The official website of the Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve
Elkhorn Slough Restoration: Historical Ecology Tools
Historical USGS topographic map of Elkhorn Slough as viewed in Google Earth.

Digging into the Past -
Historical Ecology Tools You Can Use at Home

[LISTEN to Reserve Stewardship Coordinator, Andrea Woolfolk and Stewardship Specialists, Bree Candiloro interviewed by science writer, Melissae Fellet for KUSP.]

Historical ecology is the collection and synthesis of diverse historical data sources, done in order to make sense of past and present habitats.  Land managers sometimes use historical ecology to help guide science-based restoration and management decisions.  For examples, see Elkhorn Slough's projects or view impressive reports and presentations from the San Francisco Estuary Institute and the Southern California Coastal Water Research Project . You can also use historical ecology at home, to help you understand habitat patterns and trends in your yard and neighborhood.  While some organizations spend years collecting hundreds or thousands of historical sources to guide land management decisions, you can begin to understand your local landscape's past with just a few informative and easily accessible maps and aerials.  A few of our favorites are listed below, with links and hints.

If you live in the Elkhorn Slough region, we have also included some maps and aerials that you can use in Google Earth.  For more information about using these KMZ files below download this ReadMe file.

Historical Maps

  1. United State Geological Survey topographical maps, early 1900s.
    • To view or print these maps as pdf files visit
      • Click on "Historical Topographic Map Collection search" and search for the map you want.
      • To see maps for the Elkhorn Slough area, search for "Capitola" and "San Juan Bautista."
      • To see maps for Santa Cruz, search for "Capitola," "Santa Cruz," or "Los Gatos."
      • To see maps for Monterey and Salinas, simply search for "Monterey" or "Salinas."
    • Want to view historical USGS topos for the Elkhorn Slough region in Google Earth?  Elkhorn Slough staff have converted portions of the 1914 and 1917 images into kmz files.  Download the files below, and then open in Google Earth.
    • Interpreting the maps.  Some of the historical USGS maps include legends, others do not. 
      • To view the very simple legend from the 1914 and 1917 maps, click here.
      • To see a general legend for all USGS maps, click here.

  2. Vegetation Type Maps
    • What are they?  In the late 1920s and early 1930s the California Forest Experiment Station mapped, photographed, and sampled much of California's  vegetation. This detailed collection is now known as the Wieslander Vegetation Type Mapping (VTM) collection.  Teams at UC Berkeley and UC Davis, with funding from the US Forest Service and USDA CSREES, are digitizing the entire VTM collection for use in modern ecological and geospatial analysis.  
    • Want to view local VTM maps in Google Earth?  Elkhorn Slough staff have converted these maps into a series of kmz files, available here.  After downloading the file (11 MB), open it in Google Earth.
    • To view a legend of the map colors and some plant codes, click here.
    • For a complete list of the plant codes that appear in the VTM maps, download this Excel spreadsheet.
    • For other Wieslander Vegetation Type Mapping data (photos, original maps, sampling data) visit

  3. Maps of lakes between Castroville and Salinas
    • What are they?  In the early 1900s the Monterey County Surveyor, Lou Hare, mapped a series of lakes, marshes and sloughs that existed between Castroville and Salinas.  Those wetlands are highly modified today, but you can view their earlier configuration in Google Earth, by downloading and viewing the files below.
    • 1906_Hare_Lakes.kmz (10 MB) – This map appears to be very accurate, but omits the northern-most lakes, Merritt and Espinosa Lakes
    • 1919_Hare_Lakes.kmz (3 MB) – This map includes all of the lakes between the two north Monterey County cities, but is not nearly as accurate as the 1906 survey, above.  The railroad and other man-made structures line up well with today’s aerials, but the lakes themselves are offset by a quarter mile or more in some cases.  Nonetheless, this is a nice introduction to the approximate location of the now-drained lakes and their names back in the early 20th century.

Historical Aerials
Google Earth: To view historical aerial photos taken of the Elkhorn Slough area, download these files and then open in Google Earth.  Each file name begins with the year the aerials were taken (1937, 1949, 1956, 1966, 1980).

  1. 1937_Elkhorn_Aerials.kmz (25 MB)
  2. 1949_Elkhorn_Aerials.kmz (25 MB)
  3. 1956_Elkhorn_Aerials.kmz (21 MB)
  4. 1966_Elkhorn_Aerials.kmz (11 MB)
  5. 1980_Elkhorn_Aerials.kmz (12 MB)

To see individual images of these aerials and many more from other years and other Monterey Bay areas, visit the UCSC Library's Digital Collections.

Other Sources

  1. If you love old maps, and would like to view some of the earliest ones available for our region, check out the Mexican land grant maps.  These simple but beautiful sketch maps ('diseños') were created in the early 1800s (1820s-1840s), drawn by grantees as part of the granting process. Maps often include at least a few clues to past habitats - ponds, streams, trees, etc.
  2. If you like text more than maps, try a historical newspaper search:  Select "California" from the dropdown menu at the top, and then type in local place names in the search box.  Try a few different names to make the most of this source.  For example, a search for "Elkhorn Slough" brings up nine stories, written between 1898 and 1910; on the other hand, "Moss Landing" brings up an impressive 1383 hits.


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This site is maintained by the Elkhorn Slough Foundation in partnership with the Elkhorn Slough National Estuarine Research Reserve