Here we go again.

San Francisco’s cutting down more trees, as though its paltry tree cover – less than any other major city – needed further depleting. This time, 49 trees on Market Street are planned to be felled to make way for fancy new BART station entrances.

BART entrance with trees – Market St San Francisco. (Copyright Lance Carnes)

These trees are part of San Francisco’s green infrastructure that the city should strive to protect, not heedlessly destroy. And they’re habitat.

THE WESTERN TIGER SWALLOWTAIL BUTTERFLY

Aside from providing nest sites for birds, these trees are the nursery tree of the beautiful butterfly, the Western Tiger Swallowtail. As early as nine years ago, when the Market Street trees were threatened by an ill-conceived street plan, these butterflies were documented as breeding in the London Plane trees (sycamore) that line both sides of market street. (You can read about that here with photos of a just-born butterfly.) These are the famous “Tigers of Market Street” that have been written about in the Smithsonian Magazine, in National Geographic’s Field Notes, in Bay Nature. This little urban ecosystem is a San Francisco treasure – a street that to a bug or bird’s eye, resembles a tree-lined river canyon. Cutting down 50 of these trees is a terrible idea.

(Though the public hearing is over, please do write to SFDPW, your supervisor and to BART about these trees. The relevant Order numbers are: 204929, 204930, 204931, 204932, 204933, 204934, 204935, 204936, 204937, 204938, 204939, 204940, 204941, 204942, 204943)

NOT ENOUGH TREES IN SAN FRANCISCO

Trees are a vital part of urban infrastructure.

• Trees fight pollution, especially particulate pollution that is dangerous to human lungs.
• Trees improve air quality
• Trees are good for physical and psychological health; to get the same benefit as living on a tree-lined street, you would have to be ten years younger.
• Trees provide habitat for wildlife, especially birds and butterflies.
• Trees help regulate water by absorbing it into their roots and gradually releasing it through their leaves.
• Trees reduce crime and improve business.

For a detailed list of benefits, read Twenty Reasons Why Urban Trees are Important to Us All

A group that is trying to save these trees estimates their value at $500,000. In fact, given the infrastructure benefits of trees, that is an underestimate. It’s like putting a value on air: It’s free until you don’t have it, and then it’s infinitely valuable.

San Francisco has too few trees.

Unfortunately, every project seems to start with destroying trees – and neighbors never know about it until it’s a done deal and the trees have 30-days-to-death notices on them. Then they object… but the odds are against them. Though they sometimes succeed in saving the trees, more often it’s too late.  Meanwhile, the City seems to be entirely accepting of tree destruction for any and all reasons.

As of 2013, San Francisco had a tree canopy of only 13.7%, the lowest of any major city, and nearly half the appropriate canopy cover of 25%.  Given that this data is now 8 years old, in an administrative environment that favors cutting down trees over saving them, we expect the current situation is worse.

(From SF Data: In preparation for the San Francisco Urban Forest Plan (2013), the Planning Department performed an Urban Tree Canopy (UTC) Analysis using aerial imagery and additional data sets to determine a canopy estimate for the City & County of San Francisco. This analysis estimated San Francisco’s tree canopy at 13.7%  )

San Francisco Has the Least Canopy Cover of any Major US City

This is an embarrassment for a “green” city, quite aside from the ecological, environmental and health reasons for saving our trees. Unfortunately, between Nativists, developers, and project managers, there seems to be a wave of tree cutting hitting San Francisco. We’re not augmenting our canopy, we’re shrinking it.