‘L.A. trees are kicking ass': Urban plants capture more CO2 than expected, study finds

Los Angeles Times

19-03-2025

Good morning. Here's what you need to know to start your day.
A new study found they're surprisingly good at absorbing the carbon dioxide we spew into the air with all our cars, energy consumption and corporate industrialization.
Researchers from USC's Dornsife College of Letters, Arts and Sciences published their findings in the journal 'Environmental Science & Technology' last month.
Using an array of sensors set up across a swath of central L.A., the team tracked CO2 emissions during an 18-month period. Over the course of a year, trees absorbed up to 60% of CO2 emissions on average during daytime, according to the study — significantly more than expected.
'That's a huge number,' said Will Berelson, an earth sciences professor at USC who led the study. His initial reaction to the data wasn't quite scientific enough to include in the journal, but I think it works just fine for this newsletter:
'Wow … L.A. trees are kicking ass.'
All aboard the CO2 Express
Berelson's team approached the measurements similar to how a transit agency would measure ridership. That was possible, he explained, because of L.A.'s predominant wind, which moves from west to east, taking CO2 along for the ride.
Using a dozen sensors, researchers tracked this CO2 Express across a roughly 30-square-mile section of the city, from about La Brea Avenue between 3rd Street and Obama / Exposition Boulevard and northeast into Boyle Heights and Lincoln Heights neighborhoods.
'We're actually watching as the air is moving across the city,' Berelson told me. 'We're seeing the change happening before our very eyes with these sensors — what's happening on the west side and then towards the middle of the city and then farther to the east side — we can actually see changes as the air is passing.'
The data showed decreases in CO2 that indicated trees in the area were capturing up to 60% of emissions on average during daytime (trees and vegetation only absorb CO2 during photosynthesis, which requires sunlight). That works out to about 30% on average in a full 24-hour day, Berelson noted.
What actions could the research help inform?
Berelson is hopeful the model could be used by other cities looking to track and reduce CO2 emissions.
He was also surprised how much CO2 trees in the area were able to capture, considering 'this is a part of L.A. that doesn't really strike you as being all that green.'
That lack of trees has been an ongoing challenge in the city, with studies finding stark disparities in which communities experience the benefits trees provide through shade, heat mitigation and cleaning the air.
Berelson said expanding on this study could help L.A. and other cities 'be quantitative [and] scientific about how we plan tree planting.'
And while urban trees have demonstrated 'uncanny ability to take up a lot of CO2 quickly,' he emphasized that just planting a lot more trees isn't a solution to the region's air quality and climate crises.
'Emission reduction has to happen,' Berelson said.
More tree studies are in the works
A greenhouse study is underway at USC to see which species of trees capture the most carbon, which Berelson said has been 'fascinating' so far.
'We actually have to take a careful look at what types of trees we're planting, because it can make a big difference … in terms of how much CO2 we can take up,' he said.
That study will also analyze how trees are affected by a warming climate, which Berelson said will affect CO2 uptake.
And while this initial study area included major freeway intersections (including the 10, 110 and 5) it did not take a granular look at emissions near those emission-heavy roadways. Berelson's team will work to parse the data moving forward, he told me.
The researchers also recently installed more sensors on each end of the initial study area, giving them 'a longer train to look at,' Berelson said.
Those follow-up studies are likely a year or more away, so stay tuned!
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His impressive basement saloon was like 'Cheers' — until it burned in the Eaton fire. Before the January fires came, Brian Gardner had 300 Polaroids on the wall of his basement saloon, the Hye West Saloon of Santa Poco. He had over 1,000 bottles of booze too. But the Polaroids he hung around the perimeter of the 300-square-foot bar nestled in a storage room under some stairs at his Altadena home were more important to him.
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Victoria Loch writes: ''The Long Goodbye' by Raymond Chandler. As a born and bred NYer and long time Californian, this is the essence of the state (and state of mind) to me. Less convoluted than 'The Big Sleep,' this captures all the glory and sadness and insanity that is California.'
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Today's great photo is from Times photographer Genaro Molina at the site of Diane and Verne's Altadena home where they lived for 50 years. It was destroyed in the Eaton fire, and they are determined to rebuild it as a legacy gift to their family.
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