San Francisco Department of the Environment

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Annual Urban Forest Reports

Overview of San Francisco’s Urban Forest, FY 2016-2017

SF Environment staff surveyed 21 City departments, public agencies, and non-government organizations that oversee or manage a portion of the urban forest in San Francisco. Organizations were asked to provide information on forestry budget and staffing, maintenance activities, accomplishments, and concerns in fiscal year 2015-2016. Of the 21 organizations surveyed, 19 provided full or partial responses.

This data is tracked to:

  • Better understand the resources used to maintain the urban forest across the city.
  • Track the priorities, needs, and concerns of city departments and local nonprofits, and monitor how they change over time.
  • Better understand threats to the future well-being of our urban forest.
  • Find ways to increase the contributions that trees provide to our community.

Primary Findings:

The data provided by participating agencies for this report is compared to data provided since FY14-15. While participation is required by Chapter 12, Section 1209 of the San Francisco Environmental Code, not all agencies participate in the survey each year. 

Figure 1. Trees & Funding: Reported tree planting and urban forestry budgets since FY14-15 (12 agencies)

three year trends - all tree activities and budget

 

In the last three years, the reported annual number of trees planted in San Francisco peaked in FY14-15 with 2,877 trees. Overall tree planting and maintenance numbers have steadily decreased each subsequent year, culminating in the fewest number of trees planted this year at 2,073, a 15 percent decrease in the average total annual trees planted during this three-year period. FY16-17 tree maintenance activities have decreased by 25 percent of the annual average during this period. Much of this decrease can be attributed to Public Works’ program to relinquish the maintenance responsibilities of street trees to adjacent property owners (Proposition E ended this program and reverted street tree responsibility back to Public Works). Tree removals have increased, peaking in FY15-16 at 2,069 trees removed and remaining close with 2,000 trees removed this past year. Reported tree removals rose 6 percent in FY16-17 from the three-year annual average, and a 27 percent increase from removals in FY14-15.

The total urban forestry budgets reported by each responding agency since FY14-15 does not follow the trends in tree planting, maintenance, and removal activities. Overall urban forest funding increased significantly in FY15-16 because Public Works reported a significant increase in funding to implement the relinquishment program. Urban forestry budgets dropped again in FY16-17, but are still 14 percent higher than the annual average for the three-year period. Budget trends will change significantly next year with the addition of funding to Public Works under Proposition E. It will likely take a few years before tree planting, maintenance, and removal numbers reflect this large increase in funding.

Figure 2: Tree Planting & Removal Trends Since FY14-15

three year trends - planting and removals

The reported tree planting and tree removal numbers since FY14-15 demonstrate a closing gap. Based on reported data, only 111 more trees were planted in FY16-17 than removed in San Francisco. This is a significant finding of concern that predicts a decrease in canopy and overall benefits provided by San Francisco’s urban forest.

Trees removed may be any variety of size, maturity, and health. Therefore, the amount of benefits lost by the removal of such trees is likely greater than those provided by newly planted trees, which are significantly smaller and provide fewer benefits than the potentially large and healthy trees that were removed. Additional data about the specific trees removed and trees planted is needed to identify actual loses and gains in urban forest benefits. Such data is not currently requested of participating agencies in the annual survey.

Based on the concerns of many reporting agencies, the effects of the drought, pests, and disease may be largely contributing to the increase in tree removals. Governor Jerry Brown declared the drought emergency over for most of California in April 2017, but trees take time to recover from the cumulative effects of a long-term drought and the significant rainfall of the 2016-2017 winter may not be enough for many trees to recover from the damage caused by the previous dry winters - especially large and mature trees. Agencies such as SFO, Zuckerberg General Hospital, and SFSU reported concerns with declining health of redwood trees (Sequoia sempervirens) under their care. This iconic California native tree is not drought tolerant and current research shows that specimens planted in landscape settings outside of their native areas are suffering from water restrictions and irrigation with non-potable water throughout the Bay Area. Redwood trees’ water and other cultural needs should be considered when planning future plantings since periods of extreme drought are expected to continue as the climate continues to change.

The stress of the drought makes trees more susceptible to pests and diseases. Several agencies reported concerns with pines (Pinus spp.) and myoporum (Myoporum laetum), two widely-occurring tree species in San Francisco that are declining in health. Drought-stressed pines are more likely to be attacked by bark beetles (Ips spp.) and less likely to survive. Additionally, many declining pines, primarily Monterey pine (Pinus radiata), are infected with pine pitch canker (Fusarium circinatum), a fungus that obstructs water flow and causes the loss of branches and potentially the death of the tree.

Myoporum is one of the few tree species that thrives in coastal conditions on the western side of San Francisco. Unfortunately, myoporum trees are being ravaged by the species-specific myoporum thrips (Klambothrips myopori) from the tree’s homeland of New Zealand that eventually kills the tree in our environment due to the lack of natural predators. Rec & Park planted thrips-resistant Myoporum cultivars this year and Public Works is also interested in how effective these cultivars are at minimizing thrips damage.

Read the full 2017 Annual Urban Forest Report here >


Past Annual Urban Forest Reports

2016 Annual Urban Forest Report
2015 Annual Urban Forest Report
2014 Annual Urban Forest Report
2013 Annual Urban Forest Report
2012 Annual Urban Forest Report
2011 Annual Urban Forest Report
2010 Annual Urban Forest Report
2009 Annual Urban Forest Report
2008 Annual Urban Forest Report

 

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