City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: http://read.dmtmag.com/i/599208
26 City Trees 26 City Trees Municipal arborists deal with many challenges managing trees on municipal and private lands. Among the most contentious items are requests for tree removal, dealing with poor or improper pruning, debates about where new trees might be planted, and endless questions about the costs, affordability, and benefits of trees in urban areas. The arguments presented need to be understood and validated before they can be accepted. This is done by reviewing the evidence, the assumptions underlying it, and the "facts" that supposedly result if the line of argument is believed. Often, the review will show flaws in the evidence, and the way it has been used to derive "facts." Evidence has several definitions, but in essence it is "proof supporting an argument, the available facts showing a proposition is true, or the information that supports a conclusion or opinion." Two fundamental principles always apply when col- lecting, analysing, presenting, or reviewing evidence: Know what to look for. Know what you are looking at. When reviewing reports or conducting site visits, clear- ly understand the assignment and be sure you know what to look for. If it is a tree retention scheme, then where are the building footprints, the service corridors, access roads, and of course, the trees? Have the trees been correctly located on plans? Are the symbols to scale and do they accurately reflect reality? Have the tree and site conditions been correctly identified or are some factors deliberately overstated in order to satisfy client desires to have the trees removed? Errors at this stage can create opinions or conclusions that are not defensible. In the reports or on site do you know what you are looking at? Do the development proposals reasonably reflect the extent of the actual or anticipated distur- bance? Do the drawings show these properly? Have the arborist and design professionals (engineers, archi- tects, landscape architects, planners) properly under- stood all of the implications? Again, errors at this stage can create false statements later on. An obvious example is risk assessment. The person wanting a tree removed will claim unacceptable levels of risk or disturbance as justification, and submit a report claiming to prove it. The information present- ed may be valid, but how can you be sure? Ideally, the report includes definitive statements about what was done, when, by whom, what they found, how they analysed it, and why they reached their conclusion. However, it is not unusual to find flawed reports, where the claims made are spurious, not clearly supported by credible evidence, or are simply wrong. Reviewing risk assessment or other reports should start with a series of questions. 1. Is the arborist actually qualified for the assignment and is their credential current? The Standard of Care in North America is the Tree Risk Assessment Qualification (TRAQ) promulgated by the International Society of Arboriculture (ISA) or similar tree risk assessment programmes promoted by federal or state government. 2. If the report deals with risk, what level of risk assessment did they undertake? The Best Management Practices - Tree Risk Assessment, published by the ISA, establishes three levels. The level used should be specified. 3. When and how did they undertake the work? What supporting materials were used? Site surveys, engineering plans? These should be referenced. 4. What did they actually see on site? Did they describe and illustrate it enough so that the reader can clear- ly see the issues described? Copies of plans, photographs, and other graphics should be in the report so that the reader can clear- ly see and understand the issues described. 5. Is the analysis credible based on what is claimed to be on site? 6. Is the final opinion believable? Does it seem rea- sonable in light of the evidence submitted, or is it simply written to support the answer that the client wanted, regardless of what was actually on site? Of course a similar standard also needs to apply to reports and assessments conducted by staff within a municipal organisation. Leading by example is an important way to promote better standards. When reviewing reports, it is not unusual to see bland or misleading statements. One recent example stands out. The writer claimed, "We conducted drill tests throughout the tree and all the results met accepted ISA standards." At first glance the statement sounds Municipal Arboriculture: Does the Evidence Support the Claim? by Dr. Julian Dunster (jd@dunster.ca), Dunster and Associates Environmental Consultants Ltd., Victoria, BC, Canada