urban tree management in hong kong problems and recommendations

8/4/2019 Urban Tree Management in Hong Kong Problems and Recommendations

1/21

Urban Tree Management in Hong Kong

Problems and Recommendations

Prepared by the Conservancy AssociationJune 2009

Introduction

As seen from the increasing number of media reports on urban trees

has been enormous public concern on the problems and accidents re

Among all these incidents, the breaking of a main branch of the Wishi

in early 2005; tree topping in Leung King Estate in 2006; the collaps

King Banyans trunk in Kowloon Park in August 2007; and the fatal ac

collapse of the Coral Tree in Stanley in 2008 received great comm

Conservancy Association (CA) strongly believes that they are resu

management of urban trees in Hong Kong and represent a genera

arboriculture among relevant government officials and landscape c

believe that the lack of overarching tree protection legislation has led

management of urban trees in Hong Kong. In this connection, we o

on the current problems of tree management in Hong Kong

comprehensive strategy in managing our urban tree resources.

Long term greening effect

5. Tree protection

4. Tree assessment and risk management


2/21

Urban trees are essential for any cities, particularly in congested c

Apart from providing a more pleasant environment and adding more

in area we live and work, urban trees can indeed help to ameliorateThe planting and maintenance of urban trees, especially in the dense

Kong, is a complex issue. There are several important and related

management which require careful consideration and attention in

comprehensive tree management strategy (See Figure 1). Failure in an

not only waste the resources and efforts being put in at earlier stage

in hazardous trees requiring more resources to deal with in the longe

those problems associated with these different stages in detail.

1. Planning and tree selectionOne of the most common problems affecting tree managemen

inadequate space for urban trees to grow. The tree survey condu

revealed that our city has failed to provide enough space to 87% o

studied (Figure 2). During rapid urban development in the past 20 t

by-and-large neglected the planning and care needed for trees to g

properly planted, when trees are getting bigger with time, they m

instead of assets of the society. It is one of the major reasons why th

tree failure cases in recent years.


3/21

(Shigo, 2003). If a wrong tree is planted in a wrong place, no matter w

and how many resources are being devoted to conserving such t

greening would still be poor. A well thought through decision in plantachieving long-term satisfactory greening effect in Hong Kong. A

highlight this point. Hong Kong Orchid Trees, (Bauhinia blakeana) ar

from 1999 to 2003. Over 70,000 individuals were planted in differe

Kong. However, the wood strength of Hong Kong Orchid Tree is weak,

individuals were damaged after several typhoon seasons and many o

removed or replaced. This is one of the examples that the selection o

resulted in increasing maintenance cost and at the same time

intended long-term and sustainable greening objectives (Figure 3).

Fig. 3 A Hong Kong Orchid Tree Garden was set up in Tung Chung in 2000. How

greening objective could not be achieved and the Government needs to keep

trees.

Strategic planting can help maximize community benefits wh

expenditures. The intention of the Greening Master Plan (GMP)

Unfortunately, the effort has mainly been put on planting mo


4/21

- Reserve enough space for tree planting: tree selection has to coof the planting, that is, whether the site can accommodate the s

to its mature size (i.e. diameter at ground level (DGL), height amature stage).

- If there is not enough space for planting trees, no tree shouldcould be planted instead.

- Tree species database: tree species database with detailed trshould be set up as a reference for all tree planting projects (Pleas

a suggested sample).

2. Tree plantingAfter selecting the right tree species, there is a need to have a good

ensure the long-term success of the greening effort. Tree stocks wit

structural defects shall not be used. Although guidelines and/or pa

are available for this purpose, on-site monitoring is often overlook

specifications are often not met (Figure 4).

Fig. 4 Planting a poor quality tree (such as this one with a twisted runk) will c

and extra maintenance cost in future.


5/21

(see Figure 5).

These kinds of unco-ordinated administrative arrangements shou

inter-departmental communication should be enhanced to prevent rproblems in the future.

Fig. 5 This tree was planted by LCSD correctly in the first stage. However, ad

after the installation of the pavement which led to the tree being buried too d

Recommendations:

-

Establish guidelines for tree suppliers for all government projedo not meet the standard, such as poor tree form, structural de

poor live crown ratio, should not be accepted by any governme

American Standard for Nursery Stock (ANSI A60.1, 2004) is a usefu

- Only trees that meet the said standard should be planted .- Prevent changes in soil conditions (including soil level) after tre

planting works should be carried out after all construction and paving) are completed. For example, pavement surrounding th

should be placed before tree planting in order to prevent tree da

change during pavement work.

- Pavement covered planting site: we suggest a minimum 1 m x 1


6/21

and reach maturity. There is no doubt that mature urban trees can co

input to our community in the sense of environmental, aesthetic, eco

and social aspects. Therefore, a proper and appropriate care to bottrees (Matheny and Clark, 2008) is one of the most significant fac

long-term greening objective.

One of the most common tree maintenance practices is pruning.

decay that may lead to severe damage to healthy trees. However, ac

of CAs tree survey (The Conservancy Association, 2006), 90% of the

been subject to poor pruning works (Figure 6). The result also indicat

in Hong Kong may not have enough knowledge and they are not supe

or properly by trained arborists on tree works. At present, th

requirement for qualified staffing carrying out such tree works.

Fig. 6a Topping in Leung King Estate in 2006. Topping is a

cheap way to prune a tree (around HK$500) but it will lead

to serious damage to the tree.

Fig. 6b Poor prun

result in serious d


7/21

through the course. Obviously, merely attending a course wit

examination and/or assignment projects would not equip workers

knowledge or know-how on practical tree works.

Recommendations:

- Raising the basic requirement for front line staff to carry out treetree management knowledge and skills of front line staff (bo

supervisors), the existing CICTA Supervision of Tree Work course

Examination should be required as a compulsory componenCertification. Recertification arrangement (collecting continuou

after every 3 to 5 years practice has to be imposed in the future t

in the arboricultural sector would continue to learn and update

know-how on tree management.

- Bringing up management professional for tree industry: highetree management is strongly recommended. Postgraduate c

courses, etc., should be set up for providing a proper professio

management for the industry in long term.

- Recognized qualification for tree management industry:qualification framework is suggested to be established in differen

tree works (from hands-on, assessment to management, etc).

arboriculture are divided into eight levels according to the N

Framework (Britt Chris, 2008). According to academic backgrou

can be classified from level 1 (certification holder) to level 8 (doc

In Hong Kong the existing Qualification Framework is a similar sys

for tree management industry. For example, workers carrying ou

should meet basic requirement, level 1, and tree assessment sho

people with at least level 2 qualification. This can help ensure th

management works in Hong Kong, as well as providing a path for c

4. Tree assessment and risk management


8/21

iii. Establishing secure resources for risk managementThe above have clearly indicated that a comprehensive plan with

necessary to reduce the risk of urban trees. The first and secondassessment and control (Points i. and ii.). However, the governme

commonly adopted guidelines for tree assessment and manage

procedures for tree risk assessment and management (Figure 7) ca

standardizing the procedure. In addition, all assessment records, incl

and photo records have to be kept for references, reviews, as we

removal should be considered if tree poses imminent danger and no be carried out to reduce the risk.

Referring to Point iii., allocating adequate resources on risk managem

For example, the 110-people tree management team of LCSD takes c

trees in Hong Kong. On average, each staff member has to look af

Without prioritizing works and providing additional resources (i.e. ma

equipments, etc.), it is impossible to carry out adequate assessm

management.

1. Visual Tree Assessment and

Site Inspection2a. If tree is in imminent

danger of failing, take

immediate action to protect

target (i.e. people and

properties)2. Identify significant tree defects and

conditions that could lead to failure

3. Determine treatments, if any, that w

reduce risk.

2b. Perform additional

inspection (i.e. aerial, root

collar, decay inspection)


9/21

Fig. 7 Flow chart of tree risk assessment procedures (Fig. 7 Flow chart of tree risk assessment procedures (Fig. 7 Flow chart of tree risk assessment procedures (Fig. 7 Flow chart of tree risk assessment procedures (Matheny an

4.2 Proper Training for people carrying out tree assessmentReferring back to the fatal accident in Stanley, it appears that tree as

1 and 2 (including 2a and 2b) as shown on Figure 7 were executed

results may be inadequate or incomprehensive to reveal the real

proper action. Professional training and close monitoring should be

that the quality of front-line staffs assessment work is up to standard

Recommendations:

- Reviewing previous tree failure records to prioritize trmanagement need: For example, according to major tree failure

June 2009, Candlenut Tree (Aleurites moluccana), Chinese Hackb

Flame Tree (Delonix regia) and Horsetail Tree (Casuarina equise

height are the major failed tree species (Appendix 2). Assessme

priority can be given to these trees first.

- Understanding the knowledge of existing tree assessors and suitable training: before providing training to front-line t

assessment knowledge test is suggested to be put in place.

Government to have a better understanding on the workers lev

facilitate planning for suitable training for them.

- Detailed tree assessment: Hazard Rating System (Matheny aBS8516, 2008) should be used to help to prioritize limited w

significant problems or hit targets. Matheny and Clark (1994) pro

of a detailed tree assessment items and form for tree ha

management (Appendix 3). Tree characteristics, site condition,

and hazard rating were included. Mattheck and Clark (2006)

reference figures for the threshold on tree failure due to internal d

Internal problem Threshold valuea


10/21

5.

Tree Protection5.1 Tree protection regulations

There are various Ordinances and Regulations related to tree protecti

Country Parks Ordinance; Forestry Regulation; and Crimes Ordinan

stringent Tree Preservation Clause governing development land un

leases after the 1970s for protecting trees in Hong Kong. However, n

protection is given to trees on private lands because the ordinances cover trees on Government lands. The Tree Preservation Clause is no

leases of private lands before 1970s. In other words, the site owner c

no liability or simply to cut the tree first before applying for the re

(Figures 8a and b).

We suggest a new tree protection ordinance like the Tree Preserva

UK and Australia, to conserve valuable and significant trees on private

It should protect the registered trees from unauthorized tree works

penalties. The Government should provide technical advices to

registered under the new ordinance. It is also important to educate th

tree ordinances, such as TPO does not stop the cutting of any tre

However, prior application and approval are needed before cutting d

land. This should prevent unnecessary cutting or removal of trees.


11/21

approaches. To ensure proper tree management in the long run, tree

in different stages (from planning and selection to tree protection) sh

people. As such, a tree ordinance is required for ensuring that onlycould carry out tree management works.

The following principles are recommended for the proposed tree ordi

i. Trees, especially mature trees and woodland in urban arare important asset and should be protected. Woodecological or environmental value should be designated

Area. Tree Conservation Areas should not be stamped

Trees with unique cultural and historical values should al

ii. Felling of a tree with Diameter at Breast Height (DBH) labe approved by the responsible Authority. Written

obtained before trees could be felled. Unauthorized trpenalized.

iii. The process of tree felling application should be tranlarger than a certain scale should be disclosed to the pub

be duly consulted.

iv. Planting trees in private lots should be encouraged. If thpublic, the developer or owner should be compensated.

v. Management and maintenance works of trees shoulqualified arborists. A professional body should be author

for maintaining the standards and handling complaints.

As trees are public asset, there should be adequate and genuine com

in tree protection and devising a greening policy.

Recommendations:

- Tree Preservation Order: we suggest a new tree protectionthe Tree Preservation Order (TPO) in UK and Australia to c


12/21

5.2Trees and development - Tree survey and transplantation

Tree survey should be carried out during the planning and early desig

is an in- depth inspection of the existing trees covering the details of

to be affected by the works. The main purpose of it is to facilit

application process at the later detail design or construction stage. H

surveys only record basic information and has been criticized for NOT

the structural integrity, value and suitability for transplantation of treis one of the key pieces of information deciding whether a tree should

currently not included in tree surveys (Figure 9). The consideration

life expectancy of different tree species will contribute to better

resource allocation for preservation and transplantation of trees. Fo

short lifespan such as Taiwan Acacia ( Acacia confusa) and Elepha

tanarius), transplanting mature individuals may result in dying with

time. We suggest that only trees in good health and structure, an

should be considered for transplantation (Figure 10).

In addition, it is observed that there is no special monitoring or

transplanted trees after the construction project is completed. Tree la

the transplanted trees which may eventually cause damages to

embedded or girdling in the tree (Figure 11).

When a tree is planned to be transplanted, the transplantation work

with the highest standard. Topping and small root ball are the most c

in transplantation of trees in Hong Kong because of convenience

result in poor survival rate and disfiguring of those valuable trees a

This has to be stopped. A review of the existing requirements in t

trees on our road systems is needed to facilitate transplantation of lar


13/21

Fig. 10a. Tree with significant structural defects

(V-crotch) and embedded metal bar was also

transplanted.

Fig. 10b. This strange tree

Tree being cut into pieces

Fig. 11 A single tree has 4 tree survey labels from different works in the past.

received no caring after construction works Those wires and nails on the tree


14/21

- Making transplantation successive rate available to public: stransplantation project should be made available for general p

monitoring.

5.3 Trees and development Excavation

Frequent utility and road works are constant threats to roadside

Excavation always damages the fine and supporting roots of trees, wh

and even stability of the tree. Trees may fall under strong winds if

were cut. To prevent the damages of roots of roadside trees duringbetter communication and closer monitoring by Government depar

for tree caring are absolutely important during construction works. O

to be carried out by tree specialists to prevent severe damages of tree

Recommendations:

- Pre-excavation protection and post-excavation caring have to bmaintenance department(s). This can minimize during work da

proactive caring work after excavation once needed.

- Providing a reasonable distance between excavation work and trIdeally, a 2.5 meter distance from the tree trunk is required for

(Mattheck and Breloer, 2006). For new development site, unde

trees should be separated with this distance as well to minimize f

utility maintenance.

6. Enhancing tree related research to achieve scientific managemenHong Kongs tree management work mainly confined at operationa

levels. Good and effective tree management has to be based on

However, such researches are lacking in Hong Kong.

To achieve scientific tree management, a good and comprehensive

starting point. Apart from basic tree information such as tree s


15/21

showed that a more systematic procedure should be set up for post t

When there are tree failure cases (regardless of whether there are

instead of removing the whole tree (including the root system) detailed investigation should be carried out to establish the major ca

data could be collected through these studies for predicting and ma

failure under similar conditions could be avoided. The data can help

susceptible species, age, or other environmental conditions for

information is very useful in work prioritization, especially wh

resources are limited.

Recommendations:

- Set up Urban Tree Inventory: to systematic manage all tree inforgeneral tree information, condition and caring history should be in

- Tree GIS data should also be available to other government demanagement companies. With different GIS data (i.e. tree l

location, communication line location, etc.) putting together, a

available during the planning stage of construction or maintena

Fig. 12a A fallen tree at Ho Man Tin. LCSD tired to

remove the whole tree within a day after the

failure. This would hinder the study of the

causes of the failure.

Fig. 12b The location of

Kong was covered by

ornamental plants within


16/21

7. Community EducationIt is important to have the publics support for tree management aInformation on Governments Greening

(http://www.devb-wb.gov.hk/greening/tc/index.htm ) can be further

more proper information on tree management, caring and conservati

For Registered Old and Valuable Trees (OVT), we suggest providin

stories, current conditions and management plans on t(http://ovt.lcsd.gov.hk/ovt/index.jsp ). This can help the general public

the importance of the OVTs, thus providing more support to the

conservation works.

Recommendations:

- Setting up special channel/ hotline for tree related enquiry: government to set up special hotline for helping the general

related problems. General information and support for tree ca

provided for trees even on private lands.

- List of recommended tree caring companies will be important fto follow up on private owned trees. Government can set up ev

and complaint systems for regular enhancement and review

performance.

- Public involvement in OVT management: we suggest secommunication channel for nomination, problem rep

enquiries/complaints regarding OVTs. With public participation,

not merely become more transparent, but also can gain mor

general public.

8. Coordination on Tree Management Works in Hong KongThere are 4 Bureaus and over 10 government departments taking c
http://www.devb-wb.gov.hk/greening/tc/index.htmhttp://ovt.lcsd.gov.hk/ovt/index.jsphttp://ovt.lcsd.gov.hk/ovt/index.jsphttp://www.devb-wb.gov.hk/greening/tc/index.htm


17/21

case in the future.

Furthermore, there is no monitoring on the tree works of d

departments. Monitoring has to be enhanced to ensure and improv

tree managing departments.

Recommendations:

- Tree Management Office: we suggest setting up a separate anManagement Office to enhance the communication, coordinatiotree works in the Government.

- Enhancing monitoring to Governments tree works: the Tree Mato be empowered to issue guidelines, monitoring and give reco

work and maintenance departments.

- Listen to tree experts: the Tree Management Office should aoversea tree experts to provide suggestions and comments.

- Listen to the community: community representatives, i.e. District invited to understand needs and problems related to trees from co

9. Literature Cited1. ANSI A300 Part 6, 2005, Tree, Shrub, and Other Woody

Standard Practices (Transplantation), Tree Care Industry Ass

2. ANSI A60.1, 2004, American Standard for Nursery Stock, ALandscape Association, 113pp.

3. Mattheck and Breloer, 2006, Body Language of Trees, Sta260pp.

4. BS8516, 2008, Recommendations for tree safety inspection5. Shigo, 2003, Modern Arboriculture, A.L., 440pp.6. Matheny and Clark, 2008, Municipal Specialist CertificInternational Society of Arboriculture, 279pp.

7. The Conservancy Association, 16th Dec 2007


18/21


19/21


20/21


21/21

urban tree management in hong kong problems and recommendations

Documents