Historical Ecology

Historical T-Sheet Interpretation

Much of California wetland policy is based on a study that concluded that California has lost 91% of original wetlands within the state (Dahl, 1990). This number is an aggregate of all wetland types, and we wondered, what does that mean for a specific wetland type like Bar-Build Estuaries? As part of our ongoing Bar-built Estuaries assessments, CCWG wants to learn what services these systems provided in the past, that they are no longer able to provide. Our goal is to create a tool to help resource managers prioritize conservation and restoration funds. We have completed a historical change analysis of 33 coastal lagoons throughout the State. Another 20 sites from the North part of the Central Coast have been started as part of a partnership with State Parks. We will soon be adding even more sites to the inventory. The methodology for this is simple and in no way constitutes a full Historical Ecology Assessment.

We have created a tool and foundational dataset for a habitat comparison looking at the T-sheet and 2012 aerials. Only T-sheets used for historical data, though we verified current habitats in the field. For our purposes, sites that are no longer BBEs (such as harbors) were not considered for this assessment. By creating polygons in GIS that encompass the entire BBE area for both current and historic extent, we could then use the “cut polygon feature” tool to trace the habitat types. We classify them into three levels of increasing precision and decreasing certainty. Once all the habitats are classified, we can easily compare the change over time between a site, or a region, or the entire state.

The results from the 30 sites show that the “wetable lowland” habitat, which includes the marsh plain and flood plain, has been most impacted. The largest increase is in developed land. This section will be updated as more results come in. Details about the methods can be found in the BBE Final Report.


Gabilan Historical Ecology Project

In 2007, CCWG initiated an effort to compile current and historical maps and wetland descriptions to expand the historical ecology efforts of SFEI and Elkhorn Slough to the Gabilan watershed. CCWG hosted a practitioner orientation that focused on wetland management questions and available historical data resources that can help address these issues with the agreement that "understanding the form and function of a slough prior to the late 1800s can inform interpretation of the current hydrologic regime and perhaps aid recovery and restoration in progress today" (SFEI 2007)

The initial pilot program, in partnership with Joel Cassagrande at CSUMB, focused on the compilation of historical maps and literature for the Gabilan Watershed. This information will help direct possible restoration efforts through better understanding of coastal wetland function in the absence of significant human management. Joel compiled historical maps and anecdotes for the Gabilan watershed and has created a timeline (timeline.pdf). This effort has been a great start to the historical ecology project for the Gabilan Watershed.

Link to Historical Maps

Below is a library of Historic literature about the Gabilan Watershed.

  • Woodpeckers of the Upper Salinas Valley (pdf, 705kb), Thompson, Chas, 1900
  • Land Forms and Land Use East of Monterey Bay (pdf, 1.2mb), Beard, Charles, 1948
  • Historic Fire Regimes and Their Relation to Vegetation Patterns in the Monterey Bay Area of California, Greenlee, Jason and Langenheim, Jean, 1990
  • Lettuce Industry of the Salinas Valley (pdf, 1.2mb), Griffin, Paul F. and White, C. Langdon, 1955
  • From Field and Study (pdf, 397kb), Silliman, O. et al, 1915
  • Water Rights Case – Decision Approving Application (pdf, 623kb), SWRCB, 1976
  • Summer Birds of the Upper Salinas Valley and Adjacent Foothills (pdf, 426kb), Willet, G., 1908
  • Field Notes of The Reservation and Examination made in the City Lands of Monterey (pdf, 33kb), Hermann, A.T., 1879

In addition to published literature, there are a number of recorded anecdotes about the Gabilan Watershed. These include newspaper articles and excerpts from books.