Multi-Species Conservation in the Context of Global Change

The earth's biodiversity has been severely adversely affected by global change driven by human population growth; the major threats include habitat loss and fragmentation, altered disturbance regimes and climate change. Unfortunately these anthropogenic impacts are not diminishing and in order to minimize future adverse effects on biodiversity it is important to understand their relative and cumulative effects. In addition because they impact entire ecosystems comprised of species with differing population responses to threats and management, multi-species conservation planning methods are needed that explicitly consider trade-offs among species. In Chapter I, I evaluate patterns of plant endangerment in three regions of California with respect to land use and human population density using data from the State Natural Heritage Program. I found no evidence to suggest that at-risk plant species fared better in areas with lower human population density and concluded that populations within disturbed landscapes can contribute to overall biodiversity conservation. I developed habitat suitability models (Appendix A) and population demographic models (Appendix B-E) for four species of the coastal maritime chaparral in coastal southern California: Ceanothus verrucosus (wart-stemmed Ceanothus), Chorizanthe orcuttiana (Orcutt's spineflower), Neotoma macrotis (big-eared woodrat) and Quercus dumosa (Nuttal's scrub oak). In Chapter II, I conducted a multi-threat analysis for Ceanothus verrucosus, asking the question, does climate change pose a more serious threat than the more proximal threats of altered fire regime, and habitat loss and fragmentation. I found climate change to be the most serious threat but that interactions among threats increases the risk of extinction for this species. In Chapter III, I presented an approach to multi-species conservation planning that explicitly takes into account species trade-offs in response to threats and management. The resulting methods rely on a combination of single patch and metapopulation models, habitat suitability models, and quantitative conservation objective functions to explicitly address species trade-offs under multiple threats from global change.