Trees don't live forever and can become a hazard
Sometimes when talking with young students, I like to ask them if trees live forever. Many kids think they do. Maybe some adults do too, since trees may appear to be living in one spot seemingly unchanging for many decades.
In fact, trees, like we humans, do not live forever. Each of the various tree species normally live to a certain age before they start to rot and fall apart. When trees are growing in an urban setting, there are many more stress variables that often reduce their life spans. These trees also often become hazardous to people and property sooner than they would in a rural setting.
Few landscape features are held in such high regard, or prompt such fierce protectionist feelings, as a large mature tree growing in one’s yard. That is often the case even if the tree is diseased, decayed, damaged, insect infested, or simply at a point in its lifespan where it has begun to decline naturally due to old age. Trees, like all living things, have a finite lifespan; however, a tree may appear extremely healthy on the outside, and still reach a point where it has to be removed as a potential hazard to public safety. Nowhere is this more important than in urban settings where many people are nearby and moving about. Sometimes people have a hard time understanding, or admitting, that their big beloved tree is potentially dangerous and should be removed.
Many people naturally form strong personal attachments to trees and want to protect them. These feelings may arise from a sentimental attachment, such as a tree planted by, or for, a relative. It may be deemed special due to the homeowner valuing the many benefits provided by trees, such as environmental and aesthetic, or simply because it has always been there. There comes a point in time, however, when a person must know when to say when, and a decision to remove a tree must be made in the interest of their family and public safety. Again, a tree does not have to be dead or even dying to be hazardous.
The Truro Urban Tree Committee is responsible for removing known hazard trees within the Town of Truro, usually in mid-winter during freeze-up. To determine if a tree should be classed as a hazard there are three considerations to be considered: first, you must have a tree with the potential to fail; and all trees have the potential to fail. Secondly, are there conditions or other contributing factors which may help cause that tree to fail, such as old age, previous damage, decay, and leaning? Thirdly, and most importantly, the presence of a person or object which could be injured or damaged in the event of tree failure. The combination of these three elements help determine the severity of the hazard. For example, take two basically identical trees with identical structural defects which predispose them to fail. Place one tree in the middle of a forest stand on top of Nuttby Mountain, the other on Prince Street in downtown Truro. The tree growing in the middle of the woods on top of Nuttby is not a hazardous tree as it has no people around it on a regular basis that could be hurt. The one on Prince Street growing next to the sidewalk would be classed as hazardous and scheduled for removal.
Once a hazardous condition has been identified within a tree, some action should be taken to eliminate the hazard. The action taken will depend on the condition of the individual tree, degree of hazard, and the location and nature of potential “targets”. Corrective action could consist of eliminating/moving the target, hazard reduction pruning to remove the unsafe limbs or portions of the tree; installation of a tree support system, such as cable bracing or anchor bolts, or complete tree removal. Ideally, the hazard can be eliminated by removing the potential target and thereby avoid having to remove the tree. This is not a problem if your target is a park bench, picnic table, or even a baby barn. However, if your target is a public street or sidewalk, a building, or established utility lines, then it is obviously not practical to remove these targets, and the tree will have to be braced, pruned, or removed.
Another important consideration which must be addressed in evaluating a trees potential for failure, and one which seems to be increasing in importance as a result of climate change, is wind, winter storms and hurricanes. Ice or wet, heavy snow which sticks on trees, can act as the proverbial "straw that broke the camel's
back.” In fact, an accumulation of snow and ice can result in an increase in tree branch weight by as much as 30 times.
The cost of urban tree work is significantly higher than most people realize. It is not the same as going out to the back forty to fall a few trees for firewood. Arboriculture is a specialized field which is not at all comparable to commercial logging practices. Urban forestry work requires specialized training, knowledge, equipment, techniques, and considerations not typically utilized in conventional forestry operations. Conversely, most "arborists" are not "loggers,” and are not trained or involved in operational forestry. Forestry and Arboriculture both fall under the umbrella of plant science — they are related fields of study, but they are not the same.
Trees are very much a product of their environment. The overall health and vigour of a tree is most definitely influenced by the environment in which it is growing. The potential for its development may be predetermined largely by genetics, but the realization of that potential will be determined in part by its surroundings. An urban environment can be, and typically is, a very harsh and unforgiving location in which to live and grow. Just as people living in the city are exposed to many stresses and situations their rural cousins do not have to deal with, the same can be said for urban trees.
Urban trees must deal with a wide range of limiting factors such as: urban pollution; poor soils; compaction of the rooting zone from traffic and construction; limited/insufficient rooting space; limited growing space above ground; de-icing salt; disturbance to the root system as a result of street, sidewalk, sewer, and water work; radiant heat from adjacent buildings, asphalt, and concrete; mechanical damage from cars, trucks, snowplows, lawnmowers and line trimmers; unintentional herbicide damage as a result of "weed and feed" type lawn fertilizers; utility line clearance activities; vandalism; neglect; improper maintenance; insect infestations, and disease. That trees are able to live in an urban setting, let alone thrive, with all of the above going against them is truly nothing short of remarkable. But again, it must be stressed that being alive, and appearing healthy, does not equate to being nonhazardous.
The decision to remove a tree is never an easy one, nor something to be taken lightly. Trees in a state of decline, with large cavities, and dead standing trees (ie. "snags"), still provide many significant benefits to the environment in general. These benefits range from providing wildlife habitat for cavity nesting birds, animals, and insects; perches; sources of food for many insect eating creatures; large woody debris and organic material which will be returned to the soil as it decays, providing nutrients and improving soil structure, and food sources for many types of fungi and invertebrates found in the soil. If these trees in poor health are located in isolated locations, then they will continue to provide ecological benefits for many years. However, if they are located along sidewalks and streets, the hazard trees should be removed as soon as possible.
Once you realize that you are going to lose a tree, the logical thing to do is start planning what and where you would like to plant for replacement trees in the spring.