Standing near the intersection of Transverse Drive and Middle Drive West in Golden Gate Park, looking downhill towards Elk Glen Lake, I am surrounded by urban forest, no hint of the city in sight. The air is warm and smells pungent today, like a forest should! A red-tailed hawk is circling overhead. Tall, jagged Monterey cypresses, feathery Eucalyptus and top-loaded Monterey pines stand out against the sky. These are the “big three,” the trees that have provided the skeletal structure for this miraculous urban forest since it was established in this unlikely location in the nineteenth century. Many of the grand, old original trees remain, although nearing the end of life. The old Monterey pines (particularly susceptible to pine pitch canker) are going first.
The job of caring for, and renewing, this remarkable urban forest requires special knowledge, experience and dedication. We are lucky to have a crew of urban foresters in the park who fit this bill! In front of me, in the foreground (pictured above), is a new forest “plantation,” being managed by the forestry division in the park. To the untrained eye this baby forest might not look like much, but with a bit of squinting and imagination it’s not too difficult to envision what it will look like in fifty years or so, when the trees have grown in, adapted to local growing conditions and are properly thinned out.
The techniques used by the forestry division today in Golden Gate Park have evolved in many ways since William Hammond Hall’s experiments with growing trees on these sand dunes. But the basic approach that he adopted, through trial and error, has stood the test of time. Like in the nineteenth century, growing conditions are harsh, with challenging soil and strong, salty winds blowing off the ocean. Some types of trees do better than others in these conditions. As Hall demonstrated, it is wise to build on successes and learn from experience.
Although some basic conditions remain the same, managing a 150-year-old forest is different from planting one from scratch. When a large old tree dies in this forest today, it not only creates a gap that must be filled in, but its absence affects all the trees around it, which have grown accustomed to its presence. Often nearby trees will also weaken or fail without the support or shelter afforded by the missing tree. So forest management involves assessment of the condition of standing trees, as well as fallen ones. Sometimes weakened old trees must be removed for public safely before they fall down on their own and this may create sufficient room for reforestation. Areas selected for new forest plantations must be large enough to give young trees the sun and water they need without too much competition from older trees. But shelter is also important, as wind is a harsh environmental factor in this park. Planting new sapplings thickly, sheltering them from the wind and salt air by surrounding them with shrubby thickets, then thinning the plantations once they are established yields the desired result. But the process takes a long time and requires a lot of patience.
William Hammond Hall accomplished a miracle of sorts when he started this urban forest on the sand dunes of the Outside Lands against the odds and in the face of expert opinions. Sometimes it may seem like those were the “good old days,” but don’t think he had an easy time of it! I recently read a report of the Board of Park Commissioners from 1886, entitled “The Development of Golden Gate Park, and Particularly The Management and Thinning of Its Forest Tree Plantations,” which was clearly aimed at critics of the process used to establish the park’s forest, and a bid to win support (and funds!) to thin some overgrown plantations. The report includes a statement by Wm. Hammond Hall explaining that four times as many trees were planted as could grow to maturity, with the expectation that this would give young trees much needed support and protection from the elements, and that thinning would be a necessary part of the process. He also defended the planting of temporary wind breaks consisting of quick-growing and hardy evergreen trees, that would be removed, or thinned, once the tree plantations had matured. Frederick Law Olmsted wrote a letter, included in the report, supporting the methods Hall used to establish the park trees and affirming that “it was essential to the successful growth of the designed masses of foliage of the Golden Gate park, that its trees should be planted as closely as they were [and] . . . equally essential to the growth in a healthy way of such masses that, as the trees advance in size, their number shall be greatly reduced.” And John McLaren also weighed in with a letter calling for thinning stands of trees which, “unless they receive immediate attention . . . will be past recovery.”
So it seems that questions regarding the management of trees in Golden Gate Park are time-honored and perhaps inevitable. But as we take up these questions, we should beware of missing the forest for the trees!