March 23rd, 2012 by

By Michelle Werts

Lightning near trees

Credit: Larry Johnson/Flickr

Lightning likes trees. No surprise, right? It’s something we’re taught as kids: Lightning seeks the path of least resistance to the ground, and tall objects, like trees, help it get to the ground faster. Well, as it turns out, there might be more at play here than just a tree’s magnificent height.

According to new research published in the journal Environmental Science & Technology, scientists in Australia have discovered that the air around trees is electric. Literally. In the study, measurements were taken at six locations around Brisbane of the ion concentrations — the atom or molecule that gives off positive or negative electrical charges — in the air. They found that ion concentrations in heavily wooded areas were double those in areas of grassy fields. Why is this the case?

Natural ions enter the atmosphere in two primary ways: from cosmic radiation and from radon gas. And, it’s posited that the trees factor big time into getting radon into the atmosphere. Time for a chemistry/geology/biology lesson: Radon comes from the radioactive decay of radium, which is found in rocks. As the radium in rocks is converted into radon underground, the water in the soil absorbs the radon. The trees suck up this water, which then evaporates through their leaves. In one day, one large tree can lift up to 100 gallons of water out of the ground and discharge it into the air. Voila, more radon with its ions in the air.

The authors of this study also believe that trees with the deepest roots are also the ones that bring the most radon into the atmosphere. They suggest that a eucalyptus forest might produce up to 37 percent of the surrounding area’s radon at times. That’s a lot of electricity!