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Dr. Universe: ‘How do trees give us air to breathe?’

An upward view of several treetops in a forest.
Forests provide a “carbon sink” that absorbs a net 7.6 billion metric tonnes of CO2 per year, 1.5 times more carbon than the United States emits annually.

In recognition of Earth Day, the WSU Insider dug into the Ask Dr. Universe archives for a 2021 piece answering a question from a curious 11-year-old about how trees give us air to breathe. 

The fictional feline Dr. Universe sat down with her friend Balasaheb Sonawane, a WSU biologist, to learn about how plants use energy from the sun to make oxygen via a process called photosynthesis.

Sonawane explained that plants don’t have a nose or mouth like humans but rather use tiny microscopic organs on their leaves called stomata to move gasses in and out. Another key difference between humans and plants is that while humans breathe oxygen gas, plants take in carbon dioxide gas using the stomata on their leaves.

During photosynthesis, plants use energy from the sun to make sugar from the carbon dioxide they absorb through their leaves. When this happens, water molecules break apart and form oxygen molecules—the air we breathe.

Plants need carbon dioxide to do their work, but now there is too much carbon dioxide in the atmosphere and it is contributing to climate change. Researchers at WSU are working hard to address the effects of climate change and you can too. Instead of taking a car that releases carbon dioxide, you might walk or ride a bike when you can. We can also plant more new trees on the planet.

Visit the Ask Dr. Universe website for answers to more questions from curious elementary and middle school students.

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