Documentation:Open Case Studies/FRST522/2023/Urban Forest Management in Hong Kong, China

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Summary of Case Study

The urban forest is all the woody plants and other vegetation in and near densely populated areas at different scales, from a small rural community to a metropolitan region. Managing this greenery can provide numerous benefits physiologically, sociologically, economically, and aesthetically to the urban areas and the community[1]. Hong Kong, known as a concrete jungle, only has less than a quarter of the land area developed. Together with high population density, this urban environment creates a compact city morphology, which can lead to thermal heat stress, particularly during the hot summer days, so the urban forest is important in acting as a buffer to offer a glimpse of the natural environment in this region[2]. With the increase in recognition of the positive outcomes that urban trees bring and the rising awareness of the potential tree risks to the public and properties, a range of strategies have been developed to encourage responsible urban forest management at both government and community levels. This article illustrates the current governance structures and methods employed in urban forest management in Hong Kong and discusses the potential challenges and recommendations of the urban forest sector.

Keywords

Hong Kong, Legal Framework, Stakeholder Involvement, Tree Risk Assessment, Urban Forest Management

Background

Geographic location, population, and climate

Hong Kong is a city in the southeastern part of China with a territory size of 1114.35 km2, consisting of the Kowloon Peninsula, Hong Kong Island, and New Territories, including Lantau Island and 261 outlying islands. The population is about 7.35 million, and the population density is 6,740 people per km2. Hong Kong has a sub-tropical climate characterized by hot and wet summers with intermittent rainstorms, as well as dry and mild winters. During the time from June to October, tropical cyclones are likely to occur, causing strong winds and heavy rainfall[3].

History and evolution

Before the British Occupation in 1841, grass and scrub were the most dominant vegetation in Hong Kong, and trees were only found on the remote hill slopes or around the established villages[4]. During the early colonial period, the administrative authority introduced an afforestation program to restore the degraded landscape. According to the historical records, the earliest street tree planting contract in Hong Kong was issued in 1847, and further tree planting works were conducted in 1861 – 1863 and 1868 – 1869. By 1883, over 3600 urban trees were planted, filling up all available spaces. As the street trees grew, they started to provide shade to the people during summer, and the streets then became a venue for social and recreational activities[5]. Later, lots of street trees were lost because of cutting down for fuelwood and construction[5][6]. As a result, a regulation was issued to prohibit illegal tree felling, and a Tree Preservation Ordinance was enacted by the Legislative Council in 1888 to protect the government trees[5].

The trees on Pedder Street in 1870

However, city expansion and further destruction during the Japanese Occupation (1940 – 1945) led to extensive city tree cutting. Years of planting efforts of previous afforestation programs were then undermined and negated within a couple of years. After the war, with urban building, although trees in localized areas were planted and preserved, the overall intention of replanting trees in other regions was low during the late 19th and early 20th centuries. In the 1970s, trees were planted gradually on government lands and private properties[6]. Before the handover of Hong Kong from the United Kingdom to the People's Republic of China (1997), the municipal services, Housing Department, and Highway Department were in charge of tree planting, while the Agriculture and Fisheries Department, Urban Services Department, and Lands Department shared the responsibilities of preserving and felling trees[6][7]. After the handover, the Urban Services Department was dismissed, and its functions on tree management were passed to the Leisure and Cultural Services Department and Food and Environmental Hygiene Department[7].

In 2008, a fatal accident was caused by a falling tree, and the Coroner's Court expressed concern about the public safety arising from the tree management programme. The government then improved the institutional framework and introduced a new management arrangement in 2010, which has been followed until now[8][9].

The benefits of urban forest

The development of urban forests in a city can bring multiple benefits to social health and the living environment, making the city more livable.

  • Air quality: Trees and vegetation can reduce the concentration of gaseous air pollutants, such as sulfur dioxide, and car-induced pollutants, such as nitrogen oxides and ozone, through uptake by the leaves to improve the air quality[10][11][12].
  • Cooling effect: Trees in urban areas can cool the temperature by releasing moisture into the air through evaporation and transpiration. Also, tree canopies can provide shading from direct sunlight, reducing the exposure to solar radiation of pedestrians[2][11].
  • Hydrology: Trees can contribute to hydrological processes in urban areas by intercepting the rainfall and enhancing the water accumulation capacity of soil via evapotranspiration to slow the rainwater runoff, which can diminish soil erosion and alleviate the burden on the drainage system[10][11][12][13].
  • Habitat for species: Urban forests can create habitats for a range of species, such as birds, bats, and squirrels, and thus enhance biodiversity, promoting a better ecological environment[11][13].
  • Promotion of physical and mental health: Urban greening spaces, such as urban parks, serve as a venue for physical and social activities, like walking and chatting, encouraging a healthier lifestyle and better interpersonal relationships[10][14].

Urban forest management in other places

Singapore

The idea of urban forest management in Singapore is to develop a “Biophilic City in a Garden”[15][16]. In 1975, the Parks and Trees Act was enacted to promote the preservation and conservation of vegetation in Singapore, creating a legal foundation for tree management[15]. The National Parks Board (NParks), established in 1990[16] and incorporated the functions of the Parks and Recreation Department (PRD) in 1996[15][16], is a leading authority on nature conservation and greenery management[16], managing 6 million trees including 2 million roadside trees[15]. In Singapore, a combination of top-down and bottom-up strategies is adopted. In a top-down approach, higher-level agencies, NParks, are involved in the decision-making and implementation of tree management practices[15]; while in a bottom-up approach, the Singaporean government encourages public engagement in tree management through the introduction of various programs to increase the connectivity of the people to nature[15][16].

Tokyo, Japan

With the aid of local communities and non-government organizations, the governments at multiple levels, the prefecture government, The Tokyo Metropolitan Government (TMG), and municipal governments share the responsibilities of urban tree management in Tokyo[17][18]. TMG and the municipal governments together develop measures to promote the sustainable management of urban greenery[18]. The Municipal governments manage 3500 ha of urban parks; while the Bureau of Construction under TMG manages 2000 ha[17]. The Bureau of Construction is also responsible for the maintenance of roadside trees following the Tokyo Metropolitan Street Tree Management Regulations established in 1954[18]. Another legislation, the Urban Green Space Conservation Act encourages public involvement in urban forest conservation plans to develop a livable urban condition[17].

Governance structures in urban forest management

The structure of the relationship between tree management departments

Trees on Government lands

Based on the suggestions by the Task Force on Tree Management in 2009, the Development Bureau (DEVB) formed the Greening, Landscape and Tree Management Section (GLTMS) in 2010, which adopted a holistic strategy for tree management, promoting proper maintenance and putting public safety in the first priority[8][9]. The Tree Management Office (TMO), one of the offices under the GLTMS, is a leading authority to implement the integrated approach for tree management effectively by coordinating with different departments. Under the framework of the integrated approach, the departments in charge of the maintenance of government facilities or lands under their purview are required to take care of the trees within their jurisdictions in accordance with the regulations and guidelines issued by DEVB[9].

In Hong Kong, there are over 1.6 million trees located on government lands and managed by nine core tree management departments[19]. These departments are required to conduct an annual risk assessment on urban trees situated in regions with high flows of pedestrians and traffic, and have to complete mitigation works before the rainy season in the Summer[9]. The number of trees managed by each department is shown below:

Table 1. Number of trees managed by nine core tree management departments[19]
Department Agriculture, Fisheries and Conservation Department Architectural Services Department Civil Engineering and Development Department Drainage Services Department Highways Department Housing Department Lands Department Leisure and Cultural Services Department Water Supplies Department Total
Number of trees 31,500* 145,600 8,900 14,600 585,000 88,000 N/A** 558,600 145,700 1,577,900

*The Agriculture, Fisheries and Conservation Department is responsible for managing all the trees in country parks, and this number only showed the trees located in frequently used regions and amenities[19];

**The Lands Department manages the trees on unallocated and unleased government lands. Because of the great number, tree counting is not conducted[19].

Trees on leased lands

All privately owned lands in Hong Kong are granted under government leases[20]. Leaseholders have the legal obligation to conduct tree management and ensure that their trees do not pose a threat to the public or property. Legal provisions clearly and objectively define the responsibility of land owners on tree management:

  • Common law: Landowners are required to manage their land, which includes the trees growing on it, under common law, to prevent them from posing a danger to the people. Failure to fulfill the duty can result in the owners being held accountable for the personal injury or property damage caused[21].
  • Building Management Ordinance (BMO) (Chapter 344): If property owners form an owners’ corporation (OC) under BMO, then OC will be responsible for the management of common areas in the building, including trees and other greening spaces[21].
  • Occupiers Liability Ordinance (Chapter 314): Property owners can be legally liable for violating the ordinance if injury or loss of life of a third party is caused by tree failure[21].
  • Provisions in Land Leases:  If the tree preservation clause is included in the lease agreement, approval from the Lands Department will be required for any significant tree trimming and tree removal works[21].

Urban tree management practices

Tree Risk Assessment and Management Arrangement

Trees are organisms that undergo transformations in their life cycle. Their health and stability, especially in urban areas, can be substantially influenced by external factors, such as weather, growing conditions, and human disturbance. Therefore, a long-term and effective management plan is essential to reduce the potential risks of tree failure. The Guidelines for Tree Risk Assessment and Management Arrangement (TRAM Guidelines) were announced by GLTMS, acting as a directive on tree risk assessment and maintenance in order to ensure public safety and promote sustainable tree management practices. TRAM is a risk-based dual approach composed of Area Basis and Tree Basis risk assessment[9][22].

Example of Category I Zone: Street with a high frequency of pedestrian and traffic flows

Area Basis risk assessment

The objectives of Area Basis risk assessment are to identify locations where the risk of tree failure would threaten public safety and disrupt human activities and allocate resources for tree risk management based on the usage frequency of the locations. Thereupon, a categorization of areas on the basis of the frequency of use and the associated risks is established, called ‘Tree Risk Management Zones’, which is divided into three groups: Intensive use with high risk (Category I), infrequent use with medium risk (Category II) and rare use with low risk (Category III)[22].

Tree Basis risk assessment

After defining the categories, Tree Basis risk assessment will then be applied only to the trees from Category I Zones, which have the top priority in management. Tree Basis risk assessment focuses on examining the tree's health and structure from a risk perspective using standardized forms, Form 1 (tree group inspection) and Form 2 (individual tree risk assessment), to record the findings[22].

Triage system

The triage system is a classification system exclusively for trees in the Category I Zone, with the aim of identifying trees that require special attention and thus prioritizing mitigation measures on these trees. Triage trees include dead trees, trees infected by Brown Root Rot (BRR), Old and Valuable Trees (OVTs), stonewall trees (SWTs), and large trees with a single trunk of DBH over mm or a height over 9m[22]. There are four classes:

  1. Black (Hazardous) – Trees categorized in this group are dead trees or non-OVTs infected by BRR, which need to be removed[22].
  2. Red (Attention) – Trees categorized in this group are OVTs, SWTs, or large trees infected by BRR or having significant structural defect(s) or health issues, which need further assessment and appropriate mitigation measures[22].
  3. Orange (Stressed) – Trees categorized in this group are large trees growing in a restricted area or on an unsteady foundation that may be susceptible to failure, which needs further assessment and appropriate mitigation measures[22].
  4. Yellow (Remaining Triage trees) – Trees in this group are those not classified in black, red, and orange classes, which need further assessment and appropriate mitigation measures, given sufficient resources[22].

Application of technology in management

Resistograph, Sonic tomograph, drones

Different tools are applied in management practices to further evaluate the tree conditions. For example, a resistograph is a resistance measurement instrument that detects the presence of wood decay or cavities and determines the extent of the defective areas by measuring the wood density. A sonic tomograph is used to assess the internal decay of a tree by recording the remaining wall thickness. A drone can be used to inspect and monitor the situation for a tree defect located at an unreachable height[22].

Tilt sensors

As the trees in urban areas are always subject to different environmental stresses, such as extreme weather and confined growing space, tilt sensors, an intelligent sensing device, were therefore introduced to detect the tree movement in Hong Kong and were installed on over 8,000 trees for long-term monitoring on tilt angle. This tool can help identify trees with potential failure risks in urban areas, thus enabling timely risk mitigations. The Hong Kong government announced a three-year project in 2021 to study further the effectiveness of the sensor in reducing the chance of tree failures and improving the department’s reaction to emergent cases[13][23].

Remote sensing multispectral imagery and LiDAR

Quick Response-coded tee label on a roadside tree

The GLTMS established a project in 2020 using remote sensing multispectral imagery and LiDAR regularly to monitor and evaluate the overall health and structural condition of OVTs and SWTs, and these practices can also help inspect the trees in an area that is hard to reach[9].

Quick Response-coded tree labels

By scanning the QR code on tree labels, the public can report problematic trees to the government more conveniently and access detailed information on the tree species for educational purposes. Currently, QR-coded labels are installed on about 200,000 trees in easily reachable places such as public parks, gardens, and roadsides[9][13].

Tree Management Common Platform (TMCP)

TMCP, launched in August 2020, is a digital governmental platform utilizing Cloud technology and Geographic Information System (GIS) for tree location identification, tree information examination, and spatial data analysis, promoting efficient management works[13].

Stakeholder involvement

Table 2. The stakeholder involvement in tree management
Stakeholders Responsibilities in tree management Status

(Affected/Interested)

Relative power
Government – Tree Management Office Coordinating authority among all tree management departments Interested: TMO is a leading agency to ensure the implementation of the tree management arrangement among departments. High importance;

High influence

Government - Tree management departments Agriculture, Fisheries and Conservation Department Managing trees located within country parks[24] Affected: Tree management departments are responsible for the maintenance of the trees assigned by the central government and are required to follow the TRAM guidelines to manage the urban trees. High importance; Medium influence
Architectural Services Department Managing trees on man-made slopes under the department's purview[24]
Civil Engineering and Development Department Managing trees located within governmental construction sites[24]
Drainage Services Department Managing trees located within drainage facilities[24]
Highways Department Managing trees on roadside artificial slopes/retaining walls and highway[24]
Housing Department Managing trees located within public housing estates[24]
Lands Department Managing trees on unallocated and unleased government lands that are not within other departments’ jurisdictions[24]
Leisure and Cultural Services Department (LCSD) Managing trees in LCSD sites (e.g., parks, sports grounds) and roadside landscape areas[24]
Water Supplies Department Managing trees located within waterworks facilities[24]
Outsourced contractors Managing trees assigned by the relevant departments Affected: Any changes in the criteria of the government projects can directly affect the qualifications of the contractors for bidding.

Interested: The success of the tree management contracts can be beneficial to the contractors in terms of monetary value and reputation.

High importance; Low influence
Educational institutions Providing arboricultural training or courses Interested: The courses provided by the institutions can promote the overall improvement of the industry. Medium importance;

Low influence

Private property landowners Managing trees on leased lands Affected: The duty of care on tree management by the private property owners is affected by the government policy or regulated by the relevant ordinances. Medium importance; Low influence
Public Engaging in tree management by reporting tree problems to the “1823” Call Center to facilitate the follow-up by responsible departments[24] Affected: The public is directly affected by the effectiveness of the tree management plan. Good management can provide benefits, such as a pleasant environment, while bad management can pose a risk to public safety. High importance;

Low influence

Challenges

Restricted growth environment

Roadside trees growing in a confined environment at Third Street, Sai Ying Pun

Hong Kong is a highly urbanized city, characterized by high-rise buildings and a high number of roads and streets, leaving only a small space for tree growth[25]. As a consequence, many urban trees in Hong Kong are growing in a confined environment, both aboveground and underground. For the aboveground part, the crown expansion of trees is usually obstructed by nearby multi-story buildings. Some common tree species, such as Aleurites moluccana, Acacia confusa, and Delonix regia, possess a relatively extensive crown spread when they turn mature[26]. Pruning, sometimes severe pruning, will then be conducted to ensure proper clearance between the tree and the property if their crowns conflict with the buildings, lamp posts, road signs, or power lines[26]. This practice can lead to a significant loss of the canopy, which affects the photosynthetic ability of the tree, and hence the health.

For the underground part, urban trees, especially street trees, are often found planted in a restricted area, such as a tree pit or a raised planter, causing a constrained belowground space for the development of root systems, which can adversely affect tree stability[27][28]. For example, the confined growing condition will limit the formation of buttress roots at the trunk base which is important in providing anchorage for the large trees to enhance the stability[28]. Moreover, some root defects, such as root rot and infection by fungal fruiting bodies, might become undetectable due to the coverage of the root system by concrete or pavement, posing potential risks to public safety.

Lowest bids win

In Hong Kong, many tree maintenance contracts in the government and the private market are awarded to the companies with the lowest bidding. This tendering arrangement can result in cutthroat competition between bidders because of extremely low pricing and affect the overall quality of the tree management practices as the awarded company might hire people with insufficient or lack of expertise or provide substandard services to cut costs, putting the public at risk.

Manpower shortage

Short on personnel is always a problem in the urban forestry sector in Hong Kong. According to the data in 2021, the number of trees on government lands was not in an appropriate proportion to the number of tree management personnel (Table 3)[19]. Except for the Agriculture, Fisheries and Conservation Department and Civil Engineering and Development Department, the number of trees managed per personnel was high among the other 7 departments, indicating an understaffed condition within the departments[19]. Two departments with the worst situation were the Architectural Services Department and Highways Department, which each person needed to manage 29,120 and 10,086 trees respectively[19]. The same phenomenon is also occurring in the private market. This might be due to a harsh working environment during summer, low wages and welfare, and recently, emigration. Together, this manpower shortage poses a challenge in ensuring proper tree care and maintenance in the city.

Table 3. Number of trees managed per capita in nine core tree management departments[19]
Department Agriculture, Fisheries and Conservation Department Architectural Services Department Civil Engineering and Development Department Drainage Services Department Highways Department Housing Department Lands Department Leisure and Cultural Services Department Water Supplies Department
Number of trees 31,500 145,600 8,900 14,600 585,000 88,000 N/A 558,600 145,700
No. of personnel 87 5 10 9 58 63 41 263 17
No. of trees managed per personnel 362 29,120 890 1,622 10,086 1,396 N/A 2,124 8,571

Recommendations

A better urban landscape design

To solve the problem of trees growing in restricted areas, the GLTMS advocates the principle of ‘Right tree in the right place’ for new planting in urban regions, which encourages proper tree species selection and planting practices[9]. For example, Ficus microcarpa which has an aggressive root system should not be planted in roadside tree pits because they might cause damage to the pavement when they are mature; while Xanthostemon chrysanthus is one of the commonly planted trees which has a relatively small mature size with a low-maintenance requirement[29]. Another suggestion for urban landscape design is the use of elevated sidewalks with integrated tree pits. The raised walkway not only allows for pedestrian movement but also provides space for root spreading and establishment. Moreover, permeable pavement can be used as the material for the raised sidewalk, which enables water filtration, and therefore alleviates water shortage and promotes nutrient uptake of tree roots[30].

Establishment of the legal framework

If any damages are caused due to the failure of trees on the crown or leased lands, people can seek monetary compensation from the government or the landowners through civil litigation. However, when a tree collapses due to human negligence, resulting in casualties, the people involved (tree inspectors or tree workers) may not need to bear any legal responsibility for the accident as no specific legislation has been instituted for urban forest management in Hong Kong. Therefore, there is a need to enact a legal framework to make sure the personnel can maintain their professional standards, and the establishment of disciplinary mechanisms also allows the investigation and addressing of professional misconduct. If anyone breaks the rules, a fine or imprisonment can be imposed.

Optimizing the tender system

To avoid vicious competition between companies, optimizing current tendering arrangements is important. At present, some of the tree management contracts are using a scoring system in which the bidding price is not the only factor considered during the selection process, other factors, such as past performance, can also contribute to the overall score[31]. Both the government and the private sector (like property management companies) should apply this system to all the tree maintenance contracts to prevent an extremely low bidding price and therefore have a better service quality provided by the outsourced contractors. Moreover, the highest and the lowest bids can be eliminated to avoid “cut-throat bidding”. As this is related to the public interest, a more transparent evaluation process is also critical.


This conservation resource was created by Course:FRST522.



References

  1. ↑ Konijnendijk, C. C. (2006). "Defining urban forestry – A comparative perspective of North America and Europe". Urban Forestry & Urban Greening. 4(3-4): 93–103.
  2. ↑ 2.0 2.1 Ng, E; Chen, L; Wang, Y; Yuen, C (2012). "A study on the cooling effects of greening in a high-density city: An experience from Hong Kong". Building and Environment. 47: 256–271.
  3. ↑ GovHK (2023, May 16). "Hong Kong – The Facts". Check date values in: |date= (help)
  4. ↑ Corlett, R. T. (1999). "Environmental forestry in Hong Kong: 1871–1997". Forest Ecology and Management. 116(1-3): 93–105.
  5. ↑ 5.0 5.1 5.2 Pryor, M. R. (2015). "Street tree planting in Hong Kong in the early colonial period (1842-98)". Journal of the Royal Asiatic Society Hong Kong Branch. 55: 33–56.
  6. ↑ 6.0 6.1 6.2 Jim, C.Y. (1987). "Land use and amenity trees in urban Hong Kong". Land Use Policy. 4(3): 281–293.
  7. ↑ 7.0 7.1 Lau, H.T. "香港樹木管理的思維缺陷" (PDF). The Hong Kong Institute of Landscape Architects.
  8. ↑ 8.0 8.1 Legislative Council Panel on Development (2009). "Report of the Task Force on tree management – People, trees, harmony" (PDF). Legislative Council of Hong Kong Special Administrative Region.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 Legislative Council Panel on Development (2023). "Review of roadside tree planting and maintenance" (PDF). Legislative Council of Hong Kong Special Administrative Region.
  10. ↑ 10.0 10.1 10.2 Dwyer, J. F.; McPherson, E. G.; Schroeder, H. W.; Rowntree, R. A. (1992). "Assessing the benefits and costs of the urban forest". Arboriculture and Urban Forestry. 18(5): 227–234.
  11. ↑ 11.0 11.1 11.2 11.3 Nowak, D. J.; Dwyer, J. F. (2007). "Understanding the benefits and costs of urban forest ecosystems". Urban and community forestry in the northeast (Second edition). Springer. pp. 25–46. ISBN 978-1-4020-4289-8.
  12. ↑ 12.0 12.1 Tyrväinen, L.; Pauleit, S.; Seeland, K.; Vries, S. D. (2005). "Benefits and uses of urban forests and trees". Urban forests and trees. Springer. pp. 81–114. ISBN 978-3-540-25126-2.
  13. ↑ 13.0 13.1 13.2 13.3 13.4 Legislative Council Panel on Development (2021). "Urban forestry management work in Hong Kong" (PDF). Legislative Council of Hong Kong Special Administrative Region.
  14. ↑ Lau, K. K.; Yung, C. C.; Tan, Z. (2021). "Usage and perception of urban green space of older adults in the high-density city of Hong Kong". Urban Forestry & Urban Greening. 64, 127251.
  15. ↑ 15.0 15.1 15.2 15.3 15.4 15.5 "The evolution of Singapore's legislative and policy frameworks relating to its natural landscapes". UBC wiki. 2019.
  16. ↑ 16.0 16.1 16.2 16.3 16.4 "Mission and History". National Parks. 2023.
  17. ↑ 17.0 17.1 17.2 "Urban Forestry Practices in Tokyo, Japan: Ecosystem Services and Challenges". UBC wiki. 2021.
  18. ↑ 18.0 18.1 18.2 "Tree management in Singapore and Tokyo". Legislative Council of Hong Kong Special Administrative Region. 2023.
  19. ↑ 19.0 19.1 19.2 19.3 19.4 19.5 19.6 19.7 "LCQ4: Tree management work [Press release]". Legislative Council of Hong Kong Special Administrative Region. 2022.
  20. ↑ "Land disposal and transaction: Waivers". Lands Department, HKSAR Government. 2021.
  21. ↑ 21.0 21.1 21.2 21.3 Greening, Landscape and Tree Management Section (2016). "Handbook on Tree Management" (PDF). Development Bureau. HKSAR Government, Hong Kong.
  22. ↑ 22.0 22.1 22.2 22.3 22.4 22.5 22.6 22.7 22.8 Greening, Landscape and Tree Management Section (2023). "Guidelines for tree risk assessment and management arrangement (10th edition)" (PDF). Development Bureau. HKSAR Government, Hong Kong.
  23. ↑ Abbas, S.; Kwok, C. Y.; Hui, K. K. W.; Hon, L.; Chin, D.; Ju, S.; Heo, J.; Wong, M. S. (2020). "Tree tilt monitoring in rural and urban landscapes of Hong Kong using smart sensing technology". Trees, Forests and People. 2: 100030.
  24. ↑ 24.0 24.1 24.2 24.3 24.4 24.5 24.6 24.7 24.8 24.9 Greening, Landscape and Tree Management Section (2023). "Purpose and Objectives". Development Bureau. HKSAR Government, Hong Kong.
  25. ↑ Jim, C. Y. (1987). "The status and prospects of urban trees in Hong Kong". Landscape and Urban Planning. 14: 1–20.
  26. ↑ 26.0 26.1 Jim, C. Y. (1997). "Roadside trees in urban Hong Kong: Part iv tree growth and environmental condition". Arboricultural Journal. 21(2) – via 89-106.
  27. ↑ Greening, Landscape and Tree Management Section (2023). "Common Tree Problems". Development Bureau. HKSAR Government, Hong Kong.
  28. ↑ 28.0 28.1 Day, S. D.; Wiseman, P. E.; Dickinson, S.; Harris, J. R. (2010). "Contemporary concepts of root system architecture of urban trees". Arboriculture and Urban Forestry. 36(4): 149–159.
  29. ↑ Greening, Landscape and Tree Management Section (2023). "Street tree selection guide" (PDF). Development Bureau. HKSAR Government, Hong Kong.
  30. ↑ Mullaney, J.; Lucke, T.; Trueman, S. J. (2015). "The effect of permeable pavements with an underlying base layer on the growth and nutrient status of urban trees". Urban Forestry & Urban Greening. 14(1): 19–29.
  31. ↑ "LCQ16: Enhancing tendering system for public works projects [Press release]". Legislative Council of Hong Kong Special Administrative Region. 2023.
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