GEOG/ES&P 330

California Ecosystems

Links Illustrating Lecture on Environment of California

Mediterranean climates

World pressure and wind system

Tilt in Earth's axis changes location of direct ray of sun

Movement of pressure/wind system with movement of solar direct ray

Disruption of pressure belts by continentality and marine effects

• January: Northern oceanic pits of low pressure
• July: Northern oceanic peaks of high pressure

Note how winds move around highs and lows in Northern Hemisphere

Gyres and relatively warm and cool currents offshore

So, Mediterranean climates are two-season climates on the west coasts of continents in subtropical latitudes (30°-40° N or S) with hot, dry summers and cool, often rainy winters. These are produced by:

• our position with respect to movement of the world pressure and wind pattern
• this pattern is a rotation-distorted convection heat engine that moves to follow the most intense direct rays of the sun
• the direct ray of the sun moves because of the obliquity of the planet's rotational axis
• we have a dry summer because the breakup of the Horse Latitudes into oceanic peaks changes wind circulation so that wind spirals over the cold California current offshore and depletes the air of moisture (Back East, the spiraling circulation out of the Bermudas High pushes air over the hot Gulf Stream, which makes it very humid)
• the cold California current and the hot Gulf Stream are portions of the gyres of surface currents that form in the world's oceans
• The upshot is a very challenging environment for plants

Current state of winds around the world

Further complicating the local pattern of climates in California is the rough topography, itself the result of plate tectonics

• Terrain of Southern California
• Adret and ubac slope aspects
• Windward and leeward slope aspects and rainshadows

California's climates and microclimates are very challenging to plants and, because of the environmental diversity, there is terrific biodiversity here. We are recognized as a "biodiversity hotspot," which means an area that, in global comparison, is extremely biodiverse and, because of its popularity with humans, under threat.

California is one of around two dozen global biodiversity hotspots

We'll spend quite a bit of time on California sage scrub (CSS), which has lost 85 or 90 percent of its original extent and is highly endangered -- and biodiverse -- and critical habitat for endangered animals.

California Sage Scrub map (CA)

CSS map (SoCal)

CSS landscape

CSS landscape

CSS landscape

Common plants in CSS:

• Artemisia californica

• Salvia leucophylla

• Salvia mellifera

• Eriogonum fasciculatum

• Eriogonum cinereum

• Baccharis pilularis

• Encelia californica

• Rhus integrifolia

• Heteromeles arbutifolia

Endangered animals dependent on CSS:

• California gnatcatcher

• Cactus wren

• California rufous-crowned sparrow

• Palos Verdes blue butterfly

• Pacific pocket mouse

• Orange-throated whiptail lizard

 

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Document maintained by Dr. Rodrigue
First placed on web 08/15/15
Last revision: 08/25/21