Advisory Council on the Environment

Ecological Surveys and Database

(ACE Paper 13/2002)
For discussion


This paper briefs members on a territory-wide biodiversity survey programme and the establishment of an ecological database for Hong Kong.


2. Despite its small size and rapid development over the years, Hong Kong enjoys a rich biodiversity and is home to some 2,000 species of vascular plants, 200 species of butterflies, 100 species of dragonflies, 150 species of freshwater fish, 100 species of amphibians and reptiles, 450 species of birds and 50 species of mammals.

3. Urban development coupled with economic growth continuously put pressure on our natural heritage. Comprehensive ecological baseline information will facilitate the implementation of nature conservation measures. However, findings of ecological surveys undertaken thus far by academics and ecologists and those that form parts of previous environmental impact assessment (EIA) studies are not adequate to provide a comprehensive account of habitats of high conservation value in Hong Kong.

4. To address this problem, we will conduct regular biodiversity surveys to take inventory and update the status of our natural assets. These surveys will provide more comprehensive information that will facilitate our nature conservation work. Moreover, although these surveys are not intended to replace ecological assessment required of designated projects under the EIA Ordinance, which demands more detailed and focused examination of potential ecological impacts arising from projects, the information will help project proponents assess such impacts and take necessary precautionary actions at the early planning stage.

Survey coverage and objectives

5. On the basis of existing ecological information, we have drawn up a survey programme with a view to establishing a territory-wide ecological database for Hong Kong. The survey programme will cover all major habitats of high conservation value in Hong Kong. We plan to survey different habitats; the location, status and composition of about 100 plant communities; and the distribution and abundance of about 1,000 animal species. We will deploy trained personnel to all relevant parts of Hong Kong in the next three years to map out the distribution of different organisms using standardized methods and to collect specimens where appropriate for authentication and future reference. In order to ensure that the survey programme will be implemented effectively and a comprehensive ecological database will be set up, we will undertake comprehensive planning before starting the actual surveying work; ensure good coordination of tasks while the surveys are underway; and carry out meticulous analysis after the raw field data are collected. In addition, since ecology is dynamic, we intend to follow up the surveys with long term continuous monitoring and repeated surveys to update the database.

6. The items that we will cover in the survey programme are briefly described in the following paragraphs.

Habitat survey

7. A vegetation and habitat map showing the distribution and status of different habitat/land-cover types is useful to territory-wide land use and strategic development planning. It provides the basic information on the natural environment and essential information that will facilitate the development of effective conservation measures for protecting specific habitats and species. The information will also facilitate proponents of development projects in making an initial assessment of the potential ecological impacts arising from planned projects and help them avoid ecologically important sites at the early planning stage.

8. Under the Study on Sustainable Development for the 21st Century, an updated habitat map was prepared with 25 habitat/land-cover categories. As part of the on-going Study on Wetland Compensation, a habitat map covering all major wetland habitats in Hong Kong is also being prepared.

9. However, existing habitat/land-cover maps were produced mainly based on aerial photos and satellite imageries, with minimal field surveys to verify the habitat types and status. We will prepare a habitat map with all available information integrated into a centrally managed database and supported by field surveys and further analysis. The survey contents and methods for producing this map include:

  • interpretation of aerial photographs with adequate verifying field surveys;
  • assessment of the state of vegetation of the sites and classification of them into different natural habitats;
  • preparation of the vegetation and habitat map on a scale of 1:10,000;
  • regular updating of the vegetation and habitat map at an interval of not longer than once every 5 years; and
  • analysing the changes in vegetation type and naturalness of major habitats over time.

Plant survey

10. With its sub-tropical climate, Hong Kong has distinct wet and dry seasons. Together with the varieties in topography, it nourishes over 100 plant communities1. However, except for a few mangroves and sea grasses, we have no comprehensive information on the distribution and status of these plant communities.

11. We will map and monitor the distribution, status and composition of specific plant communities, in particular those which are natural and representative or typical of local habitats, irreplaceable or extremely vulnerable, rare or with high ecological values (e.g. in supporting rare animals), to facilitate the formulation of measures and conservation programmes to protect or restore them. This will involve conducting field surveys in each selected plant community, recording its boundary, plant species composition, and the level of disturbance and threat. The survey contents and methods involved include:

  • identification, categorisation and surveying of plant communities (e.g. sea grass, mangrove, fung shui woods, etc.);
  • drawing up of plant community maps at a scale of up to 1:1,000 for specific plant communities (e.g. mangrove, fung shui woods, Crapnell's Camellia); and
  • monitoring coverage and status of selected plant communities and updating of the plant community maps at 3 - 5 year interval.

12. We will also survey and monitor individual rare plants. Trees in the countryside that are unusual because of ecological or scenic reasons will also be covered in the survey. Rare plants and unusual tree individuals will be mapped. They will be assessed using the following criteria:

  • rareness;
  • size;
  • age; and
  • appearance & health condition.

13. A register recording the location, age, species, girth, and height of the plants and trees will be kept and maintained. Additional information on the ecology (e.g. vicinity situation, health, etc.) and protection status will also be recorded.

Animal distribution survey

14. We will survey and monitor the distribution and abundance of specific animal groups. The species groups selected are those which have widely been used as indicator species of the ecological value, level of disturbance and / or status of different habitats / sites. They include -

  • Mammals (about 50 species);
  • Birds (about 450 species);
  • Amphibians and Reptiles (about 100 species);
  • Freshwater fish (about 150 species);
  • Butterflies (about 200 species); and
  • Dragonflies (about 100 species).

15. However, it will not be possible to survey all the land area in Hong Kong for most animal groups meaningfully within a short time-frame. We will give priority to sites where rare species are expected or a high number of species are likely to be found (i.e. hotspots).

16. In the long-term, the survey will aim at revealing the distribution of the selected species groups at a resolution of up to one km (i.e. over 1,000 one km-square grids will be surveyed and the presence of target species together with their abundance will be recorded). This will be in line with the level of details adopted in previous studies (e.g. the Hong Kong Breeding Bird Survey and Winter Bird Atlas conducted by the Hong Kong Bird Watching Society), thus facilitating future analysis, particularly in drawing cross-reference and making comparisons with previous study results. The survey contents and methods for different animal groups are set out in paragraphs 17-26 below.


17. Auto-trigger cameras will be used for land mammals (except bats) in this survey. This equipment has been used successfully in mammal survey worldwide for studies on activity patterns, and spatial and temporal distribution patterns. It can record secretive animals, especially those that do not normally leave prominent signs. It also allows the collection of data day and night in a more standardized and consistent manner than most traditional methods.

18. Supplementary trapping using cage traps will also be carried out to collect specimens for biometric information (e.g. body size, weight, breeding status, etc.) and species identification.

19. In the case of bats, both trapping using mist nets will be used and counting of individuals in their roosts will be conducted. The number and species of individuals trapped / counted will be recorded.


20. The birds in Hong Kong can be broadly grouped as wetland or woodland birds.

21. The Hong Kong Bird Watching Society, under our subvention, has been coordinating the waterfowl and shorebird surveys in the Deep Bay area. This survey will continue and the data thus generated will be incorporated in the ecological database.

22. We are also liaising with the Hong Kong Bird Watching Society with a view to cooperating with them on the on-going survey of winter birds in Hong Kong. Their survey studies bird distribution on land at a resolution of one km. We plan to make use of their expertise in this well-established bird survey through subvention or direct hire of service so that the data generated can be incorporated into the database.

Amphibians and reptiles

23. We plan to conduct the surveys in-house with expert support, where necessary, from specialist organization(s). Major woodland and freshwater habitats will first be surveyed. The distribution and abundance of amphibians and reptiles will be recorded. Supplementary surveys will also be carried out in other amphibian and reptile habitats.

Freshwater fish

24. All major stream systems and freshwater habitats will be surveyed. Previous survey studies conducted by the University of Hong Kong have covered 28 freshwater habitats and 43 streams. For our survey programme, it is estimated that over 100 additional sites will need to be surveyed in order to produce a more systematic and comprehensive picture of the freshwater fish fauna in Hong Kong. Fish sampling will be undertaken using hand-nets and traps.


25. Surveys will be conducted through sighting and capture using hand nets to record distribution of butterflies. Where necessary, we will invite specialist organization(s) to participate in the surveys.


26. Due to a lack of sufficient number of naturalist groups interested in dragonflies, we will conduct dragonfly surveys in-house. Surveys will be conducted through sighting and capture using hand nets to record distribution of dragonflies in areas adjacent to major freshwater wetlands that are habitable to dragonflies

Involvement of specialist organizations and tertiary institutions

27. The survey programme will involve extensive and comprehensive surveys covering all the land area of Hong Kong. We plan to invite relevant local specialist organizations and tertiary institutions to participate in these surveys by providing specialist support/advice and/or to conduct specific surveys and studies.

Information compilation and management

28. Based on the survey findings, we will develop a systematic biodiversity database containing baseline information on Hong Kong's natural environment and biodiversity. We will update the database from time to time. Relevant information will be publicized and made available to the public, where appropriate, through the Internet and publications like books, posters and leaflets as part of our ongoing nature conservation publicity and education programmes.


29. We plan to start the surveys this year. All data will be compiled into the database once collected. It is expected that the comprehensive database will be available around 2005 when all the surveys, analyses and data compilation work are completed. Based on the experience gained in implementing the survey programme, we will review the survey methodologies and develop a strategy for continuously updating the database from 2005 onward.

Advice sought

30. Members are invited to note and comment on the survey programme as outlined in this paper.

Agriculture, Fisheries and Conservation Department
April 2002

ace_paper0213.gifHong Kong Vegetation. Supplement to the ACTA Scientiarum Naturalium Universitatis Sunyatseni 16, Vol 8. No. 2 (1989)




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