As temperatures rise, so does air pollution from plants. And the researchers warn that this will seriously affect air quality.

When you think of air pollution, you might think of culprits like industry or fuel-powered cars. But plants also play their part, emitting chemicals called “biogenic volatile organic compounds.” “The smell of fresh grass or the sweetness of ripe strawberries: these are vital VOCs,” said researcher James Gomez. “And plants emit it constantly.”

Health problems
The substances are not harmful by themselves, but once they interact with oxygen they generate organic aerosols. It can lead to health problems. For example, they are linked to heart disease, lung cancer, and asthma among children.

He increases
The emission of these biogenic volatile organic compounds appears doomed. Plants increase their emissions when the concentration of carbon dioxide increases and when the temperature rises. Both are on the agenda due to anthropogenic climate change.

Plants and fabrics
But how much will this affect air quality? Researchers are now looking into that. Their results can be read in the journal Earth and Environment Communications. For the study, they looked not only at air pollution caused by plants, but also at another natural phenomenon that affects air quality, desert dust storms. These are also expected to increase in the coming years. “Our models predict that increased winds will lift more dust into the atmosphere,” said researcher Robert Allen.

Fine dust
Both vital volatile organic compounds and dust blowing from the desert onto large parts of the Earth can be considered particulate matter (with a diameter of 2.5 micrometers or less, or PM2.5). The research by Allen and colleagues reveals that these particulate matter from natural sources increases as much as carbon dioxide concentrations in the atmosphere. “The more carbon dioxide we put into the atmosphere, the more PM2.5 is put into the atmosphere,” Gomez said. In concrete terms, this means that if we put so much carbon dioxide into the atmosphere that the climate warms by 2 degrees Celsius, the amount of PM2.5 will increase by 7 percent. And with a 4-degree increase in temperature — which we could easily reach in the year 2100 without a quick and hard intervention — even the researchers predicted an increase in PM2.5 of 14 percent.

Natural sources only
Just to be clear: This increase is only related to emissions from natural sources, like vegetation and dust storms. This is because the study does not look at simultaneously increasing and man-made air pollution, which has already been the subject of several previous studies. “We don’t look at human emissions of air pollutants because we can change what we emit,” Gomez explains. “For example, we could start driving electrically. But that might not change the air pollution from plants or dust.” The only way to reduce those emissions is to reduce our carbon dioxide emissions. “The lower we go (and he is, ed.), the better the air quality becomes.”

Keep your garden alive
Anyone who finds air pollution from plants a little scary might be tempted to fill their front and back gardens with tiles anyway. No, the researchers say. Because though this study may seem like it’s painting plants in a bad light, scientists know we really need it. Also in the fight against climate change. Plants absorb carbon dioxide and thus reduce the concentration of carbon dioxide in the atmosphere. However, the problem is that we are putting so much carbon dioxide into the atmosphere that plants can’t compete with it and the concentration of carbon dioxide increases anyway. But this increase would be greater if we did not have plants. In addition, it is not the case that the borders or the lawn in and of itself have a major negative impact on air quality and therefore our health as well. “Your garden, for example, doesn’t produce enough vital volatile organic compounds to make you sick,” Gomez points out. “It is the large increase in carbon dioxide that contributes to the biosphere producing more VOCs – and therefore more organic aerosols.”

And so we expect to see a significant increase in those organic aerosols. An increase that may be much larger than researchers currently expect. Because, Gomez argues, the predictions made in the new study may be a little conservative. “For example, we also did not include climate change-induced changes in wildfire emissions.” And while reducing our emissions – and thus reducing the concentration of carbon dioxide in the atmosphere – can provide solace, very strong action is needed if we are to see positive effects on air quality in the future. Gomez is not optimistic about that. “Make sure you get an air purifier ahead.”