Improved air quality could enhance natural carbon sequestration by plants

(Adapted from a press release by the Carnegie Institution for Science.)

Reducing pollution from aerosol particles would improve air quality. It could also increase the amount of sunlight accessible to plants—enhancing their ability to remove carbon dioxide from the atmosphere and mitigate climate change. A new study coauthored by David Lobell, director of the Stanford Center on Food Security and the Environment, used satellites to measure both photosynthetic activity and aerosol pollution in Europe. The findings demonstrate that plants capture more carbon on the weekends when industrial production is decreased, and fewer people commute.

“The notion that pollution is bad is obviously not new,” Lobell said. “But now we can begin to understand just how much it matters for a variety of things, which is useful information for policy decisions.”

Their paper, published in Proceedings of the National Academy of Sciences, was led by scientists at the Carnegie Institution for Science.

Plants have a special ability, called photosynthesis, by which they convert the sun’s energy into chemical energy. To accomplish this, they take in carbon dioxide from the air and fix it into carbohydrates and fats.

This everyday process is a huge help in the fight against climate change caused by human activity. Plants pull some of our carbon pollution out of the atmosphere and retain it as a biological matter, preventing it from contributing to global warming.

Previous work has shown that aerosol pollution can suppress agricultural crop yields by as much as 20 percent.

Because one step of the photosynthetic process releases fluorescence, it can be seen from space and measured by satellites—a game-changing research method. The research team used satellite measurements of photosynthetic activity in Europe. They correlated their photosynthesis findings with aerosol measurements and used modeling to understand the relationship.

The work showed a weekly cycle of photosynthetic activity, which peaked on the weekend and diminished during the week, the exact inverse of the patterns of aerosol pollution. They also found a similar pattern during COVID-19 lockdowns when people were sheltering at home instead of commuting.

If particulate pollution could be curtailed throughout the week, maintaining weekend levels of photosynthetic activity all the time, it would remove between 40 and 60 megatons of carbon dioxide from the atmosphere and trapping it in biological matter. It would also increase agricultural productivity without increasing the amount of land used for growing crops.

“This type of study is only possible because satellites can now measure both photosynthesis and air pollution at daily frequencies,” Lobell said. “This allows us to learn from changes that occur on weekends, when some pollutants are slightly lower.”