We’ve had an unusually dry winter here in California, and even San Francisco’s had a hot spell recently. So what’s happening in Mount Sutro Forest, usually so damp and green?
In brief: It’s not damp, but it is green. The trails are all dry now – and the understory is still green and lush where it’s been allowed to thrive.
This fine Sunday afternoon, we encountered a few other people – maybe a dozen hikers, two with dogs and one with a baby; two joggers, one with music; and a bicycle rider.
There’s been quite a lot of understory removal in various areas; while this destroys habitat, it does make the birds easier to spot. (We’re unsure this is an improvement from the bird’s point of view.) There were wrens darting around under the blackberry bushes, juncos flying around the forest, bushtits busily foraging…
CREATING A FLAMMABLE FOREST
There are a few dry areas. The grass in the Native Garden is beginning to yellow.
As a result of talking up of the fire hazard – irresponsibly, in our opinion – people have become concerned. Here’s reader Thom Taylor’s comment on our previous post: ‘…you keep mentioning that Sutro is a “cloud forest”, but with the record heat we’ve experienced over the past week and a half we haven’t seen a drop of moisture in the Bay Area. I was hiking Sutro yesterday and it is incredibly dry up there right now. Are you arguing that even during these spurts when we experience extremely warm temperatures that a dry forest like Sutro would pose no fire danger?’
As these photographs show, the fire danger is not from the forest where it’s lush and dense. The plants there remain green year round – even through dry spells like this one – so they contain and retain moisture. They slow evaporation by trapping moisture, protecting it from sun and wind. Moisture content is an extremely important factor in reducing fire risk.
But this forest, that usually has a very low fire risk, can be made more flammable. When the understory is mowed down or ripped out, and instead there’s flammable sticks and bark. Or when it’s opened enough that the small plants and grasses actually do dry out – like in the Native Garden.
There’s been no rain for over 2 weeks. But the forest still hasn’t dried out, unlike the Native Garden grasses. The trails are dry, but the plants are not.
We’ve had no rain these past two weeks, but we have had a little fog some nights – and that’s been enough to keep the forest green. The trees harvest the moisture, and the layers of vegetation conserve it by retarding evaporation. This is the mechanism that the Plan will destroy.
With 90% of the trees and understory gone, the moisture will quickly evaporate. The increased wind will worsen the effect. The driest parts of the forest right now are where the Sutro Stewards have denuded the trails of their understory.
If UCSF was actually concerned about fire hazard, here’s what they would do:
1) Discourage the Sutro Stewards from removing this dense green understory. Blackberry and ivy don’t burn readily. Cape Ivy is particularly fire-resistant because of its high moisture content.
2) Check to ensure that the Native Garden’s existing irrigation system remains functional, even if the plants are not irrigated once they are established. The Native Garden has fine fuels in the form of dry grass, and is probably the most flammable area of the forest.
3) Encourage forest neighbors to check for fuel build-up on their roofs, especially in winter when they may be using their fireplaces. This could be done by simply sending round flyers once or twice each season.