Monday, April 7, 2008

ISA HK/China --- HK Tree News (Tree Climbing Accident in Yuen Long)

*** Our weekly Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas. Please note Station Mail is sometimes given in Blog at , although images are usually not attached due to size. ***

Dear Station Members,

Attached is an unnoticed local news on a Tree Climbing Accident happened on Apr 5, 2008 in Yuen Long. A young man of age 21 worried that the over-growth of a tree covering his house might break to damage the roof. He climbed & tried to cut off the offensive branches apparently without PPE & approved climbing equipment, & then fell to injure himself during the work. He was hospitalized at the end with broken legs.

Tree Climbing is dangerous !! Accident involving tree work has been ranking the top 5 industrial accident in North America for years. It has killed or injured more people than the police & firemen put together over there at one time. Anybody climbing a tree should be trained & properly equipped.

On the other hand, when we look at the current contract requirement for tree work in our territory, hardly any contract would require the tree worker to be trained for tree climbing for the work. So what would be the consequence if one does not climb, say, for pruning? If no climbing is performed, the worker would usually prune trees from bottoms up to remove the lower branches sequentially with a long Pole Saw. In time, the trees would grow taller in response to the lower branches being removed as compensation to regain foliage for Photosynthesis. Then the next pruning would remove more lower branches in the same manner. And the trees would grow even taller to produce more foliage on top. Hence the vicious cycle repeats.

Then can we do it with a bucket truck to reach within or above? It would be a safety violation if one tries to poke through the tree canopy with a bucket carrying a tree worker, because the fallen branches may hit the bucket, besides the boom of the crane can not manoeuvre safely within the branch structures. No licensed crane operator would like to risk that.

If anyone would study our urban trees after pruning for a few years, would the trees not usually be 'lion-tailed' with the lower branches removed mostly? Then how would 'lion-tailed' trees perform in the wind? With a higher Centre of Wind Pressure, they would break more easily in the same velocity of wind with a bigger Bending Moment. This may be why we have so many trees & branches failing after storms & typhoons, besides picking poor quality stocks & incorrect tree selection perhaps.

On the other hand, how can we require our tree workers to be trained for tree climbing, if our landscape supervisors can not climb themselves? This is a million dollar question indeed.

Singapore has begun to require their tree workers to learn tree climbing in their landscape contracts, even though Singapore does not have the typhoons that we know of. How should HK proceed? It also appeared that our CAP 509 Occupational Safety & Health Ordinance would require any worker to be properly trained for his/her duty of work, which may include tree climbing when tree work is to be performed. Are we breaking any laws as such without even knowing?

If anyone would still think tree climbing can be carried out without proper training & approved equipment, maybe he/she would like to consult this poor young man who just broke his legs in the news ...

best regards,

Sammy Au
Station Manager

The ISA Mission - Through research, technology, and education, promote the professional practice of arboriculture and foster a greater public awareness of the benefits of trees. (


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