Yesterday was warmer than expected. Duffy, my dog, ran from shadow to shadow during our afternoon walk. I considered myself lucky to be on a path with some shade, but Duffy might have disagreed, as he ran from side to side, trying to stay cool. It was warm for me, and even warmer for the little guy in a fur coat.
After we returned home, we sat in the shade of a tree. I relaxed, sipping ice tea while Duffy chewed an ice cube. I found myself thinking about trees, drought, and climate change.
There is no question that shade and trees protect us from the direct sun.
I still tend to think of shade as the small patches along a path or in a cool spot in a yard. Or a source of a chuckle: last week along Highway 37, I saw an empty pasture, except for 4 cows sharing a narrow patch of shade from a billboard.
As global temperatures rise, urban areas see larger increases than rural areas outside of cities. This is a function of asphalt streets, which retain and re-radiate more heat from sunlight, than dirt or cement does.
Heat and urban areas don’t mix well. In California in the late 1960’s and early 1970’s, Vietnam war protests turned to bombings and rioting during the warmest months. Many other urban riots have occurred during periods of hotter than average temperatures, across cultures, decades and continents. High temperatures in urban areas are a factor known to increase the probability of social unrest in cities.
Urban social unrest is always a complex phenomenon and violent protests always have multiple sources of discontent.
But today’s combination of economic slowdown, pandemic fears, inflation, and a heat wave that is increasing food insecurity, creates the social kindling that makes riots more likely to occur on hot days. The lack of places to cool off, like parks and shaded areas, adds fuel to this tinderbox.
So while trees can’t solve inequitable systems, shade from trees is an effective way to reduce ambient temperature at the street level, which reduces stress levels for city dwellers. Trees and green spaces improve our moods and make us feel better, a measurable phenomenon known as Biophilia. Urban parks and natural environments provide restful experiences which have been shown to change thought patterns.
As the image above shows, tree-lined streets ARE cooler.
The Warsaw NGO measured the temperature in multiple locations: on the street where asphalt collected heat, on car exteriors, and in the shadows of buildings. The air, or ambient, temperature is impacted by full sunlight in the top photo and the shade from trees in the lower picture.
The chart below translates these temperatures into Fahrenheit:
Amos White, Chief Planting Officer of 100K Trees for Humanity, says, “All told, trees provide 25 ecosystem services, related to air, soil and quality of human lives. Shade is just one of the many benefits to humanity that trees provide.” (A list of these 25 ecosystem services can be found here.)
As we think about the near-term future, the multiple sources of anxiety and how heat puts people on edge, the case for planting more trees grows. Shade is more than a source of comfort while walking. Increasing the number of urban trees is an important component of our individual and community response to climate change.
What can you do?
Remind your city council members, or city managers, that watering parks takes less than 2% of California’s water. Many parks already have irrigation systems that are connected to sources of reclaimed, non-potable water. A surprising number of community administrators are afraid that watering parks, even with non-potable water, will create political blowback for wasting water. Assure them that the public understands using non-potable water for trees and parks is not a waste, and urban trees are a benefit to the community.
If you have a yard, plant a tree. Water it with rinse water from dishes or water (cooled) from cooking pasta. Support organizations that plant trees locally, with money or volunteer hours. Here in the San Francisco Bay Area, sign up to be notified by 100K Trees for Humanity when they call for volunteers.
Trees, once established, are surprisingly resilient and take surprisingly little water once established. Participate in cooling your community by helping grow trees and maintaining shade.