| "Historical ecology plays a real key part in planning for future restoration and habitat management." | |
| Eric Van Dyke, Geographical Ecologist with Elkhorn Slough National Estuarine Research Reserve |
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The idea behind historical ecology is that, in order to decide today how to restore a degraded ecosystem, one must study and thoroughly understand its history to determine why and how its habitat was lost. A California National Estuarine Research Reserve is undertaking a historical ecology project to help plan for and set restoration goals.
"There's a misunderstanding among the restoration community that there's an ideal point in history to use as a reference point for restoring a site," says Eric Van Dyke, geographical ecologist with Elkhorn Slough National Estuarine Research Reserve near Monterey. "There needs to be an understanding that there is a range of variability that a system will naturally undergo. What we have to do is separate out what naturally transpired and what was caused as a result of humans."
Van Dyke and other Elkhorn Slough staff members are using a variety of historical sources to construct a geographic information system (GIS) of past environments in the watershed to determine the causes that underlie changes in habitat structures.
Big Changes
Habitat at the reserve is "changing rapidly," says Van Dyke. "Marsh vegetation is being lost, and substantial areas are changing from vegetation to mudflats or open water.
"The question asked was, ‘why?'"
To get a long-term perspective on what was happening, the "historic record would have to be looked at."
Hypothesis Testing
The reserve hired Van Dyke to help conduct a historical ecology project. Van Dyke explains that historical ecology is a relatively new field of ecological study that "is really based on science."
"It's not social science; it's science looking at past evidence," he says. "You're still following the scientific method of hypothesis testing; you're just not proving it using real-time lab or fieldwork.
In beginning the reserve's project, Van Dyke reviewed work using applied historical ecology done by the U.S. Geological Survey and the San Francisco Estuary Institute.
Backwards in Time
The reserve staff members worked backwards in time, beginning with current digital orthophotographs and working their way backwards in decadal increments while collecting a set of reference points.
The Staff "obtained, converted to digital format, georectified, mosaiced, and interpreted 26 historic maps and charts dating from 1853 to 1925, and 13 aerial photograph flights taken between 1931 and 2003," says Van Dyke.
Other sources of evidence include surveys, historic T-sheets (topographic maps), written documents, such as local newspaper accounts, and even interviews with descendants of families who lived in the area in the 1800s.
Detailed metadata were collected for each data layer.
Towards the Future
Doing the historical ecology project has changed some long-held assumptions about the impacts of old dredging and channel projects that had occurred on the reserve.
In addition, the reserve has received funding to conduct an extensive tidal wetland planning project, Van Dyke says. The result will be a management plan that "understands the changes we're dealing with," which will help improve the effectiveness of reserve habitat restoration projects.
"Historical ecology plays a real key part in planning for future restoration and habitat management," Van Dyke says.
He adds, "I would recommend it. I can't imagine any of the wetlands systems not being informed by historic evidence."
For more information on ElkhornSlough National Estuarine Research Reserve's historical ecology project, contact Eric Van Dyke at (831) 728-2822, or vandyke@elkhornslough.org.
Additional Information on Historical Ecology
www.elkhornslough.org/tidalwetland/downloads/VanDykeWasson2005.pdf, April 2005 Estuaries article on Elkhorn Slough National Estuarine Research Reserve's historical ecology project.
www.sfei.org/HEP, Web site of San Francisco Estuary Institute's historical ecology project.
www.fort.usgs.gov/resources/spotlight/place/place_exhistory.asp, U.S. Geological Survey's information on applied historical ecology.
www.islandpress.org/books/detail.html?&SKU=1-55963-746-3, Island Press Web site featuring The Historical Ecology Handbook: A Restorationist's Guide to Reference Ecosystems.
http://coastalexplorer.imcwv.com/viewer.aspx?X=1179&Y=1430, Coastal Explorer, the National Oceanic and Atmospheric Administration's U.S. Coast Survey's on-line map resource. A "T-Sheet User Guide: Application of the Historical U.S. Coast Survey Maps to Environmental Management in the San Francisco Bay Area" is available at www.sfei.org/HEP/reports/T_sheet_user_guide_SFEI_highres.pdf.
