On 26-27 October 2010, we hosted a workshop in Berkeley, California entitled ―Modeling Effects of Sea Level Rise on the Ecology of Shoals and Migratory Birds.‖ The two-day workshop invited 20 participants including invited speakers, research scientists, and resource managers. Expert modelers invited to participate included Dr. Dano Roelvink (Deltares, Netherlands), Dr. Neil Ganju (USGS Woods Hole Science Center), and Dr. Noah Knowles (USGS Menlo Park Science Center). The overall goal was to discuss modeling approaches and identify linkages between physical and biological models about this critical topic. Results from the discussions indicated that modeling sea level rise (SLR) effects on shoals was both feasible and timely with several complementary efforts (see below). A brief summary of key modeling topics are presented in following paragraphs.
Avian ecology on shoals: Prey quality, abundance, distribution, and accessibility influence bird carrying capacity and population health. Prey and physical characteristics interact to determine the area available for foraging. Although invertebrates are primary food on shoals, biofilm may be a key food source for some smaller shorebirds. Physical factors influence prey abundance and availability, while habitat use is affected by proximity of suitable roosting or nesting areas. Some of these datasets are available from existing USGS shoals research studies.
Biophysical interface: Physical drivers on biota include tidal inundation and exposure, salinity, temperature, water depth, and sediment type. Phytoplankton dynamics are an important interface between physical processes and invertebrate response. Predation pressure is determined by water depth, slope, movement of the tide line, and sediment permeability. Maintenance of biofilm requires sufficient light and low turbidity, and biofilm may determine cohesiveness of sediments. USGS Western Ecological Research Center currently is working on biofilm foraging by shorebirds in cooperation with world expert Dr. Tomohiro Kuwae.
Geomorphic modeling: Downscaled global climate change models provide temperature and precipitation predictions to determine potential effects on hydrology. Delta inflows, winds, and SLR are used to model changes in hydrodynamics, sediment transport, and geomorphology. Hourly Golden Gate tides are modeled with global SLR scenarios, El Niño, storm surges, barometric pressure, and tides, and outputs include water levels, floodplain expansion, and sediment availability that are inputs to estuarine geomorphic models of tidal flat change. Delft-UNSTRUC model with 3-D grids may be used to simulate hydrodynamics, sediment, geomorphology, salinity, and temperature along a continuum of ocean to river under one model framework. We will
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coordinate this model with ongoing development of the USGS-led models under CASCaDE (Computational Assessments of Scenarios of Change for the Delta Ecosystem).
Habitat connectivity: There is an integral link between destruction and formation of tidal flats and marshes. Marsh erosion and storm action are integral to the modeling. Work will be coordinated with USGS hydrodynamic studies at Corte Madera marsh, conducted in cooperation with the Army Corp of Engineers and the Bay Conservation and Development Commission.
Extreme events: Frequency or severity of extreme events should be assessed with sea level rise. Historical datasets are critical to identify effects on birds and mud flats. Parameters include: rate and degree of sea level rise, frequency and severity of storms, extreme high tide events, marine influences (upwelling, North Pacific Gyre Oscillation, and El Niño), and acidification.
Key modeling parameters: Habitat metrics include physical influences on avian foraging and prey accessibility (water depth, slope, movement of tide line, and sediment permeability), as well as factors determining the suitability of food sources. Density, distribution, biomass, and size classes of invertebrates are dependent on tidal inundation-exposure regime, predation pressure, water quality, benthic conditions, phytoplankton, and seasonally-variable external forcing factors.
