Channel Islands Chapter
Education: Biodiversity Hotspots

Biodiversity Hotspots

By David M. Brown and David L. Magney

What is a Biodiversity Hotspot?   It is a place on Earth that has an unusually high number of different species, more per square kilometer/mile than most other areas of the planet.   Organizations like Conservation International have identified 25 biologically diverse places on the planet, recognizing each for its uniqueness and especially for its extraordiarially high number of species of plants and/or wildlife.   California is one of those 25 biodiversity hotspots.

California Biodiversity Hotspot

Did you know that you live in one of the most significant regions of biological diversity on Earth?   California is one of the 25 most biologically diverse places on the planet, and is the only biodiversity hotspot in North America.   Biological diversity (or biodiversity) is a measure of ecosystem health and function. The California Public Resources Code Section 12220[b] defines biodiversity as the number and genetic richness of different individuals found within the population of a species, of populations found within a species range, of different species found within a natural community or ecosystem, and of different communities and ecosystems found within a region.

California has at least 2,153 endemic taxa of vascular plants (species, subspecies, varieties).   This means that 34% of the 6,272 native plant taxa in California are found nowhere else on the planet.   Many plant species, subspecies, and varieties have evolved in ecological niches created by the unique confluence of climate, topography, and soils found in California and nowhere else on the planet.   California has many different landforms in close proximity that interact with climate and soil to produce multiple niches for evolution that do not exist in other areas of North America.   California can therefore be considered an “evolutionary pump” generating more endemic species than any other region of the United States.

California has not only the highest number of endemic plant species in North America, but also the highest amount of plant ecological richness as defined by the number of plant associations.   A plant association is a group of plant species that is defined by the most dominant plant species in the grouping. California has over 2,000 types of plant associations, which is about 50% of the known plant associations in the United States.

The California Biodiversity Hotspot continues to get hotter every year as an estimated ten new species of endemic plants are discovered every year in California.   There may be hundreds of other endemic species waiting to be discovered.   There are four areas within the California Biodiversity Hotspot that glow more than the rest: the Sierra Nevada, the Transverse Ranges, the Klamath-Siskiyou region, and the Coast Ranges.

The California Biodiversity Hotspot contains the highest numbers of endemic amphibian and mammal species in North America.   There are 51 species of amphibians (frogs, toads, and salamanders) in California, of which 17 are endemic.   There are 17 endemic mammal species in the California Biodiversity Hotspot including the Channel Island Fox found off the coast of Ventura County and the Mount Pinos Chipmonk in northernmost Ventura County.   As of 2003 (Roth and Sadeghain 2003 - Checklist of the Land Snails and Slugs of California. [Santa Barbara Museum of Natural History Contributions in Science No. 3.] Santa Barbara, California.), there were known to be 360 terrestrial gastropod taxa native to California.   A good many of these species (including subspecies/varieties) of terrestrial gastropods are endemic to California.

Ventura County, a Bright Light in the California Biodiversity Hotspot

Ventura County is within the Transverse Ranges.   Ventura County is one of the hottest spots of plant diversity within the California Biodiversity Hotspot.   Currently, there are 1,817 species (including subspecies, varieties, and natural [stable] hybrids) of California native plants known within Ventura County (including Anacapa Islands and San Nicolas Island).   As of today, there are eleven species of plants that occur only in Ventura County, including:

These are all Ventura County endemics, meaning they only grow naturally in Ventura County.   That is more endemic species than occurs in several entire states (including: Alabama, Connecticut, Indiana, Iowa, North Dakota, Ohio, Pennsylvania, and Rhode Island ), and probably several more.   We have at least two rare and endangered California-endemic plant species in Ventura County that are special because they have come back from the dead (or what was thought to be extinction), the Ventura Marsh Milkvetch and the San Fernando Valley Spineflower (Chorizanthe parryi var. fernandina).

The Ventura Marsh Milkvetch (Astragalus pycnostachyus var. lanosissimus) is a member of the pea family first discovered in the late 1800s that was thought to be extinct in the wild after last being seen in 1967 at McGrath State Beach, having been mowed down.   A small population was rediscovered at an old oil waste dumpsite near Oxnard in 1997 (the North Shore development site).

The San Fernando Valley Spineflower, a member of the knotweed or buckwheat family, was discovered in 1887 and then last seen in 1929, and presumed extinct.   It was rediscovered in 1999 on Laskey Mesa at the Ahmanson Ranch development site, and then discovered on Newhall Ranch.   It now exists only at Newhall Ranch and Ahmanson Ranch in Los Angeles and Ventura Counties.   (Visit the Conservation Issues webpage for stories on these projects.)

Bryophytes and lichens are two other groups of plants that are also part of the biodiversity of Ventura County (and California, of course.   Due to their diminuative size and minute parts, they are too often ignored by the public and biologists alike.   Bryophytes, which include liverworts, hornworts, and mosses, are "primitive" plants that lack vascular tissues to conduct fluids and nutrients to various parts of the plant.   Therefore, bryophytes are quite thin, with leaves only one or two cells thick.   Even when they look dead, they are alive.   Just add water and you can watch them come back to life.   Currently, we know there are at least 95 species of bryophytes in Ventura County, which surely represents a low count.

Lichens are strange life forms that are made up of two components, a fungus and an algae (sometimes a blue-green algae).   The combinations of specific algae and fungi combine to create unique species that come in three basic life forms: crustose, foliose, and fruticose (Visit Magney's lichen webpage for some examples).   Crustose lichens are those found closely attached, and even imbeded in rocks and bark, and other substrates.   Foliose lichens are more leafy looking and not as tightly attached.   Fruticose lichens are usually intricately branched, looking like little bushes (and are often used as fake bushes and trees in models of urban scenes).   Lichens come in many colors, sometimes very bright colors.   There are at least 150 lichen species in Ventura County, with at least 20 that are rare.   Information about California lichens, including preliminary lists of species from California counties are available from the California Lichen Society website.

While there are no mammals or birds known to be endemic to just Ventura County, one small chipmonk, the Mount Pinos Chipmonk, lives in northernmost Ventura County and along the southwestern edge of adjacent Kern County.   There are at least three species of terrestrial gastropods endemic to Ventura County:   Ventura Shoulderband Snail (Helminthoglypta venturensis), Matilija Shoulderband Snail (Helminthoglypta willettii), and Sage Shoulderband Snail (Helminthoglypta salviae salviae).   While little is known, really, about the invertebrates, and what species are endemic to Ventura County, there is at least one species of walkingstick, the Santa Monica Mountains Walkingstick (Timia santamonicae), that is known only from the Ventura County end of the Santa Monica Mountains.

Obviously, with such diversity and species richness in California and Ventura County, you can see that it is truly a special place.   Because of our rich natural biological resources, all actions by humans that may adversely impact these resources must be carefully thought out.   Short-term economic gains are not valid reasons to permanently destroy our natural heritage.

For more information about California native plants, visit the California Native Plant Society website and other pages on the Channel Islands Chapter website for more local information.   For detailed information about the plants of Ventura County, visit Magney’s Ventura County Flora website.   For more information about native terrestrial gastropods (snails and slugs), particularly of those from Ventura, Santa Barbara, and Los Angeles Counties, visit the Sespe Institute’s website.   For more information about biodiversity of North America, visit the Biota of North America Project (BONAP) website.   For more information about biodiversity hotspots, visit Conservation International’s website.   You may be surprised about what you learn.

Special thanks to Carlin Moyer for the beautiful illustrations on our site.

Created: 20 October 2011.   Last updated: 4 February 2012
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