You can make a difference to the hurt being caused by climate chaos and the great extinction event, in your town or your city! How? Reuse, repurpose, and recycle this information.
This is the letter for week 27 of a weekly climate strike that went on for 4 years in front of San Francisco City Hall, beginning early March 2019. For more context, see this story. For an annotated table of contents to see topics for all the strike letters, see this story.
STRIKE FOR THE PLANET
Because parts of SF can be habitable for the next 100 years,
but only if we act now.
We have only 66 weeks left in which to act.1 That’s why this week’s topic is TREES.
SF needs to plant more trees now. Why?
- Trees sequester and store carbon for the long-term.2 Pines, firs, cypress, oaks, and black walnut are among the best at carbon sequestration.3
- Trees reduce the urban heat island effect.4, 5
- Trees save energy.6, 7
- Trees improve urban air quality.8
- Trees create permeable surfaces, reduce runoff, filter and store water, prevent and reduce flooding, and recharge the aquifer.9, 10
- Trees reduce soil erosion.11
- Trees reduce sound pollution.12
- Trees support biodiversity in urban settings.13
- Trees promote environmental justice through improving neighborhood aesthetics, reducing noise, and creating stronger social cohesion and community empowerment in addition to providing cleaner air and access to nature.14
- Big old trees perform all these functions better than young trees. The sooner we put trees in the ground, the sooner they will provide more of these ecosystem services.15, 16 This is why we need to plant now.
SF needs to be planting native trees. Why?
They are the ecological basis upon which life depends, including birds and people. Without them and the insects that co-evolved with them, local birds cannot survive. For example, research by the entomologist Doug Tallamy has shown that native oak trees support over 500 species of caterpillars whereas ginkgos, a commonly planted landscape tree from Asia, host only 5 species of caterpillars. When it takes over 6,000 caterpillars to raise one brood of chickadees, that is a significant difference.17
Trees native to the SF area are:
- California buckeye (Aesculus californica)
- White alder (Alnus rhombirolia)
- Red alder (Alnus rubra)
- Pacific madrone (Arbutus menziesii)
- Water birch (Betula occidentalis)
- California hazel (Corylus cornuta)
- Monterey cypress (Cypressus macrocarpa)
- California buckwheat (Eriogonum fasciculatum)
- California black walnut (Juglans hindsii)
- Juniper (Juniperus californica)
- Tan oak (Lithocarpus densiflora)
- Bishop pine (Pinus muricata)
- Monterey pine (Pinus radiate)
- California poplar (Populus trichocarpa)
- Holly-leaf cherry (Prunus ilicifolia)
- Coast live oak (Quercus agrifolia)
- Canyon live oak (Quercus chrysolepis)
- Red willow (Salix laevigata)
- White willow (Salix lasiolepis)
- Coast redwood (Sequoia sempervirens)
- California bay laurel (Umbellularia californica)
Where should these trees be planted?
Firstly where they are most needed to act as horizontal berms (all the blue spaces on map below). Then in all locations lower than 20 meters elevation. Then in any dense areas not yet planted, as well as around hospitals and schools. Then in replacing all the flammable, non-native trees in forested areas (especially in the Presidio and Parnassus Heights). Then everywhere else, as quickly as possible.
How can SF get trees planted quickly?
We can hold contests or organized events (such as have been done in China, India, Ethiopia, Malawi, etc.), promote the increase in housing value and the decrease in utilities costs that trees produce, work with utilities to make tree planting easy (see this sfpublicworks site18 for an example of how to make tree planting hard – fyi, of the 106 recommended street tree species on this site, only 3 are natives), consider Feng Shui in new tree planting and provide culturally relevant forestry support to prevent destruction of mature trees in newly purchased or inherited properties, legislate trees as part of neighborhood infrastructure, promote the benefits of trees (such as saving lives, for example19), and require specific tree densities per neighborhood.
How can SF maintain its trees?
By utilizing the powers of the purse, the community, and science. Specifically, SF can:
- Give the biosphere legal recognition and rights
- Aggressively pursue grant programs
- Use taxes, fees, and fines to pay for tree upkeep
- Increase the number of required trees per new construction project
- Create neighborhood baseline counts, with increased number goals over time
- Increase the pool of tree ambassadors and give some powers of tree wardens (like in Belfast)
Trees are a public health issue in every way conceivable. Trees are the cheapest and easiest climate crisis activity that must be done right away, due to the time lag involved in growth. We only have 66 weeks left. It’s time to act now!
1. Based on the 2018 IPCC report that world emissions need to peak by 2020 in order to change our path from 3°C (or more) increase to 1.5°C, and that there are only 420 gigatons of CO2 remaining to be used in total.
2. Method for Calculating Carbon Sequestration by Trees in Urban and Suburban Settings. U.S. Dept of Energy. 04-1998. https://www3.epa.gov/climatechange/Downloads/method-calculating-carbon-sequestration-trees-urban-and-suburban-settings.pdf.
3. Greg McPherson’s Tree Carbon Calculator. EarthSky. 07-09-2009. https://earthsky.org/earth/greg-mcphersons-tree-carbon-calculator.
4. New Research on the Impact of Trees on the Urban Heat Island Effect. Deeproot. Nathalie Shanstrom. 18-04-2016. https://www.deeproot.com/blog/blog-entries/new-research-on-the-impact-of-trees-on-the-urban-heat-island-effect.
5. Urban heat islands: cooling things down with trees, green roads and fewer cars. The Guardian. Bianca Nogrady. 20-02-2017. https://www.theguardian.com/sustainable-business/2017/feb/21/urban-heat-islands-cooling-things-down-with-trees-green-roads-and-fewer-cars.
6. How planting trees in cities can save thousands of lives. The Washington Post. Chelsea Harvey. 02-11-2016. https://www.washingtonpost.com/news/energy-environment/wp/2016/11/02/how-planting-trees-in-cities-can-save-thousands-of-lives/.
7. Trees Reduce Building Energy Use in U.S. Cities. U.S. Forest Service. 01-19-2017. https://www.nrs.fs.fed.us/news/release/trees-reduces-building-energy-use.
8. Why We Need Trees in Our Cities. SmartCitiesDive. https://www.smartcitiesdive.com/ex/sustainablecitiescollective/why-we-need-trees-our-cities/1100050/.
9. The Benefits of Trees. Canopy. https://canopy.org/tree-info/benefits-of-trees/.
10. Can we really prevent floods by planting more trees? The Conversation. Roland Ennos. 10-12-2015. https://theconversation.com/can-we-really-prevent-floods-by-planting-more-trees-52160.
11. Good Types of Trees to Stop Erosion. SFGate. Karen Carter. https://homeguides.sfgate.com/good-types-trees-stop-erosion-66797.html.
12. Trees as Sound Barriers. GreenBlue Urban. 23-04-2015. https://www.greenblue.com/na/trees-as-sound-barriers/.
13. Benefits Of Trees. Urban Releaf. 2017. http://www.urbanreleaf.org/get-educated/benefits-of-trees.
14. Environmental Justice and Urban Tree Canopy Cover. National Center for Ecological Analysis and Synthesis. 16-04-2015. https://www.nceas.ucsb.edu/news/environmental-justice-and-urban-tree-canopy-cover.
15. Big old trees grow faster, making them vital carbon absorbers. The Conversation. Adeshola Ore. 17-01-2014. https://theconversation.com/big-old-trees-grow-faster-making-them-vital-carbon-absorbers-22104.
16. Special Issue “Growth and Ecosystem Services of Urban Trees”. Forests. 30-06-2019. https://www.mdpi.com/journal/forests/special_issues/Urban_Trees.
17. Why Native Plants Matter. Audubon Society. https://www.audubon.org/content/why-native-plants-matter.
18. Plant a Street Tree. San Francisco Public Works. https://www.sfpublicworks.org/plant-street-tree.
19. How Urban Trees Can Save Lives. The Nature Conservancy. 31-10-2016. https://www.nature.org/en-us/what-we-do/our-insights/perspectives/how-urban-trees-can-save-lives/.