San Francisco Bay Estuarine-Upland Transition Zone - Ranked Restoration Potential

This vector layer represents the distribution of potential tidal marsh-upland transitional zone habitats (aka ecotones) within South and Central San Francisco Bay and ranks their restoration potential for assisting with tidal marsh ecosystem conservation. This layer contains transition zone habitat polygons (for south SF bay) with an attribute for each metric and total rank. Current transition zone habitats are ranked according to habitat "quality" as defined by a range of metrics of habitat function (Thomson 2013). The dataset is designed to assist land managers in prioritizing transitional geography (i.e. land surfaces with the proper elevation) based on their potential value to the protection and restoration of the San Francisco Bay Estuary. 

The dataset is a component of a larger DSS, which includes maps of transition zone distributions under 61cm and 167cm of sea level rise (SLR) and a document providing a functional definition for transition zones. This dataset and DSS can also assist users to account for the landward migration of transitional habitats in response to projected sea level rise.

All supporting materials (including google eath versions of datasets) can be found at http://climate.calcommons.org/dataset/san-francisco-bay-estuarine-terrestrial-transitional-zone-decision-support-system

The DSS includes 3 major components: (1) GIS models of the current and future (2050 - 61cm SLR and 2100 - 167cm SLR) distribution of transitional habitat patches, based on documented tidal elevations, at the landscape level; (2) GIS models of ranked (existing and potential) transitional habitats based on site specific indicators of patch “quality” for restoration; and (3) a technical document that describes and characterizes transitional habitat based on how it can support the ecological functions of the tidal marsh ecosystem . This toolkit will help managers allocate limited resources on site prioritization, alternative/scenario evaluation, and includes considerations for the influence of future climate change and land-use scenarios.

With the help of tidal marsh ecosystem specialists throughout the region we drafted a thorough description of tidal marsh-terrestrial transitional habitats. This document characterizes the physical and biological properties of upland transitions with respect to the functions of the tidal marsh ecosystem and needs of obligate fauna. 

A list of habitat indicators and GIS metrics were developed based on these functions, which were utilized to map their distribution and assess their quality (see Thomson 2013 and Fulfrost and Thomson 2015 available at link above). The six primary indicators identified include (metrics listed below):

1. Elevation in relation to tides (needed for plant community, high tide refugia for obligate fauna,and SLR adaptation)

2. Depth and slope of transitional zone (distance needed by tidal marsh fauna and flora, SLR adaptation)

3. Size and Shape (as needed by tidal marsh fauna and flora, overall estuarine function)

4. Adjacent Habitats and Connectivity (as needed by tidal marsh fauna and flora, overall estuarine function)

Although most indicators were mapped throughout the estuary, our pilot study focused on the South Bay (San Francisco Bay). Work is currently underway to complete the DSS for San Pablo and Suisun Bays (including transition zone distribution and SLR projections for the entire bay) and to provide a series of improved rankings for habitat enhancement, restoration and creation.