Dear Dr. Universe,

How do trees help the air?

— Ella, 12

Take a big, deep breath. As you inhale and exhale, you can probably feel the air taking up space in your lungs.

The air we breathe is made up of a few different things. It includes gases, such as nitrogen, oxygen and carbon dioxide — just to name a few. Animals breathe in oxygen and breathe out carbon dioxide. But in the plant world, it’s the opposite.

Trees, plants and even algae in the ocean, take in carbon dioxide from the air and, using the energy of the sun, transform it into the oxygen we all breathe. That’s what I found out from my friend Kevin Zobrist, a forestry professor at Washington State University.

Zobrist told me that process is called photosynthesis. It’s the way plants recycle carbon dioxide while also making their own food and energy.

Sometimes particles get mixed into the air that aren’t very good for us. They are so small we can’t see them, but they can sometimes irritate people’s airways or create health problems.

The good news: Trees are really good at helping catch and filter out these particles from the air.

Scientists have also found that trees with leaves that have tiny hairs on them are especially good at grabbing onto some of those particles and removing them from the air. I also discovered that some trees also capture particles in their bark, so animals like us don’t have to breathe them in.

It’s really important to have clean air to breathe. After all, the average human will inhale and exhale about 7 or 8 liters of air every minute or so. That adds up to each person breathing about 11,000 liters — or about 2,905 gallons, think milk jugs — of air each day.

Trees can also help cool the air. When it warms up outside and water from the surface of the leaves evaporates, it can take some heat out of the air. Meanwhile, trees can help capture dust and even smoke from wildfires.

While trees help store a lot of carbon within themselves, that doesn’t mean they can store it forever. When trees burn during wildfires, they release carbon dioxide back into the atmosphere, along with lots of harmful smoke particles. Trees help the air, except when they are on fire, Zobrist said. Carbon dioxide also comes from burning fossil fuels, such as the gasoline we put in cars. Climate change is a big problem from having too much carbon dioxide in our oceans and air.

For the most part, trees do their best to help the air stay cool and clean. They also make a great shady place to take a nap. You know, I think I’ll go find a nice spot to relax under a big tree. Thanks to your question, I will be reminded how important it is to take care of the trees that also take care of us all.

Have a science question? Ask Dr. Wendy Sue Universe, WSU’s resident science cat and writer, by email at Dr.Universe@wsu.edu, on her website at askDrUniverse.wsu.edu, via Twitter at @AskDrUniverse or at facebook.com/AskDrUniverse.

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