Preserving Biodiversity for a Climate Change Future: A Resilience Assessment of Three Bay Area Species--Adenostoma fasciculatum (Chamise), Arctostaphylos canescens (Hoary Manzanita), and Arctostaphylos virgata (Marin Manzanita)
Date of Graduation
Master of Science in Environmental Management (MSEM)
College of Arts and Sciences
Anthropogenic climate change is an undeniable threat to the future of the natural world and human civilization. These shifts will have profound impacts on vegetation, especially for species endemic to isolated regions or sensitive to climate change factors. However, species resilience can predict success into the next century. Resilience is defined as the ability to withstand climate change factors, whereas vulnerability is defined as susceptibility to climate induced stress or damage.
Chaparral and coastal scrub ecosystems within the Bay Area of California provide a unique context for examining resilience, as many species are adapted to high temperatures, drought, and wildfire—all elements predicted to increase with impending climate change. Through a comparative analysis of three species, the physiological and geographic adaptations that lend to resilience were assessed, along with estimations for potential range shifts and population decline. The three species are:
1. Chamise (Adenostoma fasciculatum) – A dominant shrub species projected to increase in biomass in climate change scenario models
2. Marin Manzanita (Arctostaphylos virgata) –A rare, endemic shrub species with declining populations
3. Hoary Manzanita (Arctostaphylos canescens) – A species with paleo-ecological records traced to northern, cooler regions
Of these chosen species Adenostoma fasciculatum was determined to be the most resilient due to a high threshold tolerance of climate change factors and small seed size. This species will likely spread throughout the Bay Area and become increasingly dominant as a result. Arctostaphylos canescens was determined to be the most vulnerable due to projected heat stress, likely drought stress, and large seed size. Potential refugia for the species within the study area exists in San Mateo County and assisted migration is a potential option to ensure success into the future. Lastly, Arctostaphylos virgata was determined to be en situ refugia, and therefore will likely persist in its current range. Although it is the most sensitive species, it exhibits resilience because its range is within an area where projected temperatures are lower than the suitability threshold. Results were determined by comparing species suitability traits to coarse climate projections as well as comparing factors of recruitment, temperature, fire disturbance, temperature exposure risk, water uptake risk, and plant height. Of the resiliency traits examined in literature review, seed mass and species adaptability were determined as the most important for discerning future success by allowing species to expand in range and move into suitable habitat. This research framework can be replicated to analyze vulnerability or resilience for most vegetation in most ecosystems.
Pollack, Alison S., "Preserving Biodiversity for a Climate Change Future: A Resilience Assessment of Three Bay Area Species--Adenostoma fasciculatum (Chamise), Arctostaphylos canescens (Hoary Manzanita), and Arctostaphylos virgata (Marin Manzanita)" (2016). Master's Projects. 352.