People have mentioned the sounds of and in the forest before, but it was only when we joined a Soundwalk in the forest that we became so conscious of it. Recently, someone pointed us to an article about Soundscape Ecology, about the work of Bryan Pijanowski of Purdue University. From that article:

“The terms we’ve developed allow us to think through ecosystem processes and the way humans impact that. The terms we’ve developed are:

• Biophony – To be able to understand the biological voices that occur in the landscape
• Geophony – [Sounds from the geophysical environment], such as wind and water
• Anthrophony – The noise that humans make, which can be produced by a variety of instruments

If you put a microphone in the middle of an environment, you can record all those. You can record them for long periods of time. You can look at all aspects of the environment at any time of the day…”

Inside Sutro Forest, the tall trees and dense vegetation muffle the noise of the city. You don’t usually hear traffic sounds in most areas, even though it’s surrounded by streets and neighborhoods and on the Parnassus side, even a power-plant. Until even two years ago, the only “anthrophonic” sounds that pierced the forest were sirens — and, because it’s under some flight-paths from SFO airport, the occasional drone of airplanes. Now, in some areas, traffic sounds come in.

The main “biophonic” sound is — on a bright day — birdsong. Until the destruction of a lot of the understory, there was more of it than there is now, but it’s still audible.  On foggy days, there’s only the odd chirp. Where do we classify the rustle of birds in the undergrowth? There’s that, too.

Where do we classify the sounds of the trees themselves? There’s the soughing of the wind through the tops of the eucalyptus, the creaking and tapping of branches and twigs against each other. On really foggy days, there’s the patter of the forest’s internal rain on the leaves below; those days when it’s dry outside the forest and raining inside it where the trees precipitate the fog. That’s the cloud forest effect.

MANMADE SOUNDS UP, NATURAL SOUNDS DOWN

Coming soon to Sutro Forest?

This soundscape will be destroyed if the plan to cut down 5000 trees (and later, perhaps 35000 trees) goes through. This is what cutting the trees will do:

• In the initial stages, the “chilling sound of chainsaws in the forest” as one neighbor described it — or maybe even the rumble and crash of the brontosaurus.
• Then, a rise in the anthrophonic sounds of the city, already more audible than when we first set up this site two years ago… the rumble of traffic, the sounds of drums and music played loudly in the Golden Gate Park and in schools. There was a time when, inside the forest, there was no sight or sound of the city; it was a different world hidden in the heart of San Francisco. That’s less true today; in many places, gaps in the trees and removal of the blackberry has opened up the forest to views — and noise. Voices of people using the trail, barely heard now, will be more audible once the understory is torn out and the trees removed.
• A reduction in biophonic sounds. The birds delighted in the understory, the dead tree snags, the ivy growing around the trunks of the trees, providing nesting and foraging space. As this habitat is reduced, so also are the birdsounds.
• A change in the geophonic sounds. The wind will sound different, with 5,000 trees (or 35,000) fewer trees, with no understory to speak of. The tapping and creaking — who knows, once trees are spaced 30 feet apart?

Will it sound like a forest at all? Or just another hill in the middle of our city of hills?