UCLA

Coastal wetlands are considered one of the most productive natural ecological infrastructures in the world. Although coastal ecosystems total only 6% of global surface area, they provide an estimated 38% of global ecosystem services. Despite their environmental and societal value, coastlines and coastal habitats are increasingly threatened by human activity. Human threats include proximal disruptions such as wetland removal, changes in sedimentation and chemical pollution. Additionally, climate change, and more specifically sea-level rise (SLR) poses one of the greatest global threats to coastal marshes. Estimates for future SLR rates range anywhere from 0.3 m to over 1.3 m by the end of the 21st century. While historical observations have shown that tidal wetlands can tolerate and dynamically adjust in elevation to some rate of SLR, there are limits. Human population growth, coastal development and the concept of coastal squeeze constrain landward vertical migration of marshes and bring in additional factors that challenge efforts to understand and manage future salt marsh trajectories. Indeed, humans are integrated into the very fabric of major processes governing wetland stability, which can have major impacts on ecogeomorphic feedback systems and overall marsh resiliency. Thus, local anthropogenic stressors should be coupled with climate change impacts in management and conservation efforts, as they often interact synergistically. However, to do so effectively requires communication and unified actions by stakeholders, managers, and scientists. In the following dissertation, I plan to tie these themes together by researching the multiple human and climatic stressors on California coastal marshes and creating knowledge that can be used in science-policy settings. Furthermore, I use a participant-observer approach to study the communication and planning for mitigating coastal threats in California. First, I obtain high-resolution geochemical data from three coastal marshes in the San Francisco Bay to look at responses to recent anthropogenic changes in sedimentation and pollutant loadings in the context of marsh conditions and histories since the mid-Holocene. Next, I look at attempts to mitigate the impacts of SLR through a large-scale sediment addition project in Seal Beach National Wildlife Refuge, CA. I use the analysis of sediment cores, to understand natural accretion and variability over time and how it compares to the artificial accretion and sedimentation from sediment addition. Lastly, I utilize information from a longer-term participant-observer project updated and augmented with my own participant-observer experience with the SWCASC funded coastal workshops to provide an analysis on knowledge co-production efforts in coastal management settings to understand what makes knowledge relevant in management and policy contexts.