Why Do Some Trees Scream When They Dry Out?

Imagine you are drinking a thick milkshake with a straw. If the straw gets too narrow or clogged, you have to suck harder. That hard sucking makes a quiet pop inside your mouth if it is sealed tight. Trees do something very similar! When there is not enough rain, trees struggle to pull water up from their roots. This creates tiny bubbles of air in their tubes, which make popping sounds.

Trees have long, thin tubes called xylem that act like straws. These tubes carry water from the soil to the leaves. When it is dry and hot, the tree pulls on this water like a straw pulling up a drink. Sometimes, the pull is so strong that tiny air bubbles form inside the tubes. This event is called cavitation.

These bubbles burst with a sound wave, much like ice cracking in a glass. The sounds are high-pitched clicks and pops. They happen so often during a hot summer day that researchers can record them on sensitive microphones. While we cannot hear the tree screaming without special equipment, scientists say it is a clear sign of thirst.