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Conservancy Has Important Role to Play for Future of California Coastal Sage Scrub

by Phil Rundel, Rasoul Sharifi, and Erin Riordan
UCLA research group on the ecology and conservation of California sage scrub

 

The Conservancy manages ten open space reserves in Rancho Palos Verdes, which include sizable sage scrub communities. These reserves benefit, protect and conserve important habitat in order to preserve sensitive plants and wildlife. The Forrestal Reserve, one of these ten reserves, provides an excellent example of diverse sage scrub habitat and is home to a number of animals and plants of special concern. These include the California gnatcatcher (Polioptila californica californica) and the ocean milk vetch (Astragalus trichopodus var. lonchus), one of the host plants for the endangered Palos Verdes blue butterfly. 

Our UCLA research group has been carrying out studies on sage scrub for a number of years, using the Forrestal Reserve as a research location and outdoor lab for students from K-12 students through college. This outreach program helps participants learn about the significance of plant and animal communities in this unique habitat and helps to promote greater appreciation for the importance of protecting this endangered ecosystem.

As one of the most threatened vegetation types in Southern California, coastal sage scrub continues to face widespread loss, fragmentation and degredation from land development, urbanization, changes in fire regime, invasive plant species, and air pollution over the past century. Today, sage scrub covers only a small fraction of its original habitat. Because of this, many plant and animal species associated with sage scrub are categorized as sensitive, rare, threatened, or endangered, and these species face an uncertain future in Southern California. 

Complicating predictions about the future of sage scrub communities in Southern California, global climate change and human population growth continue to increase.  By the end of the 21st century, scientists expect that the climate of Southern California will change substantially, as temperatures rise and droughts increase in frequency and severity. A rapidly warming and drying climate this century could cause sage scrub communities to shift their ranges to more favorable climates, disappear from their existing range, decline in diversity as individual species are lost, or be overtaken by weedy non-native species. At the same time, increasing human populations and associated land-use changes will cause additional loss of wildlands.

Incorporating scenarios of future environmental change into conservation and resource management is challenging but increasingly important. Evidence of the significant ecological impacts of climate change are already becoming evident in California, providing new data to help environmental scientists and climatologists to better predict potential ecological impacts as the climate continues to warm and dry into the future. By the end of the century, our climate modeling studies predict that dominant sage scrub species will lose considerable habitat in Southern California due to climate change, with many species losing a third or more of their present habitat range. These predictions are of great concern given the diversity of threatened and endangered species associated with sage scrub in Southern California.

With these threats in mind, it will become increasingly critical to preserve existing stands of sage scrub and restore sage scrub habitat in the future. The Conservancy has an important role to play in these conservation efforts.

Measuring Coastal Scrub in Forrestal