Plants are working harder to combat air pollution, study finds. But is it enough?



Alison Cutler
Fri, December 10, 2021

Plants could be the world’s universal currency to buy time against climate change, but will it be enough? A recent study from the Lawrence Berkeley National Laboratory in California found that plants are working harder to offset growing carbon emissions across the globe through high levels of photosynthesis.

It’s a good sign, researchers said in a news release about the study, since it helps understand ways to mitigate carbon emissions, but it’s not powerful enough to halt climate change.

The observational study, which was published in Nature on Dec. 8, used “terrestrial biosphere models” and estimates of the natural carbon cycle to evaluate the response of photosynthesis to carbon through history. Then, researchers used previous separate reports on the relationship between carbon and photosynthesis to decipher changes.

According to the researchers, plants are photosynthesizing, where they “suck carbon dioxide from the air and produce their own food,” at a rate 12% higher than they were between 1982 and 2020. During that time period, global carbon dioxide concentration in the atmosphere swelled by about 17%, the study indicated.

“This is a very large increase in photosynthesis, but it’s nowhere close to removing the amount of carbon dioxide we’re putting into the atmosphere,” Berkeley Lab scientist Trevor Keenan, lead author of the study, said in the release. “It’s not stopping climate change by any means, but it is helping us slow it down.”

There are certain challenges that come with measuring photosynthesis across the globe, the study pointed out, including weighing the photosynthesis rates of brush land versus large forests, and relying on specific methods of observation, including satellite observations or proxies, to determine an outcome.

While satellite images can tell researchers how much green is covering a mass of land and estimate the amount of leaves and plants that are contributing to the photosynthesis process, it might not account for the heightened photosynthesis process caused by carbon emissions, according to the release.

By using previous reports and determining which observations used overly-sensitive and under-sensitive estimates of carbon emissions on photosynthesis, the team was able to come up with a number.

“Our estimate of a 12% increase comes right in the middle of the other estimates,” Keenan said in the release. “And in the process of generating our estimate, it allowed us to re-examine the other estimates and understand why they were overly large or small. That gave us confidence in our results.”

The team used previous reports from the Global Carbon Project to flesh out the history of carbon emissions and its impact on photosynthesis.

According to recent data from the project, the world saw a record drop in carbon emissions during 2020, falling by 5.4%. In 2021, however, the use of coal and gas outgrew it’s drop from the year prior, and carbon emissions are set to rebound to 4.9%, the Global Carbon Project predicts.

Given that carbon dioxide lingers in the air for longer periods of time than other greenhouse gases, researchers from Berkeley Lab said it was critical to examine how it would be possible to offset the consequences of rising air pollution rates.

Keenan also added that researchers weren’t sure how long the higher production of photosynthesis in relation to growing carbon emission rates would last. At some point, Keenan said in a release, it could saturate.

“We don’t know what the future will hold as far as how plants will continue to respond to increasing carbon dioxide,” Keenan said.