My Portfolio

Welcome to my page, my name is Vik Cheung and I am Arborist in Hong Kong. I work for governmental projects to monitor trees located in both rural and urban area. Purview includes slopes, residential landscape areas, urban and country parks.

My page shares cases of tree risk assessment, common fungal infection, and uses of tree defect detection system, Sonic Tomograph & Resisitograph, the advanced detectable tools. Carried out 4 tree risk assessment cases are frequent encounter situation. They are including a failure old valuable tree in public park during a storm, Brown root rot disease infected tree, tree overcrowed in slope, and stonewall trees.

Review the current tree risk management in Hong Kong

It’s challengeable to maintain urban trees in Hong Kong. Heavy rain and storms are active from April to October. Conserve trees in good condition in such high population density city, effective risk control and precise assessment method must be needed. Each arboriculture workers handle 2, 900 trees on average. Hong Kong people are mass hylophobia of trees. They fear of trees special large old trees. It is because tree related people injury news reported occasionally. A woman was hit by a falling broken branch and died. Pregnant women fatally injured by a falling tree. Passing vehicles outside a housing estate were hit by a falling tree. Massive Hong Kong people think trees more dangerous than beneficial. How to improve tree risk management and public safety? How to live in harmony with our trees?

My tree risk assessment work is guided by “Guidelines for Tree Risk Management and Assessment”. It is issued by the Tree Management Office of Hong Kong Development Bureau in December 2012. It is formulated base on international best practices. It is a systematic way to assess tree risk and could provide information to tree owners and tree maintenance managers for making a decision to manage tree. That information helps to minimize a hazard occur from tree failure, and protect public safety, and maintain tree health.

The strategy of tree management is separated into 3 main categories:

Assessment
Mitigation
Monitor and maintain

The assessment is based on two aspects: area and tree. Firstly, carry out area analysis to identify the location where is constant use area with targets. Such as high flow of pedestrians walking path, parking area, busy traffic zone. Then, inspect trees group at those locations. Trees inspected will be categorized into three groups black, red and yellow, it is called TRIAGE system. It aims to prioritize the resources for handling risky trees first. Focus on those old and valuable trees, stonewall trees and problematic trees. They are needed to carry out individual tree assessment because they may have some structural problem, poor health or defects may harm the public or target. Examine the tree in detail including the structural stability of trees, find out harmful branches or parts, any fungal or pest infection and sometimes need advanced tools for investigating internal decay.

In order to prevent affecting our people and properties from the risk of tree failure. Appropriate mitigation measures will be adopted to remove the risk from the tree. For instance, pruning overgrown crown, remove broken branches and hangers, remove an unstable tree or dead tree, treatment for controlling pest and fungi.

Works should be done properly and in a professional manner. Monitoring measures are essential to ensure a good quality outcome. On-site supervise the frontline works, spot check site condition and tree inspection, an internal audit and counter check all the assessment reports by professional checkers and government tree management officials to approve the mitigation measure and tree removal application. Receive tree related complaints or inquiries from the public, it would help the government to monitor the trees nearby them and enhance the effectiveness of monitoring job.

Amelioration on tree risk management

In industry, there are some aspects should be ameliorated for better tree risk management:

Enhancement of assessment tools and knowledge: Technology should be upgraded. Professional training should be provided by the government. When we assess the trees, some area we still unknown and hard to find out and don’t know how to handle properly. Such as internal defects examination. Control pest and fungal disease, brown root rot trees care. The government should sponsor resources to scientists for inventing new instruments. Help to investigate internal defects in the rooting system, trunk more precise. Giving support to local universities establish systematic professional training to equip industry and to raise arborists’ knowledge connect with the international track. Provide tertiary education like Master, Doctor level of urban forestry, arboricultural and Mycology, Plant pathology, tree-related subjects. Refer to Case 4 Brown Root Rot disease(BRRD) infected Ficus altissima, there was no effective treatment for control BRRD. If we have advanced technology and better precautionary method, the no. of death caused by BRRD will be largely reduced.
To improve workers, arborists knowledge to tackle tree health problems and maintain adequate urban foresty. Increase the knowledge to plant species. How large area the tree needs? Can the tree withstand the wind load if plant it in a seaside park? This species will attract what natural creatures and will they affect the public nearby? This knowledge can help to make the right decision “plant right tree in the right space”.
Improve the mitigation method. Pruning, cabling, pesticides, fungicide treatment are commonly used to mitigate tree defects. To develop more effective methods to control fungal infection, inter departments should cooperate together to solve the tree problems. Such as remove pavement concrete to enlarge the rooting area for banyan trees. Realign the fence for increasing the spatial area for Ficus spp. growth their branches. Isolate the old and valuable tree with fencing to avoid pedestrians stepping on inducing compact soil and hurting the roots of the tree. Isolate and provide supportive staking to minor root plat movement trees to avoid people getting hurt from the tree falling and let the tree self-corrected and root growth for restabilization. Rather than just remove those trees. All parties should be cooperative to minimize the risk together. Make the tree risk to tolerance level and accepted by tree owners and the public.
Close monitoring and maintain trees properly. Regular tree inspection is essential to monitor the tree condition and identify the required maintenance measures. Increase patrol and audit trees in quantity and frequency. Tree inspection should be conducted by experienced workers with professional training. A timetable for tree inspections, 3 months, 6 months and 10 months by needs. A sensitive site or trees should be reinspected in short period. Such as Old valuable trees, stonewall trees, trees near a residential area and in busy traffic zone. Particular interest trees will induce public focus if removal. The government should consult with professionals and inspect the trees together. To discuss and design the most adequate and acceptable mitigation measures. The government should allow enough communication time and channels to collect public advice. Increase the transparency of tree risk assessment report to the public or concerned parties before action. To reduce conflict and emotional issues from them. Like Case 1 of Canarium album, this mature tree was failed during the storm Mangkhut. Citizens collect its fruits in the fruiting season for many years. Citizens love this tree. If remove this tree, will arouse public attention. We considered the public concern and used a bracing rod to limit the trunk movement and post a signage to alert people the situation of the tree.
Education to the public. People are threatened by biological lives, bird flu, dengue, bat droppings, rodents, education to the public is essential to conserve our natural resources and enhancing the bio-diversity. The public should understand a tree is getting old and dying. Failure is unavoidable. A tree has its life cycle. Trees can benefit us a lot. Shading, air filter, and aesthetic scene. How do we conserve them rather than just remove all unwanted trees? Talk and seminar to private tree owners, industry personnel and schools, tree-related activities to the public, such as nature walk, guided-tour in parks to promote tree science and the relationship with us. Storm precaution measures advertisement and promoting videos on social media like facebook, youtube, and TV. Invite the public to do surveys about trees, like counting tree species, record flowering and fruiting time, report problematic trees to tree management office in their living district. Make the people love trees and would like to protect them. Tree and people are in harmony.
Establish arborists registration and certification systems by academic knowledge and experience to raise the professional standards and their conducts. Let the public know who is a good or bad quality arborist. Set up an entry requirement for tree workers and inspectors. The government should lead the industry to meet with a professional level or qualification as the entry requirement. Restricted untrained personnel to carry out a tree risk assessment and routine maintenance work. All untrained or less experienced workers should be supervised by a well-trained in arboricultural profession supervisor when conducting tree assessments. It is a common mistake overlook tree defect which would cause delay removing the hazard-off the site. Improper pruning like topped trunks causes the tree lost energy reserve severely, induce health decline. Wrong application treatment of pesticides, fungicides, and even fertilizers will lead pollution to soil and water, also damage to the tree. More technical training, a protocol should be provided to industry. Qualified arborist and tree workers are insufficient. The government should employ and foster more professionals in this industry. Raise manpower to deal with urban forestry in good quality. This measure facilitates a better quality of tree preservation and removes the failure of the tree immediately. To reduce careless tree risk assessment and injury cases by falling trees or broken branches due to the delay of action.
Frontline tree inspectors are rush to inspect many trees a day to earn more money. Because their salaries are counted by how many trees they have inspected. More tree inspected earn more money. This is a disappointing result from the tender is awarded because of the lowest price. This malpractice in the industry cannot achieve a good quality of tree assessment and maintenance. Review the tender award procedure and consider the quality of contractor such as their experience, performance and conducts. Set up a reward and punishment system for encouraging contractor doing well.
Establish tree laws and regulations to mandate tree owners to carry out tree risk assessment by certified arborist regularly. Check their tree inventory and mitigation operation record. To ensure they maintain trees properly and reduce the risk from tree failure. Protection to arborist is also needed especially dealing with tree removal cases, an arborist is authorized to do their works legally. The government should issue a legislative standard for maintenance works, such as pruning, plant or relocation of trees, removal of trees. Tree management office can enforce the tree owner to prune the defective parts or remove the hazard trees by law.
A big tree in a small planter; overcrowded planting, fragile species planted in high wind load area; one species planting in an area which are common practice in Hong Kong. Refer to Case 2
Casuarina equisetifolia, when the tree getting old and became large, there was not sufficient area for its growth and anchor well. Severely restricted root caused the tree unstable. In long term, the tree could not recover. The leaning problem and imbalance position would induce tree collapse. The tree become an unacceptable risk. Tree removal is needed.
Recently, planting plan generally is designed by Landscape Architects. They intend to select exotic species, and not consider how big the tree is in the future, neglect local ecological issue. They mainly consider the aesthetic value and the client’s request. For the Case 3 Acacia confusa, the tree was planted in the insufficient planting area. The root system was restricted by drainage. During the planting design stage, designer was misdesigned or misestimated how large the tree would become. Finally, the tree suffered the pest and fungal infection. The tree was under stress, health declined and not able to self recover. If involving arborists’ advice during the design stage, it will be effective to avoid wrong selecting tree species in the wrong place. Tree failure cases can be minimized.

In the view of super typhoon Mangkhut in Sept 2018, storms damaged over 46,000 trees in Hong Kong. It was reported by South China Morning Post in Oct 2018. (Photo 1and 2, ). It’s time to take action to improve our tree risk management system and planting plan. Government advocates to plant more, actively promoting Greening Master Plan in all districts in recent years. A maxim ” Right tree in right place”, plant “more green” do not just consider how many trees we have to plant, should consider thoroughly on what we plant and how to preserve. Additionally, urge to raise the professional standard: precise assessment, correct mitigation measure prescribed, close monitoring and good maintenance work, transparent and communicate to publics, consummate management system and adequate tree legislative regulations are essential to do well tree risk management. Pursue to achieve zero injuries from falling trees.