Los Angeles is notorious for its traffic congestion and air pollution, but a surprising discovery has revealed a natural ally in the fight against carbon emissions—its trees.
A groundbreaking study has found that L.A.’s urban canopy absorbs up to 60% of daytime CO2 emissions during summer, reshaping how we think about city-based climate solutions.
This research, published in Environmental Science & Technology, is a wake-up call for urban planners.
While green spaces are often valued for their aesthetics and recreational benefits, this study suggests that trees are doing far more than providing shade—they’re acting as silent carbon scrubbers, significantly reducing fossil fuel emissions in ways previously underestimated.
A New Way to Measure Carbon in the City
For years, scientists have relied on indirect methods like economic models and energy use data to estimate urban carbon emissions.
However, researchers at USC Dornsife College took a different approach—they installed a network of high-resolution BEACO₂N sensors across a 15-by-6-mile section of central Los Angeles.
These sensors provided real-time data on CO2 levels, tracking emissions as they moved through the city’s dense freeway system.
Instead of relying on assumptions, scientists were able to measure the actual impact of urban greenery on air quality.
“You can think of emissions like passengers on a train,” explained Dr. Will Berelson, lead researcher of the study.
“As the wind moves pollution through the city, some gets picked up and some gets dropped off. These sensors let us see that process in real time.”
By comparing carbon monoxide (CO) levels—often a reliable indicator of fossil fuel emissions—scientists were able to differentiate between pollution from cars and industry versus natural sources like decaying plant matter.
Trees Absorb More CO2 Than Expected
What they found was startling.
During peak growing months, L.A.’s trees absorbed up to 60% of fossil fuel-generated CO2 emissions during the day—a far greater percentage than previously assumed.
On an annual basis, trees offset about 30% of the city’s fossil fuel emissions.
This puts Los Angeles among the world’s top cities in urban carbon absorption, proving that even in dry climates, trees can play a major role in mitigating pollution.
But how can trees be absorbing so much CO2, especially in a city with minimal rainfall? Researchers suspect three key factors are at play:
- Irrigation Systems: Many trees are kept alive through underground irrigation, often from leaky pipes.
- Resilient Tree Species: Certain species thrive in urban conditions and continue absorbing CO2 even during dry months.
- Groundwater Access: Trees with deeper roots may be tapping into hidden underground water sources.
The Pattern Interrupt: Trees Alone Won’t Solve the Problem
Despite their incredible impact, trees alone cannot compensate for the sheer volume of emissions generated by traffic and industry.
The study found that CO2 levels still spiked during rush hours, demonstrating that fossil fuel use remains the dominant factor in urban air pollution.
“Nature is helping us,” Dr. Berelson emphasized, “but we can’t rely on it to do all the work.”
The takeaway? Planting more trees is important, but cutting emissions is critical. This means investing in:
- Clean energy alternatives
- Expanded public transportation
- Stricter vehicle emissions regulations
Expanding the Research: Mapping Carbon Across L.A.
Encouraged by these findings, scientists are expanding their monitoring efforts, adding eight more BEACO₂N sensors across Los Angeles.
These new sensors will provide a more detailed map of carbon absorption, identifying:
- Where trees are most effective at reducing pollution
- Which neighborhoods need more greenery
- How CO2 levels fluctuate throughout the city
By integrating atmospheric modeling with real-world data, researchers can now track emissions more accurately than ever before.
This method was previously used to measure COVID-19 lockdown emissions, revealing a 50% drop in traffic-related CO2 during that period.
Now, scientists hope to apply the same tracking to long-term climate planning.
A Blueprint for a Greener Future
Los Angeles has set a bold goal to become carbon-neutral by 2050, but reaching that target will require a combination of policy changes, technology, and urban reforestation.
The USC Urban Trees Initiative is one step in that direction.
In partnership with the city, researchers are using BEACO₂N sensor data to guide tree-planting projects, prioritizing low-income neighborhoods that suffer from the highest pollution levels.
This study proves that strategically planted urban greenery can make a tangible difference, absorbing massive amounts of carbon that would otherwise linger in the atmosphere.
But it also serves as a reminder: while nature provides powerful solutions, the ultimate responsibility falls on humans to reduce emissions at the source.
With cutting-edge carbon tracking and smart urban planning, Los Angeles could become a model city for balancing nature and technology—proving that even in the most unexpected places, solutions to climate change are taking root.
