March 2024

Urban Tree Risk Assessment- Perceptions, Reality, and Reliability. (Part 2)

Dr. Andrew Koeser

University of Florida


(To read Part 1, see our February 2024 issue.)


Lesson Two: We carry our biases and perceptions with us into our assessments

 

In another study, conducted again in collaboration with Tom Smiley and Bartlett Tree Experts, we analyzed the risk assessments and mitigation recommendations provided by nearly 300 arborists for a selection of trees. We found that the individual arborist evaluating the tree had the greatest influence on the assigned risk rating, even exceeding the impact of the tree itself. Furthermore, arborists with more credentials, particularly those related to tree risk assessment, and greater experience were less likely to recommend tree removal as a mitigation strategy. Interestingly, when controlling for other factors, arborists with children were more likely to suggest tree removal. These findings highlight the inherently subjective nature of tree risk assessment, which remains dependent on individual human judgment.

 

Lesson Three: The way we categorize tree defects currently is problematic

 

As I amassed storm data sets containing tree risk information, a peculiar pattern emerged. Several commonly monitored tree defects consistently failed to predict failures during storms. This observation prompted my team and me to conduct an international literature review, searching English, French, Chinese, Japanese, Portuguese, and Spanish databases, to identify additional studies examining pre-storm defect data. Unfortunately, we found few additional studies where defect data was collected and analyzed before a significant weather event.


Furthermore, studies comparing failure rates of non-defective and defective trees often revealed similar or even higher failure rates in the non-defective group. This unexpected finding prompted me to revisit my own data sets to replicate these results. However, the extensive list of defects currently evaluated by the industry renders encountering a "defect-free" tree highly unlikely.


This poses a significant challenge. Numerous studies have established that both defective and non-defective trees can survive storms, including low-intensity hurricanes. While pioneering research in the 1980s examined only a few defect categories, our current industry practice considers dozens, many of which remain uninvestigated and might solely reflect issues impacting timber suitability, not necessarily storm resilience. Instead of continuously expanding this growing list of potential risk factors for arborists to navigate, focused studies analyzing specific tree defects under actual storm conditions are crucial to identify which can be safely removed from the list.


See Part 3 in next month's TREE Press.

Lead Donors


We are deeply grateful to the following people and organizations whose accumulated contributions to TREE Fund in 2024 surpassed $2,500 or more as of February:


Altec/Styslinger Foundation, Inc.

John B. Ward & Co.

ISA Rocky Mountain Chapter

New York State Arborists, ISA Chapter, Inc.

Midwestern Chapter, ISA



See the full list of lead donors who make our vital tree research and education work possible on our website.

Welcome Suzette


Please join us in welcoming Suzette Guzman-Brown, who has joined TREE Fund as its Operations and Governance Coordinator. This newly created position will work regularly with TREE Fund’s various constituencies, working to ensure that routine operations and administrative functions are fulfilled in a timely fashion and will also work closely with the Board of Trustees in a de facto Board Secretary role, ensuring that the Trustees are able to focus fully on their crucial governance function with consistent and conscientious administrative support.


Suzette brings over a decade of experience in the non-profit sector, most recently with the American Cancer Society. She also brings extensive operations and executive level administrative experience to the organization and has spent time working at a nursery. She currently resides in California.


Ride With Us In New England! Tour des Trees 2024


We are well on our way to our goal of 100 riders at this year's Tour des Trees and we want you to join us too!


If you have always thought about taking part in our annual cycling adventure, this is the year to sign up! Join your fellow tree enthusiasts in New England, September 22 to 28, for five days of riding, education, comradery, and memories that will last a lifetime.


See our website for the latest information about where we'll be and what we'll be doing.


Registration and information can be found at www.treefund.org/tourdestrees.

Support Tree Research on Your Own Time


Can't make it out to New England but still want to support TREE Fund? Sign up for our Virtual Tour des Trees at home and complete your own Tour on your own time.


Ride, walk, run, or swim 425 miles by the end of August and fundraise to earn some cool, custom apparel, all while raising money for TREE Fund and tree research. Get your friends and co-workers together and schedule workout times throughout the summer so you don't have to do it all alone.


Details can be found at www.treefund.org/virtual-ride-option.

Be a Tour des Trees Sponsor and Show Your Support


As a nonprofit organization, we depend upon the generosity of our corporate sponsors and individual donors.


Tour des Trees sponsors have the ability to interact directly with riders and community members during the Tour and show that tree research is important to them.


If you or your company would like more information on becoming a TREE Fund or Tour des Trees sponsor, please contact Paul at pputman@treefund.org or Jonathan at jcain@treefund.org for more information or to see a sponsor kit. 

Free Webinars This Spring


Back again this spring, TREE Fund is proud to partner with the Alabama Cooperative Extension System to bring you free education offerings.


Next Webinar

May 2024. Date and time TBA.

Presenter: TBA

Presentation: TBA


Registration will be available two weeks prior to the webinar. See our Webinar page for more information. https://treefund.org/webinars


TREE Fund’s 1-hour webinars are free and offer 1.0 CEU credit for live broadcasts from the International Society of Arboriculture and the Society of American Foresters. Registration and information will become available on our website approximately two weeks before each webinar date.


Upcoming Webinars (registration opens about two weeks prior)

  • May 2024. TBA
  • November 2024. Dr. Greg Dahl. Tree Caused Outages – What we know and what we have learned.


Missed a webinar? Watch it anytime on our website.


CEU Credit for Recorded Webinar

TREE Fund offers ISA CEU credits for one recorded webinar: "Loading of a Tie-in Point While Climbing." If you missed this webinar, you can now watch the recording and earn ISA CEU credits by completing a 20 question quiz with 80% accuracy. Learn more on our website.

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TREE Fund is a 501(c)3 nonprofit whose mission is to support scientific discovery and dissemination of new knowledge in the fields of arboriculture and urban forestry.

TREE Fund recently earned our 2024 Candid Platinum Seal of Transparency! Check out our nonprofit profile to keep up to date with our impact. https://www.guidestar.org/profile/shared/17bf1c65-c913-4096-8695-11f0dc3fa73f.

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