Study: Trees Break At Same Wind Speed Regardless Of Size or Species

170px-General_Sherman_tree_looking_upI read about a fascinating new scientific study where Emmanuel Virot and colleagues at the Ecole Polytechnique and ESPCI ParisTech have concluded that there is a critical wind speed, of around 42 m/s (90 mph), at which almost all tree trunks break – regardless their size or species. Thus, under a simple scaling law, the critical wind speed is largely independent of the tree’s diameter, height or elastic properties.

220px-1859-Martinique.webThat is so remarkably counterintuitive that it takes some effort to get one’s mind around it. The study does not look at tree loss due to uprooting. Rather, it focused on situations where the roots hold and there is a breakage. Some trees can break through torsion. However, most break through bending. The study looked at the bending breaks, which is referred to as “stem lodging”.

Looking at a 2009 storm called Klaus, the data showed the greatest damage to forests occurred in regions where the wind speed exceeded 42 m/s but also that it did not appear to vary on tree age and type. As an avid hiker, I find that incredibly surprising. I have seen a lot of bending breaks but always assumed that certain trees to more resistant to such loss.

In their modeling, the researchers doubled tree height but found that it increases the critical speed by only 9%. The elastic properties of the wood had a similarly small impact. That really puts serious question to the common expression that it is better to “bend than break.” It turns out that all trees break rather than bend at roughly the same rate. Go figure.

Source: PhysicsWorld

16 thoughts on “Study: Trees Break At Same Wind Speed Regardless Of Size or Species

  1. Another factor that I would think would be important is the “sail” effect, meaning the amount of wind that the tree and its leaves catch.

  2. That is so strange. You would expect a tree with deep roots, and a massive trunk, to be relatively resistant to breakage. Or one with a bendable, whiplike trunk to be more adapted to high winds.

  3. “…a critical wind speed, of around 42 m/s (90 mph), at which almost all tree trunks break – regardless their size or species.” This would seem to mean that hurricane winds of over 90mph would leave almost every tree broken. States like Florida would be essentially stripped of trees. Since this doesn’t actually happen, I would question the study.

  4. We had 60mph winds during an El Nino storm a couple weeks ago in San Diego. Eucalyptus trees seemed particularly vulnerable. A large tree fell not far from our house, killing a young woman in her car. She was a vivacious person, a drummer in a band on her way to a gig.

  5. Man, I would have to read the study. There are variables that pop out to the engineer in me and which are not discussed as having been considered. Looking “back” (I think they call that epidemiology) at what happened, as opposed to submitting trees to conditions that are controlled, allows for error in the analysis.
    I would be very skeptical of accepting this without reading the actual study.

  6. As I read the post and some of the comments, may I suggest that it is the wind speed experienced by the tree, not necessarily the measured wind speed of the storm. A tree in a group has the wind flow pertubated – reduced- by the others. The moment a change of direction resulting from an encounter with an object is a moment of reduced energy…speed. Think buildings and topography. Not addressing the Venturi effect here.

    There is also a pressure wave countering the wind when a group of trees or other things is bunched, as it were. Ever ridden the draft of a large truck? It’s also an experience to ride the wave coming off the corner up front of a large truck.. Need cooperation, a CB radio and a long straight freeway without “bears”. Youth (the crazies) is “helpful.” Note that both vehicles have equal ground speed.

  7. My experience is that it depends on the foliage on the tree. We had a pine tree fall on our house during a hurricane which had winds close to 90mph. We ran from the storm because we had an old oak tree that I was sure would crush our house. That stood, yet a pine tree in our neighbors lot fell and hit us. I finally figured out that the reason the oak stood was that it had little foliage and what it had was dispersed over a large area.

  8. Disciple Caine: Master, do we seek victory in contention?

    Master Kan: Seek rather not to contend.

    Caine: But shall we not then be defeated?

    Master Kan: We know that where there is no contention, there is neither defeat nor victory. The supple willow does not contend against the storm, yet it survives.

    Master Kan: Avoid, rather than check. Check, rather than hurt. Hurt, rather than maim. Maim, rather than kill. For all life is precious, nor can any be replaced.

  9. Some forest in the path of a single storm appears to be the subject of the study, so I would guess the range of tree species may have been rather narrow.

  10. Americans…. Always doubting the science. It was a cold day in December in Miami so climate science is bunk. It’s just ‘weather’ as The Donald will tell you. I drive my gas sucking truck 50,000 miles a year and I don’t see any climate impacts, so fossil fuel use doesn’t have a bearing on climate change. Just ask ExxonMobile. They told you for 40 years that fossil fuels do not affect climate until they were shown to have lied. My uncle lived to 90 years old and smoked like a chimney, so smoking doesn’t cause lung cancer. The flick ‘Thank you for Smoking’ comes to mind. I saw a storm in Florida and not all the trees broke, so I doubt the validity of the study.

    KISS. Keep it simple stupid is how Americans are treated by their overlords, since they know most Americans are unable to handle much in the way of analysis. Build a wall and have Mexico pay for it. Carpet bomb the Middle East. More brutal torture more often. Guns for everyone everywhere! Drill, baby, drill. Comsequences? There aren’t any! Amazing….

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