An answer to whether or not Drake’s Bay Oyster Company is harming the environment remains elusive, as the National Academy of Sciences last week judged evidence in the Draft Environmental Impact Statement (DEIS) issued by the National Park Service to be insufficient.

Of 14 possible “impact” categories, the DEIS alleged the oyster farm caused major negative impacts in two—sound and wilderness. The authors used sound measurements from police boats and highway construction equipment as stand-ins for the actual sounds of the oyster farm’s motorboats and oyster tumbler. Seashore scientists contend that this disturbance negatively impacts the estero’s harbor seal population, while also detracting from the estero’s “wilderness” 
experience.

But the Academy’s National Research Council (NRC) has declared that there isn’t enough data in the park’s environmental review to draw conclusions of harm. Committee chairman Thomas Malone told the San Francisco Chronicle last week “There were (in several cases) other conclusions they could have reached given the information at hand.”

During a public meeting of the NRC in July, several members expressed confusion over why each of the DEIS’s proposed alternatives included alterations to the farm’s activities. According to Environmental Protection Act laws, all studies must compare their findings to a baseline. Among the proposed alternatives, most EIS’s would contain a “business as usual” option, against which any planned changes could be measured.

A panel of scientists had already concluded in 2009 that the park service had made errors in their research and had presented information selectively. Another report, released last year by the Interior Department’s Office of the Solicitor, called the park’s work biased, improper and mistake-ridden.

Dr. Malone has said that while the DEIS’s conclusions were reasonable, they could not be proved without further studies.

Conservation groups such as the Sierra Club and the Marin Audubon Society have long alleged harm to the environment by the oyster farm, and have pointed to a July enforcement order by the California Coastal Commission as evidence that the oyster company has violated seal protection areas and left marine debris in Drakes Estero. But oysterman Kevin Lunny sees the NRC report as a victory.

Mr. Lunny could not be reached for comment, but he told the Chronicle last week: “For more than six years, the National Park Service has been telling the people of West Marin that our oyster farm and our workers were harming harbor seals, choking eelgrass and otherwise doing great harm to the environment. We now know that NPS just plain made it up to drive us out of business.”

Corey Goodman, the scientist who has been the park service’s chief detractor in the ongoing debate, said that it was gratifying to see the Academy confirm “for the second time” what he has been insisting upon since 2007.

“The National Park Service does not have the data to claim, as they have done over and over again, that the oyster farm has a negative environmental impact on Drake’s Estero,” Dr. Goodman said. “The community and their elected officials need to ask some tough questions.”

He said in a statement that these questions included why the park was obsessed with “claiming scientific data where no such data exists and harm where no harm exists.”

“The accountability for spending millions of dollars of taxpayer money rests at the top,” he said. “It is time to ask why NPS leadership has been so fixated on removing the oyster farm from Drakes Estero that they have allowed their agency to misuse science.”

This May, the NRC committee was tasked with evaluating the effects of issuing a Special Use Permit that would allow 10 more years of commercial mariculture in Drakes Estero. As the farm is now widely considered the single “non-conforming use” in the potential wilderness area, its elimination would result in a transfer to full wilderness status — a shift many have fought hard for, but which certain supporters of agriculture in the seashore have heralded as the beginning of the end for food production there.

The purpose of the committee’s report was to assess the scientific information, analysis and conclusions in the DEIS, and to decide whether or not a peer review conducted by Atkins North America was fundamentally sound and materially sufficient. The committee did not perform an independent evaluation of the environmental impacts of the proposed alternatives.

The DEIS defined adverse impacts to the estero as minor, moderate or major, in order to “describe impacts based on their intensity or magnitude,” the NRC report said. However, it found it “noteworthy” that only one category of beneficial impact was used, eliminating the possibility of distinguishing between effects that ranged from minor to major beneficial, as was done with adverse effects.

For most of the eight resource categories that the committee was asked to review, it concluded that the DEIS did not define impact intensity levels that could be clearly related to the magnitude of the effect, thus making it difficult to determine both the comparative impact of the different alternatives, and the relative levels of impact across resource categories.

For example, the report said that both the “moderate” and “major” intensity definitions for wildlife and wildlife habitat included the mention of impacts on “individuals,” which the committee took issue with. Presumably, the death of a single unspecified organism due to the flipping of oyster bags did not constitute the committee’s idea of a major ecological impact.

Also, the committee assessed the strength of the available scientific information in order to determine its uncertainty levels, which it said would give decision-makers a better understanding of the range of potential impacts for each action alternative. Of the eight resource categories, the committee judged that the projected impact levels of seven had moderate to high levels of uncertainty. For many of these, the committee said researchers could have reached the conclusion of lower level of intensity.

Suggesting “high priority” revisions, the committee said the DEIS should use definitions of impact intensities that provided a better magnitude scale for both adverse and beneficial effects, and which included a category for negligible impact. They also said the DEIS should provide a discussion of the levels of uncertainty for the impact intensities. A future assessment should also include additional mitigation options as possible permit conditions for the action alternatives to reduce impacts—for example, to discontinue the culture of Manila clams, a nonindigenous species.

The committee stressed that the impacts of many of the oyster company’s practices, such as boat use, culture techniques, marine debris and soundscape disturbance, could potentially be reduced by “appropriate mitigation measures.”

This echoes Marine Mammal Commission head Tim Ragen’s earlier calls for the adoption of an adaptive management plan for the estero, and Mr. Lunny’s repeated insistence that the farm does not cause intrinsic harm.

Park officials could not say exactly how a revised DEIS would be produced, or whether or not any new data would be collected. Melanie Gunn, the outreach coordinator for the DEIS, said the park was still in the process of reviewing the NRC’s suggestions.

“We appreciate the work of the Academy and look forward to reviewing the National Research Council Report,” Ms. Gunn said. “We welcome the input and will consider the recommendations of this report, along with the other scientific reviews and more than 52,000 public comments, as we work to strengthen the final EIS.”