Article 11 of 12 from Trees: Dispelling Myths & Misinformation, prepared by the arborists of the Southwest Division of Bartlett Tree Experts as a community education initiative.
Asked by a property owner to meet with a building contractor about tree protection, an experienced arborist could tell the contractor didn’t take seriously the need to protect trees during the project. “I’ve been doing this work for thirty years, and I haven’t killed a tree yet,” the contractor bragged.
How would he know? For some trees, it can take a few years to exhibit the effects of construction damage and maybe a decade or so to die from it. By then, the contractor is long gone, and nobody makes the connection. This is, in part, what has made it so difficult to convince decision makers that planning, implementing, and enforcing tree protection at construction sites is critical, whether it’s a commercial or residential site. But some businesses and communities are taking this process more seriously, and it’s a pleasure to work with them in the interest of preserving trees for future generations. Let’s look at some issues that will help property owners understand the need for a qualified arborist as part of the construction team.
Far too often, an arborist is called into a project after damage has occurred. The task becomes remediation instead of protection, and this is always more costly in the long run, especially since the tree is more likely to die anyway as a result of the damage.
Sometimes, an impressive tree-protection plan gets developed with the help of an arborist. The plan then helps secure the building permit, but no enforcement is required as part of the permit process. The trees suffer damage, exhibit symptoms of decline in the years that follow, and die prematurely. No one makes the connection.
Protecting the Critical Root Zone (CRZ)
A good plan will specify that a chain-link fence (harder for workers to move out of the way) be installed around the tree to protect the CRZ (typically from the trunk to the drip line). Here are a few examples of what often happens if the fence is not there:
- pile fill and debris over the root system and against the trunk.
- drive vehicles and equipment over the CRZ and park on it.
- mix mortar, paint, and other materials over the CRZ.
- cut utility trenches into the CRZ
- store building supplies on the CRZ
- create elevation changes on or near the CRZ
Not only do many of these activities compact the soil, they introduce chemical changes to it, create possible drainage problems, cover the root crown and root system, sever major portions of the root system, tear major roots that exposes them to decay, and create the potential for structural instability.
In addition to the CRZ, other protection measures include any needed pruning for health, safety, or vehicle clearance; providing moisture to the trees; and fertilization and pest management to bolster the tree’s resistance to stress.
More and more communities are implementing systematic tree protection requirements for construction projects, and they are employing urban foresters to assist with planning, enforcement, and aftercare. Protecting trees at construction sites really matters. Not doing it can take years off the life of a tree.