Microplastic Pollution Affecting Plant Photosynthesis

Microplastics Are Messing with Photosynthesis in Plants

By Joanna Thompson edited by Andrea Thompson

Microplastics are now a ubiquitous part of our daily physical reality. These minuscule fragments of degrading plastic now suffuse our air, our soil, the food we eat, and the water we drink. They’re being detected everywhere researchers look, from Antarctic sea ice to human brains.

As scientists develop a better idea of where microplastics are accumulating in the environment, they’re just beginning to understand how these pollutants affect one of the most essential and widespread kingdoms of life on Earth: plants. A new study, published on Monday in the Proceedings of the National Academy of Sciences USA, reveals how microplastics hinder photosynthesis across a wide range of plant species—including crucial food crops. “It’s really scary,” says Marcus Eriksen, a marine scientist at the 5 Gyres Institute, a nonprofit plastic pollution research organization, who was not involved in the study.

The researchers found that the presence of microplastics (plastic particles that are less than five millimeters in size) can reduce photosynthesis by as much as 7 to 12 percent, on average. That could range from 6 to 18 percent in terrestrial crops, 2 to 12 percent in marine plants such as seaweed and 4 to 14 percent in freshwater algae. “The exposure to microplastics was not surprising at all,” Eriksen says. “What surprised me was the level of impact.”

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A generalized reduction in photosynthesis at such a scale could have major implications for the global food supply, according to the study’s researchers.

With the current rates of worldwide plastic production (and resulting microplastics exposure), farmers could see a 4 to 13.5 percent yield loss per year in staple crops such as corn, rice, and wheat over the next 25 years. Additionally, seafood production could drop by up to 7 percent as aquatic ecosystems lose the algae that form the base of their food webs. This would seriously impact the global economy and exacerbate food insecurity for hundreds of millions of people, according to the study’s authors.

Decreased photosynthesis could also hamper efforts to fight climate change. As plants photosynthesize, they draw carbon dioxide from the air into their tissues and store it in the form of sugars. Most climate models assume plants will be able to take up atmospheric carbon at a consistent rate over the next several decades. But if less carbon is sequestered in forests, grasslands, and kelp beds than researchers had predicted, that will make mitigating warming that much harder.

Beyond photosynthesis, microplastics have been linked to health issues in humans and other animals. They are associated with an increase in people’s risk of heart attack and stroke, and they have been found to hamper growth and reproduction in a number of species.

The new paper further highlights the need for a global treaty on plastic issues, says marine biologist Richard Thompson, who specializes in microplastic pollution at the University of Plymouth in England and was not involved in the new study. Its team estimates that reducing the amount of plastic particles currently in the environment by just 13 percent could mitigate photosynthesis loss by 30 percent. Efforts to develop an international agreement on plastic have been underway since 2017—but the latest United Nations–led negotiations, held in Busan, South Korea, ended without a resolution.

Still, Thompson says, it is crucial to keep trying, especially as large chunks of plastic in the environment continue to degrade into microplastics. “If we don’t take action now,” he adds, “within the next 70 to 100 years, we’ll see much more wide-scale ecological harm.”