Green Wednesday: Nature’s Healing Power and the Future of Street Trees
By Cindy Kerson, U.C. Master Gardeners of Napa County / By Chris Benz, Environmental Contributor
Green Wednesday: Gardening and Ecological Insights
Every Wednesday Napa Valley Features brings you Green Wednesday, featuring articles from environmental voices and the UC Master Gardeners of Napa County. These contributors share research-based horticultural advice, insights on sustainability, ecology and climate topics relevant to our region.
Summary of Today’s Stories
In “How Nature Boosts Brain Function and Well-Being,” Cindy Kerson explains how outdoor activity stimulates brain chemicals such as BDNF and serotonin, supporting cognitive health, mood regulation and immune strength.
“There’s no limit to what being in nature, and especially moving in nature, can do for you.” — Cindy Kerson
In “Why Street Trees Matter in Napa’s Climate Future,” Chris Benz highlights local advocacy efforts to restore tree canopy on Coombs Street and calls for integrated city planning to ensure that urban forests remain part of Napa’s climate and safety strategies.
“Trees are the best traffic-calming measures we can invest in.” — Maureen Trippe
How Nature Boosts Brain Function and Well-Being
By Cindy Kerson, U.C. Master Gardeners of Napa County
NAPA VALLEY, Calif. — A walk in the park, a pause at a window overlooking your garden or a day at the beach. We all know these are rejuvenating moments. But why? What happens in the brain to make them so? What chemical and physiological functions are going on during these experiences?
Until about 200 years ago, humans lived alongside all other creatures — outside. We went indoors for sleep. We foraged, hunted, cooked, worked and played outdoors. Our brains are wired for this connection with nature. Being indoors is evolutionarily meant for protection from dangers such as sabretooth tigers, enemies and weather.
This innate desire for the outdoors is known as biophilia, meaning that we are wired to feel affinity with nature and are attuned to its rhythms. So the next time you feel like disconnecting, think instead that you are connecting — with nature.
Our brains produce a chemical known as brain-derived neurotrophic factor, or BDNF. This signaling molecule, sometimes called neuron fertilizer, serves an important function in the hippocampus, the area of the brain responsible for learning and memory. When we exercise, this chemical is stimulated, which in turn stimulates learning and memory.
Exercising outdoors, as opposed to inside your home or at a gym, provides a double whammy. The areas of our brain that respond to nature are stimulated, which creates a sense of being at peace with our surroundings, while the exercise increases BDNF levels.
Both the human brain and the soil are composted of intricate networks. Our brain relies on many parts to complete a single task. Neurons and many other cells use pathways to send messages to and fro. In the soil, protozoa, fungi, bacteria and other living beings provide a network between plants. They grow and contract to transport nutrients, water and information from plants that don’t need them to those that do.
Some studies suggest that living in a green environment is better for the brain. The Green Heart Project reported improvement in the cognitive skills of young people after they planted thousands of trees in their neighborhoods. Young people in neighborhoods with few trees did not show the same cognitive improvement.
One Finnish study suggests that we may be too clean. If we don’t expose ourselves to nature enough, we don’t benefit from its healing properties. One such natural healer is Mycobacterium vaccae, a soil-derived bacterium known to stimulate production of serotonin. This neurotransmitter, found in the gut and the brain, is responsible for feelings of satiety and well-being. It also contributes to a healthy immune system.
Don’t stop at green, though. Why are we drawn to moving water, such as ocean waves and waterfalls? So we can pick up negative ions, of course. The air around moving water is highly charged with negative ions, considered nature’s air filter. When we inhale them, they positively influence neurotransmitters, boost cell metabolism, improve immune performance and trigger beneficial biochemical processes within the body.
As you consider the hours you need to spend in the garden, don’t worry; you won’t overdo it. The brain also has a natural inhibitor called galanin that will modulate all that BDNF you produced.
There’s no limit to what being in nature, and especially moving in nature, can do for you. And your thoughtful influence on nature, by using integrated pest management practices, is what you can do for it in exchange.
Events
Tree Walk: Take a guided walk through Napa’s historic Fuller Park on Sunday, Oct. 12, from 10 to 11:30 a.m., with a UC Master Gardener docent. Discover some of the many exotic and native trees there and learn some park history. Meet at the corner of Oak and Jefferson streets. The walk is free, but registration is required for each participant.
Fall Clean-Up: Join UC Master Gardeners for the annual fall clean-up at the Las Flores Learning Garden on Saturday, Oct. 25, from 10 a.m. to noon. The garden is at 4300 Linda Vista Ave. in Napa. We’ll be putting gardens to bed for the winter. Learn healthy gardening practices by working alongside Master Gardeners in the low-water, native, pollinator and succulent gardens. Register here.
Help Desk: The Master Gardener Help Desk is available to answer your garden questions on Mondays and Fridays from 10 a.m. until 1 p.m. at the University of California Cooperative Extension Office, 1710 Soscol Ave., Suite 4, Napa. Or send your questions to mastergardeners@countyofnapa.org. Include your name, address, phone number and a brief description of the problem. For best results attach a photo.
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Cindy Kerson is a UC Master Gardener of Napa County.
Why Street Trees Matter in Napa’s Climate Future
By Chris Benz, Environmental Contributor
NAPA VALLEY, Calif. —Street trees do more than beautify neighborhoods; they provide essential infrastructure services. According to a 2020 report from the National Institute of Health, trees directly remove air pollutants, intercept stormwater runoff and provide shade, which can lower local air temperatures and reduce building cooling costs. The loss of mature street trees is particularly significant as they offer greater environmental benefits than smaller trees.
Following the removal of 41 street trees on Coombs Street as part of the city’s Measure T repaving project, Maureen Trippe is on a mission to replace them.
“Street trees save energy, increase property values, reduce stormwater runoff, and make our lives more comfortable and beautiful,” Trippe said.
Trippe views tree replacement as crucial, not only for restoring shade canopy and enhancing climate resilience but also as an investment in traffic calming. As the co-founder of Slow Down Napa, a grassroots organization focused on curbing speeding in residential neighborhoods, she brings her passion for community safety to this initiative.
“The amazing thing is that trees have been shown to reduce vehicle speeds and calm traffic,” Trippe said. “Trees create the appearance that the road is narrower, making drivers feel more relaxed in their presence. Without trees, open spaces give drivers the illusion of control, leading to faster speeds. If a street resembles a highway, people will treat it like one. Trees are the best traffic-calming measures we can invest in.”
The city has plans for street-tree replacement on Coombs Street as part of its ongoing Capital Improvement Project. This includes new trees, a bike lane, traffic safety improvements, street paving and sidewalk repair. However, Trippe noted that the tree replacement plan lacks provisions to fill existing street tree gaps. Additionally, there is no guarantee that every tree removed will be replaced with a new tree since the removal site, typically located in the public right-of-way between the sidewalk and the curb, may not easily accommodate a replacement tree.
Stringent city requirements dictate tree locations and types to prevent roots from interfering with water meters and driveways and to ensure that branches don’t obstruct overhead utility lines. Additionally, a $205 application fee to plant a street tree must be paid by the property owner, who is also responsible for planting and watering the tree. For various reasons — cost, aesthetics or commitment — not every property owner will choose to participate in the city’s street-tree program.
The new Urban Forestry Management Plan will help identify street-tree “opportunity sites” and track all trees removed by developers or city projects. However, the best way to address these sites remains uncertain — the city owns this street-tree space, but the trees require care and commitment from property owners.
A robust tree-replanting strategy for a project of this scale requires more than optional participation from property owners on a case-by-case basis. Trippe emphasized that plans for tree replacement and filling opportunity sites should be integral to the scope of work and budget for future street-rehabilitation projects.
Trippe has taken Bernie Narvaez, her district’s City Council member, on a tour of the Coombs Street trees and has also met with city staff from Public Works to discuss how to fill the street-tree gaps.
“Repaving projects need to consider what truly matters to the neighborhood — they are not just engineering projects,” she said. “I hope the Coombs Street project and its tree-replacement efforts can serve as a model for better preserving and restoring the city’s valuable tree canopy. The carbon sequestered by trees and the shade their canopies provide are clear climate benefits for the community.”
Tree replanting aligns with the city’s climate-action goals and emphasizes the importance of creating a sustainable future. Each tree planted represents a step toward improving the urban landscape and fostering a safer, more vibrant community.
Actions you can take:
Apply for a street tree at the City of Napa Parks and Recreation site.
If you own your home, consider planting additional trees on your property.
Share your view of trees at a City Council meeting.
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Chris Benz is a retired winemaker and co-founder of Napa Climate NOW! Napa Climate NOW! is a local nonprofit citizens’ group advocating for smart climate solutions based on the latest climate science, part of 350 Bay Area. Info, napa.350bayareorg
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