It takes a volcano or a nuclear explosion to bring down a forest of trees, but a thunderstorm or snowfall will uproot trees in your neighborhood. Hurricane Sandy toppled over 8,000 trees in New York City, and thousands of others elsewhere. But many stayed put, so what causes one tree to fall and another to survive? Author Mary Knudson asked plant physiologist Kevin T. Smith, arborist William E. de Vos, and other experts.
The answer from Smith is not very comforting: “The first thing to know is that all trees have the potential to fail at some level of force from wind, snow, ice, either singly or in combination,” he says. One main reason, all three experts agree, is the phenomenon known as “windthrow” which uproots a tree. “The tree trunk acts as a lever and so the force applied to the roots and trunk increases with height,” says Foster. “Taller trees are more susceptible to windthrow.”
“The roots of trees can extend 1-2.5 times the radius of the branches and many urban areas do not allow this extensive development,” answers de Vos . “The problem lies mostly with trees that have been developed around and had roots cut, crushed or torn in the process. There may be ensuing decay.”