Incorporating the ecosystem services provided by coastal beaches and dunes into climate change adaptation planning
Extreme events and chronic stressors associated with climate change, such as intense storms and sea level rise, can have severe impacts on humans and the ecosystem services upon which they depend. Variability in destruction from storms has highlighted the value of natural barriers formed by coastal ecosystems, so called green infrastructure, in reducing vulnerability. There is a growing recognition that beaches and dunes provide critical ecosystem services; they are the first line of defense against flooding, provide conservation value for native species, and are a draw for recreation. Beach and dune protection services are intrinsically linked to sediment supply, vegetation, and their feedbacks. Climate change and other human caused perturbations influence both the physical and ecological processes, and reciprocal feedbacks, significantly affecting ecosystem services. Thus, there are tradeoffs inherent in any adaptive planning exercise, which require an accurate knowledge of services that may be compromised or enhanced by planning decisions. We first examine the relative role of vegetation in determining dune geomorphology in the US Pacific Northwest (PNW) and how dunes of different shapes result in variable levels of exposure to hazards, then describe how this work is being incorporated into conservation and coastal community adaptation planning in Oregon.
Through a suite of field, laboratory, mesocosm, and computer modeling exercises we have documented that PNW dune shape is primarily a function of sediment supply and the non-native beach grasses, Ammophila breviligulata (American) and A. arenaria (European), introduced in the early 1900s. A species-specific biophysical feedback occurs between sand deposition, growth habit, and growth-habit-mediated sand capture efficiency, resulting in distinctly different dune shapes depending on grass species dominance. Coastal hazard modeling shows that grass-created foredunes provide a formidable barrier to extreme coastal waves and sea level rise but also have negative effects on the conservation of endemic species prompting the creation of Habitat Restoration Areas (HRAs), These conservation actions result in a conundrum: with HRAs, dune ecosystem structure and function are somewhat restored but it comes at a cost to coastal protection and beach recreation services. Through deep engagement with a coastal Knowledge-to-Action Network (KTAN), we are incorporating the ecosystem services provided by beaches and dunes into climate change adaptation and conservation planning for vulnerable communities along the Oregon coast. We are taking a spatially explicit scenario-based planning approach to examine interactions between the coupled human and natural coastal system and to evaluate the tradeoffs between ecosystem services.