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LCQ15: Proliferation of Mikania micrantha in rural areas and criteria in selecting plant species

     Following is a question by the Hon Cheung Hok-ming and a written reply by the Secretary for the Environment, Mr Edward Yau, at the Legislative Council meeting today (March 9):


     Mikania micrantha, Gairo Morning Glory, China dodder and water hyacinth are some of the invasive alien plants (IAPs) brought into Hong Kong.  These plants grow at an alarming speed, and if they grow into massive clusters, they will be hazardous to the native plants, reduce the biological diversity, and affect the ecosystem.  Recently, it has been reported that the proliferation of Mikania micrantha in rural areas is worsening, but the relevant government departments are not actively dealing with it.  In this connection, will the Government inform this Council:

(a) of the total number of sightings of the proliferation of Mikania micrantha reported to the authorities by members of the public, organisations or other government departments in the past three years; among these cases, the number of those which had been handled; and the number of locations with Mikania micrantha's proliferation found by the authorities during their routine inspections;

(b) whether the authorities have conducted any regular inspection of the locations where Mikania micrantha were removed, and whether they have identified any recurrence of Mikania micrantha's proliferation at such locations or in nearby areas; if they have, of the details; whether they have assessed if the current approach for eradicating Mikania micrantha is effective; and

(c) given that China is a state party to the Convention on Biological Diversity which was adopted in Nairobi on May 22, 1992, and this Convention also applies to Hong Kong, whether at present the authorities have formulated any relevant policy on prevention and clearing of IAPs; if they have, of the details; if not, whether they will study the formulation of appropriate measures; given that the authorities often plant trees, including non-native plants, in urban or rural areas, of the criteria they adopt in the course of selecting plant species for planting so as to assess if the species concerned are suitable for planting in Hong Kong?


(a) Over the past three years (from 2008 to 2010), the number of reports of Mikania micrantha received by the government departments below is as follows:

Department                        Number of
-----------                       ----------------
Agriculture, Fisheries
and Conservation Department(AFCD)     22
Lands Department                      32
Highways Department                    6
Water Supplies Department (WSD)        1
Leisure and Cultural
Services Department                    5

     The departments will conduct immediate site inspection after receiving complaints.  Weeding will be arranged once Mikania micrantha is identified.  If Mikania micrantha is found during routine inspections, weeding will be arranged by the venues' responsible departments.  For example, the WSD found Mikania micrantha on the slopes near two catchwaters in Yau Kom Tau and Tuen Mun, as well as the access between Tai Po Tau Raw Water Pumping Station and Tai Po Water Treatment Works.  It arranged for weeding immediately.  The other departments above do not keep statistics on Mikania micrantha found during routine inspections.

(b) The most effective way to prevent the infestation of Mikania micrantha is to conduct regular maintenance of plants.  Once Mikania micrantha is found, immediate weeding will be carried out to prevent its proliferation. According to the information provided by the above departments, re-emergence of Mikania micrantha after weeding happened occasionally.  The concerned departments will arrange weeding again as soon as practicable.

(c) The Government is committed to the conservation of Hong Kong's natural environment and biodiversity, and has been soliciting public support to protecting the local natural environment through education and publicity and other appropriate measures.  We are aware of invasive alien species that may adversely affect local ecosystems and have been monitoring the situation closely.  For example, AFCD monitors regularly the spreading of Mikania micrantha in Country Parks, Special Areas and Sites of Special Scientific Interest, and will arrange weeding once Mikania micrantha is found in order to protect local biodiversity.

     AFCD is responsible for tree planting in country parks. In selecting suitable tree species for planting, AFCD will consider the overall planting objectives, conditions of planting sites, characteristics of different tree species as well as their maintenance requirements.  For instance, if the planting objective is to control soil erosion, fast-growing species that are able to adapt to poor soil would be selected.  In general, native tree species are preferable as they perform better in adapting to local climate and enhancing biodiversity.  Currently, over 65% of seedlings planted by AFCD are native species.  To meet the planting objectives, suitable exotic species which do not endanger other plants will be planted if no native species are found suitable owing to special conditions (such as poor soil quality), landscape requirements for design concept or other factors.

     On planting in the urban area, the relevant departments adopt the principle of "the right tree for the right place" in the selection of tree species, having regard to factors such as the purpose of planting, the concepts of the landscape design, the conditions, space and climate of the sites, the characteristics and need for maintenance of different tree species, and the supply of trees.

Ends/Wednesday, March 9, 2011
Issued at HKT 12:10


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