Hong Kong International Urban Forestry Conference 2020 Acacia Management and Beyond Kathy Ng Chief Landscape Architect MLA MSc FHKILA RLA ISA CA ISA TRAQ HKIUD BEAM Pro 17 January 2020 This is an abridged version of the original presentation. Approval from Highways Department (and the original source of photos) have to be obtained for any form of copying, reprinting and reproducing. Landscape Division1 Highways Department Government Trees - Urban Areas (exclude Country Parks) around 1.7 million Highways ArchSD, WSD, 0.60 M Department DSD, HD & (35%) Others (HyD) LCSD Stonewall Trees Other departments HyD . Around 150 nos. Note: 1. Data as at March 2019 2. Source : Controlling Officer’s reply examination of estimates of expenditure, 2018-19, for Special Finance Committee 2 Highways Department over 10000 Expressways Slopes + HyD SIMAR slopes 11 km² (total open space in HK - 25 km2) 3 Urban Forestry cultivation and management of trees … physiological, sociological and economic well-being of urban society… (Jorgensen, 1970) …multi-managerial system… wildlife habitats, outdoor recreation opportunities, landscape design, recycling of municipal waste… (Society of American Foresters, 1974) …longer-term policies and plans for urban tree resources, and is connected to different sectors… …multidisciplinary …participatory (Konijnendijk et al, 2005) 4 Acacia Stonewall Trees Aging trees under stress Eucalyptus Background – Acacia 6 Background - Life cycle of Acacia confusa (台灣相思) 1950s 2010s Near future Acacia plantation scheme Senescent stage • life expectancy is about 50 years • soil erosion control/ vegetation cover • Health or structural condition of Acacia decline • slope stabilization faster at sites with poorer growing condition with shorter life expectancy • improvement of the fertility of soil The Ecology and Biodiversity of Hong Kong (Dudgeon, Corlett, 2004) 7 Senescent Acacia May 2018 Declined structural stability - heavy leaning and poor self-correction - poor stem taper and high height-to-diameter ratios - high susceptibility to wind thrown June 2018 8 Senescent Acacia Deteriorating health - high susceptibility to drought, soil compaction and secondary pathogens when injury occurs 9 Senescent Acacia Low ecological value - exotic species, not provide appropriate fruits for local wildlife - hinder the natural propagation and growth of native plants - reduction of light, moisture, nutrients and space - allelopathy - decline in one-go 10 Background – Acacia 1400 HyD’s Maintenance Record on Acacia Removal Note* Seven typhoons were recorded in 2013 (when compared with four to five in other years) The heaviest annual rainfall record was recorded in 2013 (among 2010 – 2015). 1200 1000 800 1282 600 892 400 808 863 824 721 200 443 284 341 0 2010 2011 2012 2013 2014 2015 2016 2017 2018 (Source: HyD) Year No. of Acacia trees 35% of all reported tree failure cases - Acacia (Tree Management Office, November 2012) 11 Objectives Public Safety Sustainability Biodiversity 12 Programme Workflow 13 1 Planning Ahead • academia • overseas + local tree experts • Tree Management Office • District Council + public 14 2 Prioritization of Risk and Work Apple Daily News 15 2 Prioritization of Risk and Work Acacia tree group survey form Prioritization Total score 3.樹木大小 (Tree size) (Higher priority) (>75分) 4.場地狀況 1.目標評估 (Site conditions) (Target rating) (Moderate priority) 5.場地紀錄 (50-75分) (Site sensitivity) 2.倒塌風險 (Failure potential) (Lower priority) Total score 100 (<50分) 16 3 Implementation GEO Technical Guidelines on Landscape Treatment for Slopes 17 3 Implementation Native trees Tsing Nam Road, Tsing Yi Mallotus paniculatus Sterculia lanceolata Litsea glutinosa Microcos nervosa (白楸) (假蘋婆) (潺槁樹) (布渣葉) Native shrubs and ground covers Psychotria asiatica Diospyros vaccinioides Psychotria serpens Litsea rotundifolia Ilex asprella (山大刀) (小果柿) (蔓九節 ) (豺皮樟) (梅葉冬青) 18 3 Implementation Biodiversity Enhancement Native Planting Schedule (Sample) Spacing Chinese Name Botanical Name (mm) Trees 餘甘子 Phyllanthus emblica 5000 潤楠 Machilus spp. 5000 豆梨 Pyrus calleryana 5000 桑樹 Morus alba 5000 小果鐵冬青 Ilex rotunda var. microcarpa 5000 假蘋婆 Sterculia lanceolata 5000 大頭茶 Gordonia axillaris 3500 Shrubs 梅葉冬青 Ilex asprella 500 車輪梅 Rhaphiolepis indica 300 崗菍 Rhodomytus tomentosa 300 野牡丹 Melastoma malabathricum 300 九節 (山大刀) Psychotria asiatica 300 朱砂根 Ardisia crenata 300 梔子 (白蟾) Gardenia jasminoides 300 Ground cover 腎蕨 Nephrolepis auriculata 200 Climber 薜荔 Ficus pumila - Note* Trees in small size (e.g. whips/ light standard trees) will be used to minimize the root pruning and cost for planting on site 19 3 Implementation – Pilot Scheme Wong Tai Sin Pui Man Street 20 3 Implementation – Pilot Scheme Shatin Yuen Chau Kok 21 4 Reuse • Upcycling 22 4 Reuse • Upcycling 23 5 Monitoring, Evaluation and Enhancement 24 5 Monitoring, Evaluation and Enhancement 中環蛺蝶 美鳳蝶 蛇目褐蜆蝶 報喜斑粉蝶 珍貴嫵灰蝶 古樓娜灰蝶 Neptis hylas Papilio memnon Abisara echerius Delias pasithoe Udara dilecta Nacaduba kurava . 斑鳳蝶幼蟲 白弄蝶 鈕灰蝶 銀線灰蝶 檀方粉蝶 黑邊裙弄蝶 Larva of Chilasa clytia Abraximorpha davidii Acytolepis puspa Spindasis lohita Dercas verhuelli Tagiades menaka 戈芬氏鳳頭鸚鵡 白腰文鳥 珠頸斑鳩 紅耳鵯 Cacatua goffiniana Lonchura striata Spilopelia chinensis Pycnonotus jocosus 25 5 Monitoring, Evaluation and Enhancement 26 5 Research Environmental Performance Evaluation and Pathological Assessment of Acacia Slopes Objectives • management measures to reduce Acacia failure • long-term maintenance plan • strategic replacement planting design • suitable replacement planting matrix for sustainable management 27 5 Research Pathological Assessment • Develop sets of parameters for evaluating Acacia slopes → Determine the needs and priorities for removal of Acacia trees Soil Properties Assessment • Collect soil samples → Analysis and compare data collected from pre-replacement period to post-replacement period Bird, insect and spider Survey • Conduct surveys on species, biological community found on site → Determine the effects of replanting on biodiversity at study sites Microclimate and air quality Assessment • Carbon uptake • Transpirative cooling • Air pollutant update • Air pollutant formation → Estimate air quality and climatic effects before and after replanting 28 6 Community Outreach 29 30 Community Bonding 31 Community Bonding 32 Community Bonding Saw mill Wood dryer Correctional Services Department Wood workshop 33 Community Bonding 34 Community Bonding 35 Ecological Corridor Enhancement 36 Slopes as the ecological corridor - re-connect community + habitats Existing greenery HyD Registered Slopes Node of connection Mapping of greenery area and HyD SIMAR slopes in Tseung Kwan O Seasonal distribution, size and type of fruits Examples of bird species in Tseung Kwan O District (Source: Hong Kong Wildtracks, HKBU library) Wildlife habitats + major flows of pedestrians and cyclists Blow-up Scenario 1 - Tunnel junction Blow-up Scenario 2 – Along cycling and pedestrian path Site photos of existing situation Managing large tree quantity + aging trees over 80% tree over 5m Proactive Urban Forestry Management - new technology –satellite/aerial photos, VIS, MMS, UAV, LiDAR • inspection • data collection • analysis • proactive measures • feedback + monitoring UAV inspection of Eucalyptus Tuen Mun Road 41 Tree Tagging Service Tree Attribute Survey Tree Location Survey Tree Database 42 43 Trial Application January 2017 March 2018 Tree Health Tracking 44 Ultimate Goal HYPERSPECTRAL SIGNATURE LiDAR MULTISPECTRAL IMAGES HEALTH AI DETECTION EARLY WARNING SYSTEM 45 Vision Thank you 46.