Why Do Trees Have a Deep Sleep at Night?

Think of a tree like a busy factory that never sleeps. During the day, it is very active. It uses sunlight to make food from air and water. This process gives out fresh oxygen for us to breathe. But what happens when the sun goes down? The factory does not shut down completely. It just changes its job.

The tree still needs energy to stay alive. It burns up some of the food it made earlier to keep its roots and leaves working. This burning process takes in oxygen and gives out carbon dioxide. During the day, the tree makes so much oxygen that the extra carbon dioxide disappears quickly. At night, there is no sunlight to help make new food. So, the tree looks like it is breathing out more than it breathes in.

This means forests are actually contributing to warming slightly at night. However, this effect is small compared to how much carbon trees store over their whole life. They are still our best friends in fighting climate change.