LCQ9: Tree management - Government World Magazine

Following is a question by the Hon Hui Chi-fung and a written reply by the Secretary for Development, Mr Michael Wong, in the Legislative Council today (June 27):

Question:

Last month, two 80-year-old Chinese banyan trees located at Bonham Road in front of Tang Chi Ngong Building of the University of Hong Kong were removed by workers sent by the Government for the reason that the trees had health and structural problems. It has been reported that some tree experts queried that (i) the risk assessment for the two trees conducted prior to the removal by an arborist of an outsourced service contractor was sloppy, and (ii) the Government had all along failed to maintain and manage the two trees in accordance with the standard for management of stonewall trees. In this connection, will the Government inform this Council:

(1) as the contractor engaged by the Lands Department was required to conduct regular inspection and maintenance of the two trees (including pruning) every six months since mid-2015, whether such maintenance work included (i) improving the soil at the trees' trunk bases, (ii) stabilising the structure of the low-rise wall which was wrapped around by the trees' roots, and (iii) taking measures to enhance the trees' immunity;

(2) given that the two trees met the definition of stonewall trees (i.e. most of the roots spreading on or penetrating through the wall face, and with the trunk bases situated within the confines of a wall), of the reasons why the Government had never maintained and managed the two trees in accordance with the standard for stonewall trees; and

(3) whether the Government conducted, in the past three years, any review on the system of outsourcing tree management, including reviewing whether the practice of awarding service contracts based solely on lowest bidding had led to poor quality of risk assessments for trees, thereby causing the Government to make wrong decisions on the need to remove trees?

Reply:

President,

Since 2015, the Government has closely monitored the conditions of the two banyan trees and the wall that they are attached to. Qualified arborists of the tree maintenance contractor of the Lands Department (LandsD) conducted risk assessments for the two banyan trees every six months. Upon receiving the assessment report every time, the LandsD reviewed the report in detail and verified the assessment on site. Resistance drilling test using tree inspection equipment on the trunk of one of the trees had also been conducted to determine the extent of rot inside the trunk. Similar resistance drilling test on the other tree was not possible due to site constraints.

Four officers in the Tree Unit of the LandsD are involved in reviewing and conducting on-site verification. All of them possess arboriculture qualifications, including Certified Arborists of the International Society of Arboriculture (ISA), Tree Risk Assessment Qualification of ISA, etc, and have more than 10 years of experience in tree risk assessment and maintenance. Amongst them, a senior tree management officer possesses a master's degree in arboriculture and urban forestry from the United Kingdom and has more than 20 years of experience in tree management.

Upon receiving the tree removal proposal from the LandsD in December last year, Certified Arborists with extensive experience in tree management from the Tree Management Office (TMO) also conducted site inspections and examined the conditions of the two banyan trees and the wall. Having comprehensively considered all factors, including stability of the trees and the wall, the health and structure of the trees, their location, usage of the nearby community facilities, public consequence of tree and wall failure, and availability of practicable mitigation measures, the TMO agreed that it was necessary to remove the trees before the wet season in the interest of public safety.

The TMO also invited tree experts from the Urban Forestry Advisory Panel (UFAP) to conduct field visits to stonewall and wall trees in Hong Kong on April 26, including the banyan trees at Bonham Road, and discussed the tree removal proposal with them. The UFAP members agreed that other mitigation measures were not feasible and tree removal was necessary, taking into account their threat to public safety.

The tree risk assessments for the two banyan trees were checked and verified by several ISA Certified Arborists and qualified arborists with extensive experience. The assessment was undertaken according to established procedures in a professional and rigorous manner.

My reply to the questions raised by the Hon Hui Chi-fung is as follows:

(1) Since mid-2015, the LandsD has arranged qualified arborists of the tree maintenance contractor to inspect and maintain the two banyan trees every six months, including pruning to reduce the weight of the canopy and removal of fungal infected parts. For other proposed maintenance works such as improving the quality of the soil around the basal area of the trees and enhancing the defence system of the trees, as the growth environment of the two banyan trees was undesirable, for instance, half of the root system was covered by footpath and road surfaces, and the other half was separated by the wall of Tang Chi Ngong Building, soil improvement would have a negligible effect in addressing the fundamental causes of tree deterioration. In addition, as the "self-repair" mechanism of the trees has failed and internal decay was observed in the old cut wounds of the two branches, the two trees showed irreversible health problems. Measures to strengthen the trees' defence system would have little effect.

Given that the footpath along Bonham Road is very narrow and the roots of the two banyan trees have already wrapped around the wall, reinforcing the structure of the walls is technically not feasible.

(2) The two banyan trees did not grow on stone retaining wall but have only wrapped around the adjacent wall. They are not considered as stonewall trees. This notwithstanding, the LandsD has closely monitored their health and structural stability since 2015, carrying out tree risk assessment every six months and implementing practicable measures to retain the trees, such as pruning to reduce the load and removing fungal fruiting bodies at the infected tree root .

(3) The Government reviews the system of outsourcing tree management works from time to time with a view to bringing in latest good practices. The LandsD's current tender evaluation process follows the established guidelines, which takes into account tenderers' past performance in previous public works projects as well as tender price. It is not based solely on lowest bidding. Furthermore, qualified tenderers must be listed in the Landscaping Category, Group II under the List of Approved Suppliers of Materials and Specialist Contractors for Public Works of the Development Bureau. In addition, all tree management departments must strictly comply with the Guidelines for Tree Risk Assessment and Management Arrangement to clearly stipulate the requirements for professional qualifications in arboriculture, training and related work experience in the contract. Only qualified personnel can be deployed to carry out relevant tasks in accordance with the requirements specified in the contract.

As mentioned above, the tree risk assessments for the two banyan trees were checked and verified by several ISA Certified Arborists and qualified arborists with extensive experience. The structure of the adjacent wall has been adversely affected by tree growth, showing deformations and multiple cracks. The wall has tilted towards Bonham Road, indicating high likelihood of collapse. In the event of heavy rain, the runoff may wash away the soil around the tree roots through the cracks on the wall, compromising base support and leading to tree and wall collapse. Tree failures are sudden, and it is not possible for passers-by and vehicles to escape in time. Therefore, when failing trees pose high risk to the public, removing them is necessary. The decision to remove the two trees at Bonham Road is justified and professional in the interest of public safety.