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Why do forests smell so good?

By David, 13 September 2018 News

Image of light filtering through the trees.

Can you smell the air? Image: ©istock.com/keiichihiki

There’s nothing quite like the smell of a forest. But the trees aren’t making these smells for your benefit. There’s got to be something in it for them – but what?

The chemicals that make up a forest’s smell are volatile organic compounds, or VOCs. And smelling nice is not all these VOCs are good for.

These chemicals scatter light – taking harsh beams coming straight from the Sun and turning them into a softer glow that fills the forest. Leaves that normally would be in shade end up getting at least a little bit of light, and overall, trees get more energy to grow.

Well, that’s the theory, anyway. To test the idea, a group of British scientist turned to computers. They set up calculations to work out how much effort it would take to produce these VOCs, and how much extra energy the forest would harvest as a result.

In the end, the team calculated that VOCs helped a forest grow. The light scattering benefits more than outweighed the cost of releasing all those chemicals.

So next time you walk through a forest, enjoy the smell. You know the trees are enjoying it too!

Volatile organic what?

Wondering how volatile organic compounds got their name?

In common language, volatile means unstable or even likely to explode. But, to chemists, a volatile chemical typically evaporates around room temperature.

In this case, organic means the chemicals are based around carbon atoms, just like most chemicals in living things.

A compound is a chemical that is not all one element. That means there are other, non-carbon atoms in each molecule of VOC.

Most smells come from VOCs, which can be naturally occurring or made by humans. They can be helpful or harmful.

There are some VOCs that are famously dangerous. Paints, glues and car exhausts all contain harmful chemicals that evaporate around room temperature, are based around carbon and contain a range of other elements. For this reason, scientists are working on reducing the amount of these VOCs in our cities.

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