Arborists on Long Island have been concerned for decades that a truly powerful storm would wreak havoc on local trees. The island, and much of the northeast, had been largely spared the effects of catastrophic storms since 1985, when Gloria caused significant damage and flooding. Powerful storms cull weak, diseased, and structurally deficient trees, and the longer an area goes without a major storm, the higher the number of vulnerable trees. Over the past two years, Irene, Sandy, and most recently, Nemo, have confirmed the worst fears of tree professionals. I spoke recently with Bill Aitken, a licensed arborist with the Davey Tree Company of Nassua County, about the impact of storms on trees, and what homeowners can do to prevent or mitigate damage to – and from – their trees.
Aitken told me that he and his fellow Long Island arborists are still dealing with the aftermath of Sandy, and likely will be for months to come. Even these seasoned professionals were surprised by the number of otherwise healthy trees – especially oaks, but also lindens and pears – that were uprooted by the storm. All of these genera tend to lose their leaves very late in the season, which adds to the "sail" effect produced when heavy winds encounter a thick leaf canopy.
The best way to prevent uprootings and failures – breakage of trunks or branches – is through regular inspection and maintenance. Judicious and skillful pruning can leave the canopy – the outermost layer of branches and leaves – relatively open, which lowers wind resistance, increases light penetration, and provides better air circulation for the prevention of disease. Periodic examination for decay and internal damage can identify at-risk trees, including those that have become infested with carpenter ants. These ants live underground, and can enter a tree without leaving external signs of their presence. One oak that fell on a house during Sandy had a diameter of nearly five feet, of which only a six-inch band was sound wood. The rest had been reduced to spongy pulp by carpenter ants. Aitken uses visual inspections, tapping, and a device called a resistograph to locate damage that is invisible to casual inspections.
Aitken and his fellow arborists must walk a fine line when it comes to advising their clients on which trees to remove. Some homeowners, understandably spooked by the ravages of recent storms, want all trees within range of buildings removed. The visual effects of this type of clear-cutting can be almost as devastating as actual storm damage. In other cases, property owners will opt for a tree-by-tree evaluation, removing only those trees that are obviously at risk for failure or uprooting, or whose location is so compromising that the risk of any accident is unacceptably high.
I'll relate Aitken's advice on recovering from a storm, arboreally speaking, in a subsequent article.