Pesticides on Mt Davidson

Observers have pointed out that Mt Davidson is one of the worst places in the city to spray with toxic herbicides. But despite that,  the Natural Resources Department (NRD – formerly Natural Areas Program, NAP) sprayed toxic herbicides 15 times in 2017. Many of these sprayings happened in November and December, when they’re targeting oxalis with Garlon. And they’re still doing it. This video was taken in March 2018, as were most of the pesticide pictures in this article.

4 people in protectiv suits spraying herbicides on Mt Davidson, San Francisco, in March 2018


Mt Davidson is a steep hill, surrounded by residential areas where families live – some of them with small children and many with pets. It’s just above an elementary school.

It’s part of the watershed for Glen Canyon, and the run-off feeds into the creek there – which runs just below a playschool for little kids. Because it’s in the fog belt and harvests moisture from the fog, it’s wet year-round – in winter from the rain, and in summer from cloud-forest precipitation.

This increases the likelihood that the chemicals are going to be carried down. Both Mt Davidson and Glen Canyon are popular with families, including pets. (Glen Canyon was even worse off – it got sprayed 30 times in 2017.)

One would think that this is an area that San Francisco’s Recreation and Parks Department (SFRPD) would declare a pesticide-free zone. It’s not happening. We’re just starting to collect the 2018 data, but we already have evidence that there’s been no let-up. The Mt Davidson pesticide notice pictures here are from March 2018.


Mt Davidson continues to be a target for the most hazardous Tier I and Tier II herbicides San Francisco’s Department of the Environment (SF Environment). SF Environment ranks pesticides into three tiers: Tier III is least hazardous, Tier II is More Hazardous; and Tier I is Most Hazardous.  On Mt Davidson, as in other “Natural Resource Areas” they use the “Fearsome Four”herbicides: Roundup/ Aquamaster (glyphosate); Garlon (triclopyr); Stalker/ Polaris/ Habitat (imazapyr); and Milestone VM (aminopyralid).

  • Roundup or glyphosate – the chemical the World Health Organization considers a probable carcinogen, and which is potentially an endocrine disruptor. It’s been rated Tier I in recent years; before that, it was Tier II.
  • Garlon or triclopyr – a chemical that has been Tier I since 2009 at least, and always carried the notation “HIGH PRIORITY TO FIND AN ALTERNATIVE.
  • Polaris/ Stalker/ Habitat or imazapyr – a chemical that is mobile in the soil, and can affect not just the vegetation sprayed but plants and trees nearby. It’s also very persistent and doesn’t biodegrade easily.
  • Milestone VM or aminopyralid – a chemical that is even more persistent, so persistent that if animals eat it, their poop is still toxic. The UK prohibited its use for some years, and New York forbids its use because they’re afraid it will get into the watershed.


The Natural Resources Department (NRD) is the land manager here, and it’s their call on what to use, when, and how much. SF Environment can decide what herbicides are allowed on the list, but they do not influence amounts, locations, or frequency. That’s on the NRD.

The herbicides are applied by the Natural Areas program staff, who are city employees.

In addition, the city contracts with Shelterbelt, which also comes out and sprays herbicides. Sometimes they operate independently, while at other times, a mixed team of Shelterbelt and NRD staff go out together. The day these photographs were taken, Shelterbelt was also there.


San Francisco has another mountain forest surrounded by residential neighborhoods – Mt Sutro Cloud Forest.

A part of that is owned by the city, but the larger part of it is owned by University of California San Francisco. Though we disagree with much of the plan UCSF has for Mt Sutro, primarily because of the planned destruction of thousands of trees – there is one thing they are getting right. They have banned pesticide use in their part of Sutro Forest.

In 2013, UCSF issued a statement that included these words:

“…as a health sciences university, we believe the right thing to do is not to use herbicides in the Reserve.”

In fact, they have used no pesticides in the forest since 2008, and in the Aldea Student Housing since 2009. With this statement, they confirmed they would not be using them at all.

We think this is an example that SFRPD – and especially NRD – could follow.






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