Dealing with Tree Risk: Tips for Municipal Shade Tree Commissions

Shade Tree Commissions are charged with protecting the trees that line a community's streets and parks, but they must also remember that the municipality has an obligation to maintain a safe right-of-way. To achieve both goals, without clearcutting the urban forest to avoid failing trees and litigation, shade tree commissions need to develop a system by which we detect and deal with declining, high-risk trees. The following are some tips to help keep your community's trees safe.

Inspect Your Community Trees on a Periodic Basis

An early spring inspection before the leaves come out will help find dead, broken, decaying and structurally defective branches in the canopy of the trees. Even a drive-by inspection by trained and knowledgeable tree commissioners or public works staff is extremely helpful. A follow-up inspection could be completed in late summer to help distinguish branches that are alive (in leaf) and those that are dead. Inspections after major storm events (summer thunderstorms or winter ice) will help find broken "hangers" on live trees that could fall without warning weeks after a storm.

Complete an Inventory

Knowing what types of trees are present, their size, and their condition is very helpful for planning the work that needs to be done each year. It will also tell us where the trees are located that are declining in health and should be periodically inspected or removed if they pose a high risk. The inventory data will help the community prioritize the work and provides excellent documentation should they become involved in litigation. A community with an inventory and scheduled work plans, illustrates prudence and can help argue against claims of neglect should a tree or branch fall and injure people or damage property.

Inspect Individual Trees of Concern

Individual trees found to be of concern in inventories or drive-by inspections should be inspected in detail. Inspections should always be documented in writing whether the trees are considered defective or not. When inspecting trees, written documentation should include the date of inspection, the inspectors name, defects noticed, and recommended treatments. It is good to develop a standardized form that can be used for each tree or use the Basic Tree Risk Assessment Form developed by the ISA. Forms can be paper or in a digital format on a phone or tablet. If using paper forms, make sure they are scanned and stored digitally.

Removing a Dangerous Situation Does Not Always Mean Removing the Tree

Sometimes risk is limited to parts of the tree. In some cases, pruning large deadwood is all that is needed to mitigate risk. Risk can also be mitigated by moving targets, such as picnic table in a park setting, away from a defective tree.

Managing tree risk around this park picnic shelter does not require removal of any trees, but can be achieved by periodic inspections and pruning to remove deadwood from what are otherwise structurally sound trees. Photo: Brian Wolyniak, Penn State Extension

Obtain Training for Your Inspectors

To determine whether a tree is a high risk, inspectors must understand what to look for, such as deadwood, cracks, decay, cavities, included bark, and fungal fruiting structures. They must also understand CODIT (compartmentalization of decay in trees) as well as the characteristics of the species they are examining. For example, sugar maple and oak compartmentalize decay (walling it off) much better than species like silver maple and poplar. The International Society of Arboriculture (ISA) provides a Tree Risk Assessment Qualification (TRAQ) for Certified Arborists to learn and obtain the credentials to inspect trees. Even if your inspections are being completed by shade tree commission members or municipal staff, some training is critical so that defects are not missed in the field.  

Bring in Professional Arborists When Tree Condition and Risk is Unclear

Some trees are "no-brainers." They have so much deadwood, or the tree is completely dead, deciding to remove it is quite easy. Other trees might look very healthy with lots of green foliage in the canopy, but they have major structural defects or fungal fruiting structures at the base of the tree. A Certified Arborist that is TRAQ trained and qualified should examine the tree closely. The arborist should be hired as a consultant to the municipality to assess tree risk. They should not be the same arborist that will be bidding on the removals of the trees. This will avoid any conflicts of interest. It is best if the tree commission can produce a list of trees from their inventory or inspections that the TRAQ consulting arborist can review in the field and provide a detailed report and prioritization of removals or pruning. That prioritization of work is very important because most municipalities have limited budgets to remove or prune trees. They will have to work on the worst trees first and having documentation is important as they proceed down the list over time as budgets allow.

Systematic Inspection and Prioritization of Work is Important

Try to keep politics and emotions out of the decisions to remove or keep a high-risk tree. It could be the oldest tree in town, but if it fails, it will cause damage and injury. Don't remove a tree because the homeowner is the loudest or knows the mayor and says it Must be removed. Always remove the most dangerous trees posing an immediate risk to life and property first. Be consistent and transparent in the review process and communicate with all members of the community.

Develop a Clear Tree Risk Management Policy

Create a policy for the municipality and its tree program stating its goals, details for achieving those goals, and who will administer the policy. For example, the overall goal of a community tree risk management program is to reduce the risk for injury and damage to people and property through the proper selection, planting, and maintenance of trees within the rights of way and in park settings. The policy needs to clearly articulate who does what, what methods will be used, and what resources are available. Elected officials should agree to the policy and sign a resolution adopting it.

Two guiding principles of most successful programs are

1. to increase public safety by reducing risks associated with trees that have defects or visually obstruct traffic signs, intersections, or street lighting; and
2. manage the community tree resource to promote tree health and sustainability.

Both guiding principles can be achieved through the goals of

1. preventing hazardous tree defects through the implementation of proper arboricultural practices that promote tree health and structurally sound trees; and
2. correcting tree defects using a systematic process to detect and assess defects and implement corrective actions within a reasonable time.

Other goals could include hiring a municipal arborist, training the public works or park crews to identify defects, or coordinating with the public utilities to properly prune trees under electric lines and partnering on the removal of defective trees.

Urban Tree Risk Management: A Community Guide to Program Design and Implementation, published by the USDA Forest Service, can help guide a community in the development of a policy and a tree risk management program.

Hold Public Meetings to Discuss Tree Removals and the Inspection Process

Educating the community and individual property owners may help to resolve potential conflicts. Make sure tree defects are understood. When describing the tree's conditions, beware of using the terms "unhealthy" or "diseased." A diseased tree may not be a high risk, and a healthy-looking tree may have internal decay, root rot, or structural defects that could lead to failure of the tree.

When Needed, Utilize Municipal Code to Remove Dangerous Trees

Municipal code (state statutes) in Pennsylvania states the adjacent property owners are responsible for the cost of tree removals. Even if the municipality does not budget for tree removals (which it should), high risk trees should not be left standing along streets or in parks. Property owners should be notified that a tree should be removed. If the property owners do not remove the tree, municipal code allows the municipality to remove the tree and bill the property owner. If the property owner does not or cannot pay, a lien can be set against the property. This process should be a last resort. It is politically unpopular for elected officials if properties are being liened. Some municipalities have been very successful removing high risk trees through cost share programs with property owners.

It is near impossible to reduce tree risk in a community to zero without creating an environment that is devoid of trees and the benefits they provide to our communities. Developing a systematic approach to detecting and dealing with high-risk trees can, however, greatly reduce the risk of tree failures that cause injury and property damage. In the long run, this approach will pay dividends and save a municipality from a costly lawsuit. It might even save lives.