Homemade device may help arborists assess odds of falling trees causing damage

With a device they can make on their own for only $159, arborists can for the most part accurately assess whether people and pedestrians are at risk of danger if a tree falls in your yard. That’s way less than the machines on the market, which cost as much as $2,200.

More specifically, tree professionals can rate whether people or vehicles are in the fall zone of the tree, which can affect the outcome of a risk assessment and the subsequent mitigation.

That data-driven determination can save homeowners and businesses time and money because it can mean the difference between retaining a tree or its removal.

But how accurate is the DIY device? Ryan Klein wanted to test its precision. One way to find out is by calculating the target occupancy rate: a measurement of how frequently vehicles and pedestrians come close enough to get in the way of a falling tree.

Using a homemade device, as seen here, arborists can give homeowners and businesses a more data-driven assessment of whether a tree in their yard is likely to fall and harm vehicles or people, say UF/IFAS researchers.

Here’s a way to look at target occupancy rate: If an average of 100 people walk past a tree each day, and they spend an average of 4 seconds in the fall zone, then the target occupancy is 400 seconds (or 6 minutes 40 seconds) per day in the area where the tree might fall. That’s less than 0.5% of every day where a person might be within the fall zone if a tree were to fail.

For a new study, Klein tested the accuracy of the homemade device vs. the technology you can buy commercially. He found that you can quantify the target occupancy rate by using the low-cost traffic monitoring equipment.

“If the arborist that’s assessing the tree adheres to this type of calculation, you have a much better idea of the potential risk associated,” said Klein, a UF/IFAS assistant professor of environmental horticulture. “If a tree is likely to fail, the consequences are deemed to be unacceptable, and the occupancy rate is high, then the tree will likely need to be mitigated (i.e., pruned or removed) to bring the risk to an acceptable level.”

While the study’s findings are most useful to arborists, homeowners should be aware of defects in their trees and know how those defects might lead to the trees falling on property or people. Specifically, the more targets (i.e., people, vehicles, property), the higher the risk.

Until recent studies by Klein, arborists in the United States looked at trees and their surroundings and assessed the tree’s fall risk using subjective measures. The UF/IFAS tree researchers are trying to give arborists quantitative data so they can more accurately figure out if a tree might fall and cause damage or injury.

Although the homemade device generally works well, it gets less accurate when the temperature reaches 90 degrees or warmer. He and his UF/IFAS colleagues are working to hone the technology.

Klein offers this advice: “Be proactive with your tree care rather than reactive. Prior to planting,

select quality nursery stock free of major defects. When trees are young, prune them so they develop a strong structure that is free of major defects”

He conducted the new research with Andrew Koeser, an associate professor of environmental horticulture at the Gulf Coast Research and Education Center and Chris Dutton, a post-doctoral research associate in the UF biology department. Click here for more information about tree-risk assessments.


The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents.
ifas.ufl.edu  @UF_IFAS



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Posted: February 9, 2022

Category: UF/IFAS
Tags: Andrew Koeser, Arborists, Environmental Horticulture, Fall Zone, Falling Trees, Gulf Coast Research And Education Center, Homemade Device, Pedestrians, Ryan Klein, Target Occupancy Rate, Tree-risk Assessment, Trees, Vehicles

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