Print PageClimate change, urbanization and changing disturbance regimes threaten population persistence for species worldwide. However, few studies have quantified impacts of each simultaneously for threatened species and far fewer have quantified the potential value of conservation interventions for population persistence. Here we used an integrated spatial distribution and population viability model to explore the potential impacts of these threats (climate change, urbanization and fire frequency changes) on Ceanothus verrucosus, a rare California plant species. Climate change projections were based on the A2 emissions scenario and two climate models (GFDL and PCM), urbanization was simulated by the SLEUTH cellular automaton model and fire was modeled by a Weibull hazard function. Based on this framework we also examined the potential for land conservation and reintroduction strategies to lessen these anthropogenic impacts on the species. We looked at the difference in risk of population decline between a landscape with public land excluded from development and a landscape with those lands in addition to reserves under the San Diego County Multiple Species Conservation Plan (MSCP). We also identified habitat patches resistant to climate change and modeled relocation from source populations to assess the efficacy of managed relocation as a climate change adaptation strategy.
Results/Conclusions
Our results show that fire return intervals must be maintained at or above a 20 year level for California C. verrucosus populations to remain viable. Furthermore, relative to a status quo scenario where habitat suitability does not change through time, expected minimum abundances (EMAs) are projected to be reduced under urbanization (17% decline relative to the status quo scenario), climate change (GFDL: 53% and PCM: 14% declines), and both climate change and urbanization scenarios combined (GFDL: 75% and PCM: 43% declines). However, both land protection and managed relocation strategies could ameliorate these impacts. For example, EMAs of populations under urbanization are 28% higher with MSCP land protection incorporated. Additionally, reintroductions from source populations to climate change resistant populations can increase EMAs between 5-15%. These results together emphasize the interactive effects and threats of landscape fire regime alterations, climate change and land use changes to populations and biodiversity. However, we also present reasons to be optimistic by demonstrating the utility of conservation interventions such as land protection and relocations for the management of threatened and endangered species.
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