Trees Cut Down In Marin Headlands To Help Rare Butterfly

Grove of non-native trees on Hawk Hill come down in the Marin Headlands

Chainsaws are buzzing high on Hawk Hill in the Marin Headlands as workers remove a grove of about 200 non-native trees to help preserve rare butterflies.

National Park Service officials say they are cutting down the non-native trees across six acres to create more habitat for the endangered mission blue butterfly. Work started last week and will continue into next month.

The branches and limbs of the Monterey pines, cypresses and tea trees are being fed into a chipper to be used in the Presidio in San Francisco for mulch, while the trunks are being sent to a co-generation plant.

Rather than dragging the trunks and causing damage to the natural understory of ferns, scrub and brush, cranes grab them and put them into a neat, stacked pile.

Removal of the trees is part of “Project Headlands,” an $8.7 million federal effort to improve access for motorists, bicyclists, pedestrians and public transit in the Marin Headlands. As part of that work, the National Park Service must “mitigate” for the impact of its roadwork — such as find ways to improve wildlife habitat.

One step the agency is taking is to cut down the trees in order to plant lupine that will create mission blue butterfly habitat.

“We expect a lot of natural seed to come in here, but we will also plant native plants that are grown in the Marin Headlands nursery,” said Caroline Christman, project coordinator for the Golden Gate Parks Conservancy, as a Marin County Arborists’ wood chipper churned in the background.

Despite the grove of trees, native vegetation has fared well over the years.

“There are a lot of natives that are still here, the ferns and the coyote brush,” said Alison Forrestel, acting vegetation ecologist for the Golden Gate National Recreation Area. “There are also populations of the mission blue butterflies on either side of the trees.”

Once the trees are gone, a five-year vegetation and invasive species control plan will follow. The area is now closed for the work, but the public will be allowed back into the site once the tree work is done.

“The trails that were here before still will be here,” Christman said.

The forest was relatively new and did not exist before 1970 beyond a handful of trees, because the military kept the trees in check, not wanting a visual impairment that might block views of the Pacific Ocean.

It’s not known exactly how the trees arrived. One theory is that they came with soil brought from nearby Kirby Cove to cover concrete bunkers built into the hillside by the military. Pines were planted in Kirby Cove in the early part of the 20th Century and the soil may have had seeds in it.

The removal work is being done now so that migrating and nesting birds are not affected, but there may be some changes for bird watchers once the trees are gone.

Hawk Hill, which sits 900 feet above the Golden Gate, is a favorite spot among birders to observe migrating hawks, eagles, falcons and other birds of prey as they glide by. The raptors occasionally rested in the grove of trees, as did other migratory birds.

An environmental impact report by the park service said the tree removal “would result in a loss of birding opportunities for unusual coniferous migratory birds that may be attracted to that area in the spring and fall seasons. Tree removal would also change the character of the Golden Gate Raptor Observatory’s long-term raptor monitoring site.”

But park officials noted the raptors never nested in the trees, and while bids such as pygmy nuthatches did, they can find other habitat nearby.

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