HK Afforestation

Hong Kong and Victoria Habour in 1820
Hong Kong and Victoria Habour nowadays
Human Impacts
 Temporal disturbance (e.g., noise)
 Direct attack to species (e.g., hunting,
 Disturbance to the ecosystem (e.g., pollution,
deforestation, hill fire)
 Destruction of the ecosystem (e.g., change of
land use, reclamation)
>>> degree, scale, rate?
Can we restore what we
 2 case studies
 Deforestation and plantation
 River and channelization
 Learn from the past, and cast light on the
Deforestation and Plantation
Hong Kong before 1840s
 Man has lived in this place for >5000 yrs. It is
believed that the destruction was very limited
at that time.
 Before 1500 A.D., the population was still very
spared. Then it increased very rapidly and it
reached 50000 by 1840s.
 City government planted Ficus microcarpa (细
叶榕) for the purposes of greening and city
“Bay and Island of Hong Kong” (1838) by Auguste Borget
细叶榕(Ficus microcarpa)
Hong Kong in the Imperial Age
 Systematic plantation started in 1870s, Pinus
massoniana (马尾松) was the only successful species
because of the infertile soils of HK.
 In 1880s, the government annually planted >100,000
siblings. Exotic species was introduced
experimentally from Australia:
Eucalyptus citriodora (柠檬桉)
Eucalyptus robusta (大叶桉)
Eucalyptus tereticornis (细叶桉)
Lophostemon confertus (红胶木)
 Deforestation had temporarily occurred when New
Territories was rent to British in 1898.
Hong Kong in the early 20th
 More exotic species were introduced. Among them,
台湾相思(Acacia confusa) and 银合欢(Leucaena
leucocephala) were two more successful species.
They can:
Survive in dry/harsh environment
Growing fast
Fix nitrogen
 Commercial forestry was an important commercial
sector. By 1930s, plantation extended from
lowlands up to the elevation of 250m.
WWII and Deforestation
 During the war time, large areas of woodland were
logged down due to:
The surge of refugee
Stop supply of firewood from China
 In 1953, the government launched a new forestry
policy and >100,000 siblings were planted annually.
More exotic species were introduced from other
countries. Pinus elliottii (爱氏松) was one of the
more successful species.
Tai Lam Chung in the 1950s
Tai Lam Chung nowadays
Plantation crew in the old days
The Birth of Environ. Forestry
in 60s
 Commercial forestry collapsed due to rapidly
declining demand for firewood after late
 In 1965, AFD stated that the objectives of
plantation were:
Soil conservation
Ecological conservation
Outdoor recreation
 AFD also sought the possibility of
establishing country parks in Hong Kong.
Country Park and Plantation in
 The enactment of the Country Park Ordinance in
1976 ultimately elimination the problem of illegal
logging. The key tasks left were hillfire prevention
and ecological restoration.
 In order to maximize the vegetation coverage in a
very short time, monoculture was common.
 The outbreaks of pests terminated the use of Pinus
massoniana (马尾松) and exotic species became the
main force of the plantation efforts.
Country Parks are the venues for plantation.
Exotic species
grow fast.
Plantation (1980s-now)
 Mixed culture and native (broad leaf) species
were included in the plantation program
because of aesthetical and ecological reasons.
 In the recent years, >500 thousand siblings
are planted annually. Among these, about
59% are native species.
Issue I: species selection
 The plantation recipe is simple. A small
number of species are generally included.
 The plantation program heavily relies on
exotic species. Among of them,
Lophostemon confertus (红胶木), Acacia
confusa (台湾相思) and Acacia
auriculiformis (耳果相思) are the most
important ones.
 The following lists the “Top Ten”
species. They represent about 40% of the
plantation efforts.
红胶木 (Lophostemon confertus)
台湾相思 (Acacia confusa)
耳果相思 (Acacia auriculiformis)
裂斗锥栗 (Castanopsis fissa)
毛叶桉 (Eucalyptus torelliana)
木麻黄 (Casuarina equisetifolia)
枫香 (Liquidambar formosana)
短花楠 (Machilus brevifolia)
爱氏松 (Pinus elliottii)
白千层 (Melaeuca quinquenervia)
The canopy of
exotic species
is spare
Issue II: restoration
 What does “restoration” refer to?
 Both exotic and native species have their
own strengths and limitations. How to
 How about fauna?
Exotic species: pros and cons
Harshness tolerable
Fast growing
available seeds
“Pest free”
May not naturalize
1. Not fit local
2. Shallow roots
The survival rate of native species is low. Even through it survives,
its growth may be stunted due to the harshness of the environment.
River and Channelization
Channelization History of Hong Kong
 ~1960 Under Public Works Department, Drainage Works
Office designed, constructed and maintained drainage and
 1964-67 Roads and Drainage Section formed, in charge of
Yuen Long Flood Control Scheme ( 元 朗 防 洪 計 劃 ) ,
successfully solve the local flooding problem.
 1967 Sewage and Drainage Advisory Group (later changed to
Drainage Works Division) formed, strategically investigated
the possibility of flooding prevention.
 1969-76 Shing Mun River Flood Control Scheme(城門河防
洪計劃), matched the development of Shatin New Town.
 Late 70’s to present
Channelization is considered as a
component of infrastructure.
 Late 80’s The issue of flooding re-appeared in NT
Channelization History (cont’d)
 1989
Drainage Works Division upgraded to Drainage
Works Department.
 1990 Issued Territorial Land Drainage & Flood Control
Strategy Study(全港排水及防洪戰略報告)。
 1994 Passed the land Drainage Ordinance.
 1995-2001 Main Drainage Works (MDW, 元朗區、錦田
 1995-2004 Shenzhen River Flood Control Scheme(深圳
 1997-2001 Rural Drainage Rehabilitation Scheme (RDRS,
Spatial Extent of Channizalization in HK
 No official data available
 From piecemeal data from annual reports
of Drainage Services Department and
formerly Public Works Department, it
seems likely that channelization is quite
extensively widespread in Hong Kong.
 Nevertheless, more channelization works
will be done in next 10 years.
Major channelization projects in Hong Kong
Environmental friendly design
 Channel
Unlined channel
Man-made point bar
Fish ladder?
 Riparian zone
Abandoned meander
Questions to ask
 Again, what does “restoration” refer to?
 The strengths and limitations of these designs?
 Rooms for improvement?
Restoration Plan
22 Feb 04
1 Apr 04
27 May 04
Hell (Before Restoration)?
Heaven (After Restoration)?
Further questions to ask
 Do you think the restoration is successful?
 What are the shortfalls?
 What are the necessary and sufficient
factors for success?
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