Why not plant oak trees to help ease pollution?

by Mark von Wodtke | Special to the Courier

Although smog has diminished, the inland valley does not always meet federal health limits. The Mira Loma station monitoring nitrogen oxides levels routinely records high concentrations of smog and lung-damaging soot due to fine-particulate pollution.

Higher levels of air pollution create greater risk of asthma, heart disease, lung deficiencies and a variety of other ailments. The smog situation must improve as freeways are now being made even wider, inviting more traffic through Claremont and the Inland Empire.

We can reduce smog producing emissions from tailpipes. We also need to intercept particulate emissions from tires and brakes. These contribute to fine particulate matter of 2.5 microns or less in diameter (PM2.5), which induce adverse health effects, and those with a diameter of 10 microns or less (PM10), which are inhalable into the lungs. In addition, we need to reduce emissions of air pollution and water contaminants. There is a lot we can do to protect people’s health and reduce climate change.

In Colleen Fisher’s 2017 master’s thesis at the Lyle Center for Regenerative Studies at Cal Poly Pomona, “Interception of Particulate Matter by Street Tree Leaves,” she selected trees from Claremont and found the native Quercus agrifolia (live oak) is the best to plant along streets in the inland valley. Live oaks improve air quality, and its small, waxy, evergreen leaves are the best at capturing PM10 and PM2.5 particles in the inland valley.

The soil seems to be a good place to store particulates that run off tree leaves without affecting people’s health. But we also need to monitor water quality, which affects ground water, to make sure air emissions do not cause damage to our ground water.

What can we do to clean up air and water pollution? Claremont could innovate with a clean air canopy of 100 oaks along the 210 Freeway at the Baseline Road right of way.

The prevailing winds from Los Angeles and the LA harbor carry with them high pollution emissions, affecting our inland valley. When the wind is blowing in from the west this polluted air travels along the 210 Freeway, past the Whole Foods Market Shopping Center and the denser areas between Claremont and Upland. Implementing stricter emissions regulations for the shipping industry would help alleviate this problem.

Cooler fresh mountain air flows naturally from Mt. Baldy and moves in a downward vortex through San Antonio Canyon into Claremont and Montclair. This air moves past the 210 Freeway onramp at Baseline Avenue where it is polluted from freeway emissions and flows into Claremont. Along this path is the Claremont Club, where many people exercise. Air flowing in this direction also arrives at the Claremont Colleges, where poor air quality can affect cognition. Studies have shown schoolchildren in badly ventilated classrooms who ride in gas-powered school buses have diminished IQ’s when compared to children with better ventilation.
In 25 years, we should have many more electric cars, but particulate matter from tires will still result in PM10 and PM2.5 emissions. Trucks will also move increasingly to electric power, avoiding diesel exhaust. Reducing emissions reduces breathing difficulties, especially where heavy vehicles need to accelerate. Planting oak trees in these micro ecosystems can help intercept these emissions. The Claremont Colleges already have oak groves extending into the Village along Sixth Street. These oaks need to be sustained and regenerated. This can also help us deal with watershed pollution. Why not plant oaks where we can?

Mark von Wodtke, FASLA, is a Fellow of the American Society of Landscape Architecture and Professor Emeritus of Landscape Architecture at Cal Poly Pomona.


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