests include the world's tallest trees and some of the oldest trees on earth. They live for more than 500 years on average, and some reach more than 2,000 years of age.

Many coastal slopes feature coastal sage scrub, chaparral, and annual grasslands, crossed by streams and lined with highly diverse riparian forests (Ornduff, 2003). Near the coast at higher elevations, mixed hardwood forests (Thorne et al.2004; Ornduff, 2003) are interspersed with montane chaparral, meadows and scattered patches of coniferous forests. Oak woodlands, savannas and annual grasslands dominate interior valleys, with chaparral and scrub on the steeper slopes, and seasonal wetlands sparsely scattered across the valley floors. Chaparral is one of the most extensive types of vegetation in this region. Appearing on hot, dry slopes and ridges, it is very vulnerable to fire, which it also needs for its renewal.

Fast Facts

• California / Baja California is the second smallest Mediterranean climate region, with 4% of the biome’s total land area.
  
• This region supports 4,300 plant species, 35% of which are found nowhere else in the world (Cowling, 1996).
  
• More than 400 species are endangered, threatened or otherwise sensitive to human impact (Las Californias Binational Conservation Initiative).
  
• At 17%, this region has the smallest proportion of land converted from natural habitats to other uses (TNC Analysis, In Prep).
  
• The region covers only 1% of the United States, but it is home to almost 10% of the country’s population (TNC Analysis, In Prep).
  
• The area’s population density is nearly double that of any other region – its population grew 13.5% from 1990 to 2000. There were an estimated 32 million residents as of 2000, with 185 people per square kilometer (TNC Analysis, In Prep).
  
• The region’s population is expected to grow by 30% from 2000 to 2015, reaching 42 million (TNC Analysis, In Prep).

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