Plants can be better at fighting climate change. A stone garden shows that ozone is holding them back.

Unlike most gardeners, Danica Lombardozzi does not want tomatoes and pumpkins in late summer. At the National Center for Atmospheric Research, a climate scientist will instead test the “ozone garden” for coffee and black dots.

“By the end of the growing season in Colorado, the damage will be severe,” she said. This is a little scary for me because it means a lot of ozone.

The garden is located on the hills above Bolder, Colo, near the entrance to the NCAR Mesa Laboratory. On a hot, mild September afternoon, Lombardozizi visited to collect information on plant damage, which was not difficult to obtain. Large areas of some dairy products are blackened. A careful look at the Rocky Mountain leaves reveals a matrix of brown dots.

Each diseased plant hinted at bad weather in the region. Along with wildfires, the region has seen an increase in ground-level ozone. The complex chain of chemical reactions creates invisible pollution when heat and sunlight hit many other pollutants. The small garden is filled with ozone-sensitive species known as biodegrators so that people can see the obvious evidence of the problem.

Kevin J. Beatty / Denver
Ozone damage to leaves growing in an ozone garden outside the NCAR Mesa Laboratory above Boulder. September 8, 2021

Plant beds are more than just a place for public visits. It is part of a national network of similar plots to help scientists understand how ozone harms plants – and one of the planet’s best natural defenses is climate change.

To understand the relationship, Lombardozzi said it was important to focus on the role of carbon dioxide. Since the beginning of the Industrial Revolution, fossil fuels have emitted greenhouse gases into the atmosphere. As gas storage in the atmosphere increases, so does the planet’s average temperature.

Fortunately, plants rely on the same gas for photosynthesis. As a result, estimates suggest that fossil fuels will reduce the impact of greenhouse gas emissions by about one-third of all fossil fuels over the past decade.

“It does a wonderful job of protecting our climate,” says Lombardozzi. They take carbon dioxide from the atmosphere and store it in their leaves.

The problem is that just as it disturbs the human lungs, ozone irritates the airways of plants. At the base of all the leaves there are tiny holes called stomata, which carry contaminants. Once inside, a single oxygen atom, called a radical, breaks down a large ozone molecule and irritates the cell membranes in plants.

Kevin J. Beatty / Denver
Ozone garden outside NCAR Mesa Laboratory above Boulder. September 8, 2021

To save himself, the plant closes the stomatal. Lombordozi said the process harms individual plants in the garden and makes it difficult to remove carbon dioxide from the atmosphere for all forests and lawns.

It also means that plants can be more effective carbon washers. A 2020 study found that a 50 percent reduction in ozone depletion in the transportation and energy sectors would increase plant photosynthesis enough to regenerate carbon dioxide. Researchers have found that 15 percent more plants can block greenhouse gases if humans completely eliminate the ozone depletion problem.

Why is the stimulant in her garden so low? The damage to a partner that is crucial to climate change is that people can probably heal wounds.

“It’s a double beat,” she said. “If we reduce ozone emissions, we can breathe more easily and our plants can store more and more carbon, which is helping us reduce carbon dioxide in the air.

Kevin J. Beatty / Denver
Ozone garden outside NCAR Mesa Laboratory above Boulder. September 8, 2021


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