(Note: this post is part of the Infrastructural City Blogiscussion. Click here for mammoth’s introduction to this chapter)
In addition to Los Angeles’ Palm trees, Warren Techentin’s Tree Huggers Chapter briefly mentions that the most widely planted non-native trees in California were varieties of the Australian Eucalyptus, or as Techentin describes it, “the Eucalyptus Crusade in which thousands of acres of the trees were cultured from Australia and obsessively planted throughout the state.” In direct contrast to palm trees, Eucalyptus were imported and planted for practical ‘performative’ uses, such as windbreaks, firewood and shade. The century-plus legacy of these plantings is still evident throughout the City of San Francisco, where they can be found all over Golden Gate Park, the Presidio and just about everywhere else.
One of the most intriguing of these vegetated habitats is the Eucalyptus forest on Mount Sutro. Located nearly dead center in San Fransisco, the 80 acre forest was intentionally planted with Eucalyptus beginning on arbor day of 1886. The current Mount Sutro forest is a remnant of the more than 1,000 acres of planted Eucalyptus forest that once covered the western side of the city.
I used to live about a five-minute walk from this forest and subsequently spent a significant amount of time there. One of the most memorable features of the forest was how uninhabited it was by people. As most of the steep inclines on which the forest sits are on private land, its presence was not advertised, and thus it just wasn’t on people’s radar. There were no trail maps of the forest that I was aware of, which made it all the more fun. I went there to try to get lost. On pleasant days there would be thousands of people in nearby Golden Gate Park, but no one in the Sutro forest. In a twist of Olmstedian logic, I would climb up Mt Sutro, rather than go to Golden Gate Park to retreat from the intensity and crowds of the city.
For years the forest was largely left to itself, building a unique ecology composed of ruderal, invasive and native species that could coexist with the Eucalyptus.
The physical experience of being in this forest is fascinating and truly unique. The 100+ year Eucalyptus are now 100-200′ tall, forming a high airy canopy. The sheer size of the forest is a wisp, anthropogenic counterpoint to the region’s towering redwood forests. The light, textured shade that Eucalyptus trees provide is visually exquisite.
[image by flickr user JoeHague]
[species from Australia, Europe, Asia Minor and Coastal California brought together to work it out on their own. Image by flickr user tdanders]
Blankets of English Ivy envelope the lower halves of the Eucalyptus trunks, looking like something dreamed up by Dr. Seuss. Over 90 species of macro organisms have been recorded in the forest, including a large numbers of birds. The micro climate of the Sutro Forest (and San Francisco generally) is inherently dynamic due to its proximity to the ocean; a modified Mediterranean climate. The steep, protruding topography of Mt Sutro places the forest in the clouds, with daily occurrences of thick fog. One moment the sky is clear, the next its twenty degrees cooler and you can’t see more than 20 feet in front of you…a Costa Rica-like cloud forest:
The terraforming of these hills with Eucalyptus has inadvertently created a harvester of clouds. Like a massive net, tree foliage captures condensation that would otherwise pass by, rendering the microclimate considerably more wet (an additional 30%) and thus more vegetated than it probably ever was throughout its long pre-forested history. The growing forest has begot more forest. As historians have demonstrated, the native ecology of San Fransisco consisted of grasses, forbs and scattered shrubs, but was mostly bare, sandy and less than hospitable for urban living. It certainly was never forested. And similar to Mt. Sutro, Golden Gate Park was a much larger terraforming project – transforming large swaths of shifting sand dunes into an urbane botanical pleasure ground. Almost the entire surface of the bay area peninsula is fully constructed.
In the years since I left San Francisco, a lot of changes have occurred on Mt Sutro. A large area near the summit was cleared of Eucalyptus trees (evident in the closeup aerial above) and a meadow of native plants put in its place with the hopes of creating habitat for endangered butterflies. Proposals for thinning the trees have been debated and further selective replacement of the Eucalyptus forest have been proposed. Trails have been cleared and new ones created. Native plant societies are clashing with grass-roots organizations that hope to save the naturalized forest. Ironically, environmentalists are suddenly on the side of being destroyers of habitat. The services that the forest provides is being fiercely debated along with the ‘nature’ of its ecology.
At the time the Eucalyptus trees were planted, none of this was on anyone’s mind. The trees were planted strictly for the benefit of people – firewood, windbreaks, shade. No one knew that the trees would evolve into a unique, naturalized and self-sustaining forest that places it squarely in contemporary debates in urban ecology and forestry 120 years later. This includes issues we have discussed at length at this blog, and which mammoth covers in their introductory post for this chapter, including nativism, weighing the benefits and problems of weeds and invasives, implications of defining humans as an omnipresent continuous disturbance regime, classifying ecosystem services, etc.
Rather than provide my opinion on this one, I would like to direct you to a fascinating blog that can provide a stronger grounding in the specifics of the local ecology: Save Mount Sutro Forest. Obviously their title lets you know where they stand, but what I value about the site is its open dialogue on the issues (contrary views are encouraged and posted) and its rigorous pursuit, study, and investment in a locally specific ecology. By locally specific I don’t mean native, but rather a thorough observation of the unique collection of forces and interactions as embodied in the specificity of site. On their blog you can read about what species are found in the forest vs. surrounding habitats, find links to latest pertinent scientific studies and contrary viewpoints, debunk various myths that surround Eucalyptus and learn how long Eucalyptus live (the ones on Mount Sutro could continue on for another 300 years…and if you chop them down, they re-sprout from the trunk for up to nine years).
It’s this type of rigorous testing and exploration that might foresee a productive future for the Sutro Forest and lead to landscape as an ongoing foundational infrastructure.
(All unlabeled photographs are courtesy of Save the Sutro Forest’s Photo section)