LA’s Trees Absorb More Carbon Than Expected, But Can’t Do It Alone

A groundbreaking study from USC Dornsife College has found that trees in central Los Angeles absorb significantly more carbon dioxide than previously estimated, offsetting up to 60 percent of daytime fossil fuel emissions in the warmer months and about 30 percent annually. Using an innovative network of high-resolution CO₂ sensors called the Carbon Census array, researchers tracked emissions in real time, providing one of the most detailed measurements of how urban greenery impacts air quality. Unlike traditional models that estimate CO₂ levels indirectly, this study measured carbon emissions directly over an 18-month period, yielding a more precise understanding of how vegetation interacts with urban pollution.

One of the most surprising findings was that trees absorbed the most carbon dioxide during summer, despite the season’s dryness. Researchers attribute this resilience to irrigation, groundwater access from leaky infrastructure, and drought-resistant tree species. However, while urban trees play a critical role in improving air quality, they cannot fully offset emissions from cars, buildings, and industry. CO₂ levels still spiked during rush hours, reinforcing the need for broader systemic changes. The study supports the USC Urban Trees Initiative, which seeks to expand greenery in communities most in need, using data-driven insights to guide tree planting efforts where carbon absorption is highest.

Looking ahead, researchers are expanding the sensor network to cover more areas of Los Angeles, helping to define baseline CO₂ levels and identify regions where vegetation can make the biggest impact. While urban trees provide a natural boost to carbon reduction, lead researcher Will Berelson emphasizes that they are not a substitute for larger climate solutions. “Nature is helping us, but we can't rely on it to do all the work," he said, underscoring the need for clean energy, better public transit, and broader emissions reductions to meet the city’s goal of carbon neutrality by 2050.