May 2013: Mount Sutro Forest Hike in a Dry Spell

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.

still lushThe forest is beautiful right now. Even the small plants and grasses by the trail edge aren’t dying or stressed by drought.

Sutro Forest - herbaceous layer is still green

Mount sutro forest - still green

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.

Mount Sutro Forest with visitors

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…


There are a few dry areas. The grass  in the Native Garden is beginning to yellow.

yellowing grass in Mount Sutro's  Native Plant GardenBut the worst spots are areas where the understory has been removed and left covered in sticks and bark.

Undergrowth removal dries out the forest

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.

understory removed along East Ridge trail

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6 Responses to May 2013: Mount Sutro Forest Hike in a Dry Spell

  1. Tony Holiday says:

    Excellent, sensible comments. UCSF and Stewards, please read! What you say is plain common sense and hopefully they will see reason.

  2. All I can say is save the Sutro Forest. Leave it alone and let nature run her course.

  3. Ryan Robertson says:

    I think it’s unfortunate that you’re misleading the public by stating that UCSF should discourage the Sutro Stewards from removing the understory. I’ve followed this Sutro issue for some time now and attended many of the public meetings and I’ve read much of what you have stated on your website about the Stewards. It’s disappointing that you seem to hold them responsible for much of the plans that UCSF has for Sutro. UCSF owns and controls this Reserve, not the Stewards. UCSF makes the decisions about how the land is managed, not the Stewards. Yet, in your writings you make the issues appear that the Stewards control what UCSF does with the Reserve.
    The Stewards cannot simply go up and remove understory at their own discretion.

    [Webmaster: Hi Ryan, thanks for stopping by to comment. We admire a lot of what the Sutro Stewards do. They keep the trails open, and they manage the Native Garden without using *any* pesticides – unlike the city’s own ‘Natural Areas Program,’ which has been using increasing amounts of pesticide.

    But they do most of the work in the Reserve and run the Native Plant Nursery in the Aldea area. Their Executive Director, Craig Dawson, is a long-standing member of UCSF’s Community Action Advisory Group [and Parnassus Community Action Team]. We do think – and this is an opinion – that this gives them a great deal of say in what is done in the Reserve. Unless there are opposing instructions from UCSF, we would expect the Sutro Stewards to lead the direction of work in the Reserve. Mr Dawson supports felling large numbers of trees, and using pesticides.]

    I hope you allow my comments to be posted on your website.. This is neither a flame, nor an argument, but a statement of opinion.

    [We do try to post all comments. But we don’t do flames or ad hominem attacks or personal remarks. We’re fine with arguments, and have only cut them off maybe twice in four years when they became repetitive and pointless.]

    I value your effort in maintaining Sutro as a haven for nature, but I am sorely disappointed in the way in which you point the finger at a volunteer group that has made it possible for YOU and those who support your effort to actually enjoy the Reserve.

    [Thanks. We hope this clarifies that we’re not opposed the the Sutro Stewards per se, but are disappointed in some of their activities – like mowing down or tearing out understory – and in their apparent stance about trees and pesticides. We do appreciate their keeping the trails open – but would like to mention that people have been enjoying the forest for decades before the Sutro Stewards started work there.]

  4. harry says:

    why oh why do they keep thinning the forest? you’re right, it’s noticeably drier in some spots. it used to be muddy year round, but now with the canopy thinned so much, this is the first year we see so many dry trails. please, please stop doing this, and let the canopy grow back!

  5. milliontrees says:

    Ryan might find it helpful to understand the relationship between the Sutro Stewards and UCSF to read the Stewards’ public comment on the Draft Environmental Impact Report (DEIR) for the project. UCSF has made all the public comments available to the public here:

    The Executive Director of the Stewards says in his letter that although he supports the project, he is not satisfied with several aspects of the project. He wants more trees destroyed than proposed by the DEIR so that there is more space and sunlight for the native plants and trees that he would like planted. Consistent with that criticism he doesn’t think the DEIR commits to planting as many native plants and trees as he would like. And he would like more herbicides to be used to control non-native trees and vegetation.

    So, Ryan is actually right that the desires of UCSF for the future of Mount Sutro don’t match exactly with the Sutro Stewards. However, based on this public comment, it seems that they want an even more extreme make-over of the forest.

    Another reason why Ryan and others might find the public comments interesting is that they would learn that critics of the plans and those who are opposed to them overwhelmingly outnumber the few comments that support the plans. Many of the comments come from neighbors of Mount Sutro who believe that the destruction of most of the forest will have a negative impact on their microclimate such as wind and noise. And many of the comments are from people who know the forest and love it just as it is.

  6. gina hall says:

    Leave the forest alone. Everywhere that has been thinned so far is so NOT beautiful, It is an eyesore. To return San Francisco to ‘native’ is to return it to sand dunes. Will the cliffs on the Great Highway be the next to go? Where does one stop with this distruction?

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