First published on Apr 19, 2013
Trees make noise when they are thirsty.

Drought stressed trees emit sounds according to scientists from Grenoble University in France.

Arborists have suspected this for a while but just recently found a means for validating the theory.

Trees drink by absorbing ground water through vein-like structures called xylem.

When the supply is short they have to work harder to pull up water. The stress of the process can cause the water stream to rupture and produce air bubbles.

Too many air bubbles can lead to the death of the tree.

To confirm their suspicions that the process has an acoustic signature the researchers placed a mocked up tree piece in a capsule of gel.

By removing the water from the gel they found that about half of the sounds made by trees are due to their drinking process.

The scientists believe that in the future foresters could use acoustic detectors to locate stressed trees and avert permanent damage.

People have been listening to trees since the late 1960s when a Scottish scientist plugged a pair of headphones into one.

The internal noises they make are mostly inaudible to the naked ear.