Evaluating the hazards posed by trees
My last two columns on burning wood and the hazards of breathing wood smoke generated more email than almost anything else I have written in a long time. I could not understand why I was getting emails from places as far away as South Dakota, until someone told me the last column was uploaded to Facebook. Never underestimate the power of the press, especially when it is connected to the Internet and it surely is.
This week, I will discuss a topic that is a bit less controversial.
Winter is a good time to look hard at the deciduous trees in your landscape when the distracting camouflage of the leaves are gone. As a certified arborist, working for Cornell Cooperative Extension for more than 30 years, I had the not-so-easy job of evaluating hundreds of trees over the years to determine if they presented a hazard to people or property.
When looking at street trees in the community, this often became a lose/lose situation. Typically, someone would call the county, town or village worried that the tree near their house presented a serious hazard. In many cases, the offending tree was of great value and affection to the nearest neighbor. While neighbor “A” was worried that the tree was going to fall apart some windy morning and kill their kid waiting for the school bus, neighbor “B” loved the tree dearly for its majestic beauty and all the shade in the summer it provided their house.
Old, stately trees are indeed beautiful and often become even more beautiful as they age, as most people will acknowledge. I wish most people felt the same about old people, such as I have become.
The first step in evaluating any tree is learning what the species is. The simple fact is that certain species of trees are far more likely to become hazards than others. This common sense notion is actually a surprise to many people. All tree species are sometimes considered as pretty much equal, particularly when urban planners are designing the layout of street trees, but that is certainly not the case.
It is true that even the softest and seemingly weakest of woods, for example balsa wood, can be used to support the heaviest of loads when the wood has been cut into boards and the engineering principles of support have been properly worked out. I know
that Popsicle sticks can be used to assemble a structure that can support hundreds of pounds, many thousands of times the weight of the sticks themselves, but trees are living entities and not just big hunks of wood. Trees are engineered by nature, not by humans.
In order for a tree to present a hazard, it must be located where its collapse will damage people or property. That big, old pine tree on the far end of your 5 acre property may indeed fall down, but, unless there is a good chance it will fall
on something important, it is not a hazard.
Street trees are a different story, of course. Whoever decided (100 years ago) that silver maple trees would be great street trees made a serious mistake! As they age, they drop many dead branches and their roots lift sidewalks that need to be reset every few years.
It is generally true that the most-rapidly growing trees are also the weakest-wooded and have the shortest life span. Species such as poplars, willow, black locust, red maple and silver maple can grow 6 feet in a single season once established, but these trees often begin
to decline and die after 30 or 40 years.
Susceptibility to pests, diseases or adverse environmental conditions also shorten the life span of many tree species. Sugar maples have been widely used as street trees, but they are very susceptible to salt damage and rarely live to 150 years as they would in a forest environment.
Next week, I will continue with this topic and teach you what the warning signs are that a tree may become a hazard sooner than later.