Spurred by a U.S. senator determined to reverse congressional action from four decades ago, Point Reyes National Seashore officials are compiling a voluminous environmental impact statement on whether an oyster farm or official wilderness should occupy Drakes Estero.

The costly undertaking isn't without public appeal. While fewer than 200 comments were received on Grand Canyon National Park's mule rides, more than 4,000 comments were fielded by Point Reyes officials on whether Drakes Bay Oyster Co. should have its lease expire in 2012, as Congress directed in 1976, with the estero then being designated official wilderness.

That would have been the case if not for Sen. Dianne Feinstein, who in 2009 attached a rider to an appropriations bill giving Interior Secretary Ken Salazar the authority, but not a mandate, to extend the operation's lease another 10 years. With that nudging from the California Democrat, the Interior secretary saw that the Park Service conduct a full-blown EIS on the question of extending the lease, something it did not have to do.

An opinion from the Interior Department's solicitor in 2004 made it clear that the oyster farm would be incompatible with a wilderness designation. In that opinion, the solicitor's staff said "the Park Service clearly has the authority to terminate the Reservation and to direct (the oyster company) to vacate the property on which it operates," and that "(R)emoval of (the oyster company) from the Point Reyes National Seashore property and its oyster farming from the Estero, would allow the Service to begin the conversion of the area to wilderness status, which directive Congress charged the Park Service to accomplish."

Sen. Feinstein's pressure, however, gave the Interior Department and the Park Service the opportunity to officially examine the impacts of the oyster farm and hear what the public thought of it.

“It’s been debated in the press, it’s been debated in many forums, but this is actually the first time the public’s had an opportunity to weigh-in in a formal compliance process," said Brannon Ketcham, the park's hydrologist.

Along with examining water quality issues and biological impacts on the estero by the oyster operation, part of the environmental review, Mr. Ketcham said, will include revisiting the history behind the oyster farm's lease.

That history dates to November 1972 when Charles Johnson, owner of the Johnson Oyster Co., sold the 5 acres on the shores of Drakes Estero on which his processing facility sat, to the Interior Department for $79,200, with the understanding that he, or any successors to his company, could maintain operations for 40 years, or until November 30, 2012.

Four years later Congress passed the Point Reyes Wilderness Act, which directed the Park Service to manage the estero as official wilderness once the 40-year period was up. Since then, the oyster operation was purchased by the Lunny family, which has lived in the area for three generations.

The estero is a biologically rich and important landscape for wildlife, according to a Park Service fact sheet on the estero.

Drakes Estero is one of the most ecologically pristine estuaries in California and the only coastal waters in the California that are in the National Wilderness Preservation System. Biotically, the estuary is exceptional:

• Extensive eelgrass beds support rare and specially protected species

• Reduced presence of non-native species: recent surveys show that many invasive species are only found where mariculture and oyster racks occur, but not in Limantour Estero (on the eastern end of the estero).

• One of the largest harbor seal populations in California with numbers surpassing 1800

• Identified as significant area for the US Shorebird Conservation Plan: 86 Species of birds recorded in 2004, including Osprey and Black Brant.

• USFWS recognizes 18 species of concern, including Red-legged frog, Western Snowy Plover, Brown Pelican, Peregrine Falcon, and Marbled Murrelet.

• Recent fish survey identified over 30 species of fish, including rare and endangered species such as coho salmon, steelhead trout and three-spined stickleback.

• Rare plants occur along the shoreline of the estuary.

But controversy has dogged the Park Service's handling of the oyster company operations. The National Research Council was highly critical of a Park Service report that outlined the oyster operation's impacts to the estero. That report, the research council said in May 2009, was "selectively" manipulated in several areas, and inconclusive overall.

"...the adverse or beneficial effects of oyster farming cannot be fully understood given the existing data and analyses," stated a news release from the council, which is an arm of the National Academies that also includes the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. "Furthermore, the National Park Service report, 'Drakes Estero: A Sheltered Wilderness Estuary,' in some instances selectively presented, over-interpreted, or misrepresented the available scientific information on DBOC (Drakes Bay Oyster Co.) operations by exaggerating the negative and overlooking potentially beneficial effects."

A study of shellfish mariculture in Drakes Estero compiled by the Ocean Studies Board of the National Academy of Sciences pointed to both benefits and impacts of the oyster farm. That 2009 study pointed out that the native Olympia oysters were lost to over-harvesting in the mid-1800s and that while the Pacific oyster now being farmed "is not a direct replacement of the native populations of the Olympia oyster, it may be viewed as providing similar biogeochemical functions and ecological resilience."

But the study also noted that the lack of eelgrass below the suspended racks of oysters "represents a small-scale and localized impact on the biogenic habitat." Additionally, "(N)umerous boat propeller scars in the eelgrass beds, partially affecting a total area of about 50 acres, are also evident and attributable to oyster culturists because they are the only ones allowed to use motorized vessels in the estero.

"Nevertheless, the total percentage of eelgrass area lost (1%) or partially degraded by propeller scars (7%) and thus attributable to oyster mariculture represents about 8% of all eelgrass habitat in Drakes Estero as of 2007."

The estero is important habitat for harbor seals, according to the study, which notes that it supports "about 20 percent of the mainland California population."

Along with considering the findings of those studies, Mr. Ketcham said the seashore staff also would look into a wide-range of issues raised during the public comment period, including the socio-economic impacts of the oyster operation.

Park Service officials system-wide state that public comments should not be construed as votes that they have to follow. Nevertheless, according to an analysis of the public comments by the National Parks Conservation Association, a 3-1 majority opposes an extension of the oyster company's lease.

Point Reyes officials hope to have a draft EIS ready for public review late this summer, with a final EIS in the spring of 2012 with a record of decision signed before the current lease expires.