Vote looms on San Bruno Mountain development

The Brisbane City Council will vote Tuesday evening on a hotly contested land development proposal that has pitted residents and environmentalists against government agencies. The debate centers on whether a plan to build 71 homes on the Northeast Ridge of San Bruno Mountain would threaten the survival of an endangered butterfly species.

Testimony at previous Council meetings, on Jan. 19 and Feb. 1, has painted two very different views of the impact development will have on the mountain. Yet both sides profess to have the best interests of the butterflies at heart, and both argue their claims are backed by science. 

A precarious balance

What's at stake is a delicate balance of species. Each spring, after flying to hilltops to mate, female Callippe silverspot butterflies lay their eggs near a rare violet plant called Johnny Jump Up. Without the violets, the caterpillars can’t survive. And the plants are finicky, only growing amidst native grasses.

“If you’ve ever been to the rainforest… that’s what you have on San Bruno Mountain, but on a tiny, tiny scale,” said Thomas Wang, a professor of environmental horticulture and floristry at City College of San Francisco, at the Jan. 19 meeting. “The grasslands, these butterflies -- this is the unique stuff that’s nowhere else in the world,” Wang said.

Once common, Callippe silverspots are now found only on San Bruno Mountain and in a few other places around the Bay Area.

The threat of construction

A coalition of residents and environmentalists has been working for years to stop construction projects on San Bruno Mountain. Regarding the current proposal, they fear the new homes won’t leave a big enough corridor for butterflies to travel from the Northeast Ridge to other parts of the mountain. Without a corridor, populations can’t mix. Scientists say isolating a population decreases its genetic diversity, and thus its ability to survive.

Terry O'Connell is a longtime Brisbane resident and a board member of the grassroots conservation group San Bruno Mountain Watch.

“Who are you going to listen to?" she asked City Council members at the Feb. 1 meeting. “Federal bureaucrats who have to be sued to protect species? Or are you going to listen to your neighbors, your constituents, people you see at the grocery store, the people of Brisbane who have spoken in one voice?” 

A bigger concern

The federal agency O'Connell is referring to is the U.S. Fish and Wildlife Service, which is in charge of protecting endangered species. It, along with San Mateo County and the city of Brisbane, negotiated with developer Brookfield Homes for nearly a decade before coming up with the current proposal.

In May, Fish and Wildlife gave its okay to the plan, which includes permission for incidental "take," or killing, of Callippe silverspots. The county signed off in October, sending the proposal to Brisbane for the final say.

County and federal officials, as well as a conservation biologist who worked on the mountain for 13 years, favor the plan because it raises money for habitat management -- a $4 million endowment, to be precise, funded by developer Brookfield Homes. Owners of the new homes would pay an additional $800 per year in habitat fees.

“To me, having struggled to manage that mountain with the existing budget, it’s a no brainer,” said Patrick Kobernus, a former environmental consultant for TRA Environmental Sciences, Inc., the firm contracted by the County until 2007 to handle habitat management on San Bruno Mountain.

Kobernus says the butterflies face bigger threats than that posed by the new construction, which would cover 20 acres of land. The mountain's 2,800 acres of conserved habitat are changing. Non-native plants from urban gardens are invading grassland territory. In addition, all over California, native coastal scrub is expanding its range. In San Bruno Mountain’s case, this means moving into the grassland habitat.

These are serious issues that will require money and attention, Kobernus says. He throws out numbers: 1,250 acres of current grassland, compared to 1,400 acres in 1982, compared to 1,800 in the 1930s -- a loss of at least five acres a year.

Hand picking and herbicide treatments have curbed invasions of non-native plants such as gorse, French broom and eucalyptus, he said. But the county needs more cash for cattle grazing and controlled fires if it wants to keep the grassland it has, let alone reverse the trend.

Weighing the options

Ken McIntire is executive director of San Bruno Mountain Watch, which has been highly critical of Kobernus’ work. McIntire argues the habitat money comes at too high a price for the butterflies. An environmental impact report for the project dates back to 1982, and McIntire wants it redone.

If new homes are built, butterflies will have to navigate gardens and four- and six-lane roads to traverse the mountain. McIntire points to a 1982 study by TRA, in which researchers captured, marked and released butterflies. They concluded roads and housing are at least partial barriers for butterflies.

Kobernus counters that Callippe silverspots are strong fliers. After all, gusty winds blow hard on San Bruno Mountain and the butterflies still find their mates on exposed hilltops.

Kobernus refers to butterfly surveys conducted after 1982. Instead of capturing them, surveyors in 2005 and 2006 walked the mountain looking for butterflies, and noted the date, time and location each time they saw one. As Kobernus wrote in a Jan. 26 letter to the City Council, those surveys recorded several instances of butterflies crossing the road.

Inconclusive science

Those observations are valid, says Travis Longcore, a professor of geography at University of Southern California. But they’re not definitive. They don’t indicate whether the butterfly crossings are frequent or rare. And they say nothing about how a construction project might change things.

On the other hand, Longcore says, concerns about the growth of invasive plant species in Callippe silverspot's habitat are real. In January, he and Patrick Kobernus co-authored a scientific paper showing a correlation between a decrease in butterfly sightings and the spread of native coastal scrub. When the scrub takes over grasslands, butterfly habitat disappears.

The message of the paper: native plants can threaten the species you care about. “Sometimes you have to manage your property,” Longcore said.

The Brisbane City Council will meet again on Tuesday, Feb. 16 at 7:30 p.m. to vote on the development proposal. 

Click on the audio player above to hear voices from the Feb. 1 Brisbane City Council meeting.