Presidio Plan Tries to Balance Needs of New, Old Forests

By Erica Gies

Seen from the air, or on a map, the Presidio appears to be one of San Francisco's largest green spaces. As it turns out, the park is that and much more - the area is officially designated as a national park and historic district. It's home to some of the oldest buildings in the City and some of the newest non-profit groups. It has a bowling alley and is one of the only suitable habitats in San Francisco for the preservation of the California quail.

The Presidio is subject to intensely competing mandates - to preserve a centuries-old military past and protect and restore an even older indigenous eco-system, while simultaneously generating sufficient revenues to pay for itself. How best to balance these different interests is largely determined by the park's triumvirate of managers: the National Park Service (NPS); Presidio Trust, a public-private government agency; and the Golden Gate National Recreation Area (GGNRA).

"In many ways, natural parks are museums preserving natural resources and keeping them for future generations," said Betty Young, Golden Gate National Recreation Area (GGNRA) director of nurseries, which grows native plants for Presidio restoration projects. "The mission of the Park Service is to preserve natural and cultural resources. The historic forest on the Presidio is a cultural resource. Those two goals, preserving the natural and the cultural, have to somehow work together."

Perhaps no one understands this balancing act better than Terri Thomas, director of park resources for the Presidio Trust. She's working to restore both the Presidio's native plant communities, including many endangered species, as well as protect the aging non-native trees planted by the U.S. Army.

The Army planted the non-native eucalyptus, Monterey pine, and Monterey cypress forests to create windbreaks, establish boundaries between different areas of the fort and to make the land more appealing to the soldiers stationed there. Many San Franciscans still find the trees attractive - and emblematic of the Presidio.

However, the non-native trees, while providing habitat for Cooper's hawks, woodpeckers and some of the other more than 200 birds who migrate through the park, also inhibit the growth of indigenous plants protected by the Federal Endangered Species Act.

"The Presidio had diverse native vegetation and still does," Thomas said. "It's very valuable to restore remnants of this ancient landscape, very fragile remnants that include endangered species, rare species, rare habitats."

Prior to being settled by European explorers, most of the Presidio - and in fact, most of San Francisco - was sand dunes, populated with low-growing plants. These species adapted to thrive in full sunlight and do not do well under the shady canopies of the non-native trees.

The historic forest planted by the Army is old and deteriorating. As individual trees die, the Historic District charter requires they be replaced. But in some park areas, managers are considering substituting the historic species with older, indigenous vegetation.

In consultation with other stakeholders, including the U.S. Fish & Wildlife Service, California Native Plant Society (CNPS) and the Audubon Society, Thomas and her team drew up a map of zones to be managed differently.

For example, there are several stands of trees in rows along streets that are considered to be historically significant. Because these trees are near buildings and were planted in a linear, unnatural fashion, they have a very specific look. When these trees die, they will be replaced with the same species in the same rows.

In other areas, where the Army planted trees more haphazardly, "the value of the forest is probably as a dark green backdrop to other things," Thomas said. "In those cases, there's more flexibility. You can have multiple strata of trees that's better wildlife habitat."

One possibility is a different type of eucalyptus that doesn't have as dense a shade canopy and leaf litter, like the current blue gums.

Another species under consideration is the coastal live oak, which is native to the Presidio. It was originally found only along the riparian corridors bordering Lobos Creek and Mountain Lake. Thomas and her crew have planted test patches of the oak to determine how it will do in other areas and how other native plants will fare under its canopy.

Other native-to-the-Presidio trees that might be more widely planted if test patches go well include California buckeye, coffee berry and toyon, which are small, grow well under other trees and have berries wildlife finds tasty.

Another zone that provides a great deal of potential "new" area for natives has not been designated historic because the Army did not value it: dumps.

"The Army thought that every canyon over a bluff was a place to throw garbage," Young said. "They thought they'd just cap them and plant grass. The Trust is actually removing the landfills and restoring those areas back to the habitat that was there before. And that's a significant restoration because those sites were large."

According to Thomas, "We're doing a dramatic one right now on the coastal bluff. We took out the landfill and now it looks like the Grand Canyon. These places were just nothing and we're turning them into pretty cool stuff. The first one we did was a parking lot and now it's got three different kinds of habitat on it."

Pinky Kushner, who's head of the Sierra Club's open space committee, was pleased with the results.

"When one walks along the walkway, the place hums with life: insects and birds and butterflies of all sorts," she said.

In spite of the Trust's success in increasing native habitat, some stakeholders are frustrated by the restrictions imposed by the need for historic forest preservation.

Peter Brastow, rare plants co-chair for CNPS' Yerba Buena Chapter, says that his group applauds the Trust's work on ecological restoration. However, he's concerned about how the historical mandate will impact the ongoing success of native plants and animals.

"The historic forest is a planted forest 120 years old. The indigenous animals and plants are thousands, maybe millions of years old," Brastow said. "The Presidio is not just something that happened. It's something that's going to happen in the future. What's truly logical in terms of managing land for the future? Keeping part of this forest frozen in time or adapting to the idea that this thing has to evolve into the future? The most sustainable effort is to bring back the processes that sustain biological life so they'll ultimately work for themselves."

Some of the Presidio's native critters would benefit from more native habitat, including the monarch butterfly, California slender salamander and gray fox.

California quail used to flourish among the silver dune lupine, mock heather and coyote bush. Due partially to the increase in non-native plants, the population declined significantly in the '80s and today there are only 20 left in the Presidio.

According to Alan Hopkins, director of the Save the Quail campaign for the Golden Gate Audubon Society, a lot of non-native plant species have taken over, including ice plant, various ivy species and all of the ground cover. 

"There are a lot more predators than before: cats, raccoons, ravens, crows, jays. They are getting squeezed at both ends," he said.

Hopkins and others at the Audubon Society took their concerns to the Presidio Trust, and managers there prioritized quail habitat for native plant restoration.

"Native plant restoration is keeping them going and keeping them alive," Hopkins said.

In 100 years, Thomas would hope to see "native diversity maximized, wildlife enjoying the mosaic of habitats, creeks restored, and the public enjoying and being educated by that diversity and abundance."

For more information about enhancing and expanding the native habitat in the Presidio and at Crissy Field, call (415) 561-3034, ext. 3445.

Erica Gies is a writer with the Neighborhood Environmental Newswire.