Cassian Humphreys underlines the importance of ethical reporting.
Using a recent arborist report of mine I am exploring the story behind the tree assessment. It was one that had me bat for the trees by putting responsibility onto the tree’s owner as opposed to those behind a possible council compliance breach. In this article I’ll also consider confusing council specifications and definitions.
Challenges
As with carrying out contractual works on woody plants, there are many challenges with assessing and reporting on trees. One of those challenges is picking your narrative. As consultants we owe it to ourselves and the tree for our bias to be neutral. This can be difficult. In some cases the bias is the client’s objective, in others it’s about the tree, and sometimes it’s about risk. The variables change every time, but the truth doesn’t.
Sometimes the client has a bias out of sync with the tree or the situation, and that makes the need for good observation and mediation by a consulting arborist paramount.
As with all tree work, we can rarely predict how a consultation will play out. It’s the consulting arboriculturist’s job to mediate between people and trees, and this is no less true of the tree contractor. The best jobs are always those that put the tree first, and often-times in doing that the client and stakeholders are well supported too.
That was certainly true of this project.
Summary
Following a request from a Brisbane tree company, I received a commission to report on a group of trees. Seeing the scope to make an article from it and wishing to share the subject with the greater community, here it is. As a means to deliver the message and to engage with the Australian arboricultrual community I’m writing this in the same format as I do with my professional reports.
The brief was to assess a small stand of boundary trees comprised of four live and one dead specimen, located on private land in a Brisbane suburb. The site was a multiple occupancy with a body corporate, and I was to deliver a status report on the trees following treelopping works and a possible breach in compliance. Under the Brisbane City Council’s Natural Assets Local Law 2003 (NALL), in the category of Waterway and Wetland Vegetation (WWV), the trees were subject to protection. My references involved a study of NALL documentation. I assessed the trees and supplied the report in November 2024.
The stand of trees are within the first third of their lifespans. For ease of reporting I address them as a stand, with reference to individual species where applicable.
To keep the report simple, concise and small, my discussion was necessarily included along with my observations.
Species, health, vitality, vigour and dimensions
Species: From left to right (numbers 1-5 in image 1) on site are Melaleuca spp – Black Tea Tree (1-2), Paperbark (3-4) and Corymbia torelliana – Cadaghi (5). The Black Tea tree on site is Melaleuca bracteata. The dead paperbark I could not identify, but it’s still-live neighbour Melaleuca nodosa is likely to be the same species.
Vitality: Bar the Black Tea trees (1-2), the paperbark trees’ (3-4) health or vitality is poor. T4 has died since the aerial image and council assessment was done. T5 shows signs of stress as a result of suspected excess saline water inundation from a neighbouring pool overflow. This is very likely to have killed T4.
Vigour: In this context vigour relates to genetic predisposition, both genera and all species have a moderate to strong genetic code, making the species resilient even when subject to poor vitality.
Dimensions (tree stand):
• Approximate tree stand height: 10m-16m
• Crown spread: 30m
• Diameter at breast height (DBH) of largest tree (T4) – 55cm
• Diameter above buttress (DAB) of largest tree – 60cm.
Tree/site observations
The trees are situated on the western boundary of the neighbour’s property. This is a sloping block, with the slope accelerating steeply toward the western side.
My primary observation regarding the site is excessive water run-off, particularly immediately adjacent to the swimming pool located behind the neighbour. I recognised a measure of saturation from rainfall, but one of the Paperbark Gums adjacent to the area of greatest saturation and the aboveground swimming pool is now dead. The Cadaghi Gum shows signs of stress due to the same boggy anaerobic soil conditions.
Roughly half of this tree’s root system is compromised. The water in this location and running down the slope into the client’s land is indicative of pool overflow.
Considering the health impacts on the stand of trees and an adjacent revegetation planting area, the anaerobic conditions in the soil, as well as toxicity from pool salts and chlorines, is a major concern. Health limitations and constant excess soil saturation is known to impact on tree root-ball stability as well.
Tree crown structure – treelopping, council VR definitions
No obvious historical signs of impaired crown structure were observed in the trees’ crowns, bar branch-fork inclusions typical to the Melaleuca genus. The tree-lopping works carried out by the tree contractor are possibly in breach of NALL and national/international standards for tree-pruning. As recorded by council’s aerial-mapping system, the contractor removed 50% of the trees’ volume. Sympathetic pruning carried out by a professional true to top-end international standards would have pruned less than an overall 2% to achieve crown/roof clearance.
Volume reduction (VR) as top-end works are in excess of the world’s pruning standards – of which the Australian standard falls short. However, in spite of the excessive overpruning or tree lopping for which the contractor is responsible, the impacts on the trees’ health are negligible compared to the impacts of soil water exudation caused by the overflow from the swimming pool.
Having assessed NALL documentation, I did, however, see a confusion around the definition of volume reductions. Whereas a VR as I define it relates to overall volume, this should not relate to crown height or spread. A 30% volume reduction is equivalent to a 5% height/ spread reduction over the whole of a tree. The volume is the collective amount removed by a 5% height reduction. To not specify this can only cause contractor confusion. In the compliance-notification-potential -breach NALL documentation it states ‘…in a given year 20% of a tree can be taken’. Removal of 20% of a tree’s crown from one side will place large diameter cuts into heartwood, as with Image 5. Removal of 20% over a whole tree’s crown spread is closer to a 2.5% crown height/spread reduction with small diameter cuts kept in the sapwood. The definitions in this documentation need to reflect this.
NB: Health stress is known to impact on the biomechanical status of trees, especially tree root-plate and root-ball mechanics when associated with water inundation.
Expected future tree-health impacts
I don’t expect any further tree-health impacts if the water overflow situation is fixed. Certainly not from the tree work. Tree lopping has impacts on photosynthetic capacity and is proven to lead to side effects as is covered in the global standards, but this is driven by plant vigour and plant vitality. Knowing the tree species involved, the tree works carried out as a one-off will have little to no impact. With reference to the health-impacts on the subject trees and the compliance notice, ref: Section 11, points ii and xi, by definition, state the residents of the neighbouring property are also potentially in breach of the tree-protection measures. Addressing this situation by plumbing the pool appropriately is essential to mitigate further tree-health impacts. 11. Pursuant to Schedule 4 of the local law, points A) and B) “interfere with” 1. (ii) to poison (including by contamination) 2. (xi) to effect any hydrological scheme which causes draining or flooding.
Conclusion
In conclusion, the stand of trees (T1-5) have recently been lopped, potentially in breach of the Australian Standard. The contractor in question possibly misled the property’s Body Corporate by stating that the works would involve targeting less than 20% of the trees’ canopies. Considering the sensitivity of relations between the neighbouring properties I am surprised council did not advise both parties to manage relations via the Queensland Civil Administrative Tribunal (QCAT). Though it is in the nature of the species of trees to outgrow the lopping works done, the trees are being impacted more by the pool overflow, which needs to be remedied for the long term. Had the parties gone through the QCAT process the right contractor capable of appropriate works would carried out the necessary pruning correctly.
The above was true to the original based on my brief report. All I omitted was client and neighbour references. The client’s bias was to avoid a fine based on non-compliance. The neighbour’s bias for notifying council, and having a potential breach imposed, was based on their position on the heavy lopping of two of their trees.
It will be interesting to learn what council decides.
