What is Biodiversity?

Biodiversity, or “biological diversity,” refers to the variety of plants, animals and other living things in a particular area or region. It includes genetic variety, species diversity, and variability in communities, ecosystems, and landscapes.

San Diego County is very rich in biodiversity. In fact, San Diego has more biodiversity than any other county in North America and, along with the rest of California, is among the top 10 biodiversity regions on earth. The mild, Mediterranean climate (hot dry summers and cool, wet winters) and varied landforms create a number of distinct habitats, including: beaches, salt marshes and lagoons, coastal sage scrub, grasslands, chaparral, oak woodlands, streamsides, mixed conifer forests, freshwater marshes and meadows, and desert.

Scientists describe our region as a conservation “hotspot” because of the vast numbers and variety of threatened and endangered species that reside here. Many of these species are endemic. “Endemic” means that a species is native to a specific geographical area, such as San Diego County, and found nowhere else in the world.

Some of the rare, threatened, and endangered species in San Diego County are listed below.

Rare, Threatend and Endangered San Diego Species

According to biologists, human activities are the primary cause of ongoing species decline and extinctions. Because of the ever increasing size of the human population and its exponential rate of resource consumption, the environmental impacts of humans are quite significant and, in some cases, irreversible.

Human activities contribute directly to species loss through habitat degradation and destruction, pollution, introduction of non-native species into natural habitats, and overexploitation of wild plant and animal species. For exmple, urbanization and related habitat encroachment, expansion of large-scale agriculture, road construction, livestock grazing, logging, strip mining, and oil extraction have reduced California’s wetlands, riparian forests, and coastal sage scrublands to 10 percent of their original habitat area, and native grasslands and vernal pool habitats to 1 percent of their orginal habitat areas.  Human pollution, particularly, has now been linked to significant physical and biotic changes at all levels, from local ecosystems to the global climate change.  California is one of the four most ecologically degraded states in the United States and contains some of the country's most endangered ecosystems. More of California's plant and animals species (250) are protected under the U.S. Endangered Species Act than in any other state, and 180 more are proposed for listing.

Our everyday actions can have an impact – positive or negative – on the health of San Diego’s native habitats and the plants and animals found there.

Photos by Barbara Barnes

Hiking Vulcan Mountain near Julian                                  Clark Valley in Anza-Borrego State Park

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Shore Gull near Encinitas                   Photo by Barbara Barnes

Why is Biodiversity Important?

The value of protecting and maintaining the biodiversity of our region is ecologic, economic, and esthetic.

Species of all types, no matter how small, play an important role in an ecosystem (a community of plants, animals, and microorganisms that are linked by energy and nutrient flows and that interact with each other and with the physical environment). It is this combination of species and the roles that they each play that enables an ecosystem to recover from a variety of disturbances, including fire. Some of the benefits of a healthy and vital ecosystem include:

•recycling and purification of water and air through the regional watershed system
•mitigation of climatic and weather extremes (e.g., floods and drought, winds

  and waves, fire)
•breakdown and detoxification of pollution
•cycling of nutrients
•re-generation of fertile soils
•pollination of crops and wild plants
•control of agricultural pests by natural predators and parasites
•and, the continual renewal of biological diversity that supports all of the above

 © D.L Green (2001)                                                              Photo By Douglas Aguilard

       Bee pollinating Horesmint                                      Santa Margarita River near Fallbrook

In short, biodiversity helps sustain the outstanding and unique environment in which we live. It also enables us to obtain direct benefits, such as, tangible materials (wood, paper, rubber, limestone, coral), genetic resources (used in agriculture and biotechnology), chemical discoveries (incorporated into medicines, chemical engineering), and food (local citrus, strawberries and other fruits, avocados, vegetables, eggs, honey, poultry and beef)

Clementine tangerines

The degree to which medicinal knowledge is based in biological diversity is particularly striking. For example, of the top 99 prescribed compounds (found in the top 150 prescription drugs), 53% have their origins in species of animals, plants, fungi, or bacteria. When estimates of discovery rates of medicinally active chemicals are combined with estimated extinction rates of species, scientists conclude that about three potential new medicines are being lost each year due to losses of biological diversity.

Julian apples                                                                                           Photo by Barbara Barnes

Finally, the variety in the natural world—plants, animals, terrain, habitats--is beautiful and serves as a source of wonderment and great enjoyment for many people.

      Hermes Copper butterfly (rare - found only in San Diego County )             Photo by Douglas Aguillard

What Can We Do To Conserve Biodiversity?

Learn about your entire community. For example, where does your water come from? ... How does food get to your table? … Where is your clothing made? Explore the natural places around you, such as, San Diego's wilderness areas. Take note of the diversity of the plants and animals where you live. By understanding and appreciating how your daily choices affect San Diego’s remarkable biodiversity, you can join with others in helping conserve it.

              Mission Trails Regional Park                                                                        Photo by Scott Streit

Sources: Adapted from

American Museum of Natural History, Center for Biodiversity and Conservation. (2005). Biodiversity. Retrieved January 27, 2005 from http://research.amnh.org/biodiversity/index.html

California Department of Fish and Game. (2005). California's plants and animals. Retrieved January 26, 2005 from http://www.dfg.ca.gov/hcpb/species/species.shtml

Conservation International, Center for Applied Biodiversity Science. (2005). Biodiversity hotspots. Retrieved January 25, 2005 from http://www.biodiversityhotspots.org/xp/Hotspots

Reiser, C.H. (2005). Rare plants of San Diego County. Retrived January 25, 2005 from http://sandiego.sierraclub.org/rareplants/

San Diego Zoo. (2005). San Diego's habitats (PDF). Retrieved Janaury 21, 2005 from http://www.sandiegozoo.org/teachers/habitat_booklet.html

World Wildlife Fund. (2005). Biodiversity 911 on the web; Biodiversity basics. Retrieved Jnauary 27, 2005 from http://www.biodiversity911.org

Photo Credits:

Aguillard, D. (2005). The birds, butterflies, & dragonflies. Retrieved January 29, 2005 from http://sdbirds.basiclink.com/index.html

Barnes B.E. (2004). Assorted photographs from San Diego County, 2004. WhiteSage Cafe@AOL.com

Green, D.L. (2005). Pollination homepage; bee pollinating horsemint (photo). Retrieved January 29, 2005 from http://pollinator.com/

Streit, S. (2005). Bird friends of San Diego County. Retrieved January 29, 2005 from http://www.bird-friends.com/