Yerba Buena Chapter
1033 Noe Street
San Francisco, CA 94114
18 January 1999
Joan Ryan
San Francisco Public Utilities Commission
1212 Market Street, 2nd Floor
San Francisco, CA 94102
Re: Lake Merced 1998 Baseline Natural Resources Inventory, Draft Report
Dear Ms. Ryan:
Thank you for the opportunity to review this draft report.
We are appreciative of the PUC efforts to respond to community interest in raising the water level of Lake Merced. It is therefore with some regret that we must inform you that this document in no way provides "a baseline of the natural resource conditions at Lake Merced for future use in determining what impacts raising Lake water levels will have on Lake biota" (italics in original, transmittal letter from BEn Swann of Camp Dresser & McKee to Joan Ryan, 30 October 1998).
According to my dictionary, a baseline serves as a "base for measurement or comparison." A baseline must be well-defined and delineated; in baseball, the playing field is marked in bright chalk against the grass. The "baseline" provided here is extremely indistinct and will be of little use in future efforts to detect change. Three types of information are provided: qualitative descriptions of plant communities, a species list of plants found around the lake, and maps of vegetation interpreted from aerial photos. As baseline information, only the maps are useful; the spatial extent of current plant communities is quantifiable and readily measured against future aerial photos. In a dire hypothetical future, Lake Merced could lose 90% of its native plant species diversity and yet this loss would remain undetected if we relied on aerial photos.
Species lists provide a very rough measure of diversity. Rapid declines in abundance of even common species would not be detected by this method unless it became locally extinct -- that is, it could not be detected at any station around the lake. This hardly provides a meaningful measure of ecological health or response to lake level change. Nevertheless, species lists, when complete, are useful tools. The species list provided in the draft report is not complete. When generating a species list, it is essential to continue surveys until the number of new species identified -- ones not seen in any previous visits -- declines to almost zero. After three visits in late May and early June, the consultants had not encountered at least 5 native species that I had found during a single casual visit the previous year. They also did not identify many species beyond the genus level. The species list is therefore not anywhere close to being complete, and hence does not provide a baseline for future investigators interested in this very rough measure of the lake's natural resources.
In sum, this document does not provide "the necessary information for a recommended target lake level range," a primary objective listed in your transmittal letter of 15 December 1998. Indeed, there was no information provided in the vegetation section that was correlated with current or anticipated lake levels; a single reference to a previous report suggested that vegetation "changes do not correlate in an obvious way with lake levels."
These critical comments do not lessen our enthusiasm for a successful resolution to declines in the health and vigor of Lake Merced's terrestrial and aquatic resources. This document, though, does not achieve its objective of developing a baseline inventory of Lake Merced's natural resources. It also does not provide any information that will enable the community to evaluate proposals to raise lake levels.
Sincerely,
Pete Holloran
President
cc: San Francisco Recreation and Park Department, Natural Areas Program
