Reducing air pollution could greatly boost carbon sequestration by plants

Better air quality can significantly enhance natural carbon sequestration by plants, according to a new study from the Carnegie Institution for Science.

Improved air quality increases sunlight availability for plants, thereby boosting their ability to absorb atmospheric carbon dioxide and mitigate climate change.

Critical insights 

The team, including researchers Liyin He, Lorenzo Rosa, and Joe Berry, used satellite data to analyze the correlation between photosynthetic activity and aerosol pollution in Europe. 

The results showed that plants capture more carbon on the weekends when there is less industrial pollution and fewer people commute. 

This finding highlights the impact of human activities and air quality on the natural carbon absorption process of plants.

Aerosol pollution 

Photosynthesis, a vital process where plants convert sunlight into chemical energy, involves absorbing carbon dioxide and converting it into carbohydrates and fats. This natural mechanism plays a crucial role in combating climate change by removing carbon emissions from the atmosphere. 

“However, this can be diminished by poor air quality caused by aerosols, tiny particles that are spewed into the atmosphere when we commute and burn fossil fuels or wood,” explained He. “They have negative effects on air quality, which impacts human health. They can also scatter or absorb sunlight, which would affect a plant similarly to being stuck in the shade.”

Previous studies have indicated that aerosol pollution can reduce agricultural crop yields by up to 20 percent.

Innovative technique 

The research involved collaboration with David Lobell and Yuan Wang from Stanford University; Yi Yin, Yitong Yao, and Christian Frankenberg from Caltech; and Russell Doughty from the University of Oklahoma. 

The team used the TROPOspheric Monitoring Instrument (TROPOMI) on the Copernicus Sentinel-5 Precursor satellite to measure photosynthetic activity. 

This innovative technique, developed about a decade ago by Berry, Frankenberg, and Caltech collaborators, leverages the fluorescence emitted during photosynthesis, observable from space.

Photosynthetic activity 

The team compared photosynthesis data with aerosol measurements from the Visible Infrared Imaging Radiometer Suite. 

“We focused on Europe due to an established pattern of human activity throughout the week as compared to other regions,” Rosa said. “Additionally, many European ecosystems are already experiencing negative effects from climate change and European countries have set ambitious goals for cutting carbon pollution.”

The findings revealed a weekly cycle in photosynthetic activity, peaking on weekends and decreasing during weekdays, inversely correlating with aerosol pollution levels. 

Study implications 

A similar pattern emerged during COVID-19 lockdowns. The research suggests that reducing particulate pollution to maintain weekend-level photosynthetic activity throughout the week could remove 40 to 60 megatons of carbon dioxide annually, increasing agricultural productivity without expanding crop land.

“These findings have major policy implications for European governments who are working on a variety of systems to capture about 500 megatons per year of carbon dioxide out of the atmosphere and store it,” said Rosa. “Our work shows that improving air quality could also help meet climate goals.”

More about carbon sequestration 

Carbon sequestration is a critical process in the fight against climate change. It involves the capture and storage of atmospheric carbon dioxide (CO2), one of the primary greenhouse gases responsible for global warming. This process can occur both naturally and through human-engineered methods.

Plants

In natural carbon sequestration, ecosystems like forests, oceans, and soil play a pivotal role. Trees and plants, through the process of photosynthesis, absorb CO2 from the atmosphere and convert it into organic matter. 

This CO2 is stored in the form of biomass in trees, plants, and soil. Healthy, growing forests, therefore, are essential carbon sinks, storing large amounts of carbon over long periods.

Oceans

Oceans also sequester a significant amount of carbon, absorbing it from the atmosphere and storing it in various forms. Phytoplankton, small marine plants, use CO2 for photosynthesis, similar to terrestrial plants. The carbon can then become part of the oceanic food web or settle as sediment on the ocean floor.

Soils

Soils are another crucial component in natural carbon sequestration. They store carbon in organic matter, such as decomposed plant and animal material. Practices that enhance soil health, like organic farming and reforestation, can increase the amount of carbon that soils can sequester.

Technologies

Human-engineered carbon sequestration methods aim to complement these natural processes. These include technologies like carbon capture and storage (CCS), where CO2 emissions from industrial and energy-related sources are captured at their point of origin and stored underground in geological formations.

Bioenergy

Another method is bioenergy with carbon capture and storage (BECCS), which combines biomass energy generation with CCS. In this process, biomass is used as a fuel to generate energy, and the resulting CO2 emissions are captured and stored.

Cities

Urban carbon sequestration is also gaining attention. This involves enhancing green spaces in cities, such as urban forests and parks, which can absorb CO2. Green roofs and vertical gardens are other innovative ways to sequester carbon in urban areas.

The study is published in the journal Proceedings of the National Academy of Sciences. 

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