In addition to the information collected from field surveys and the HKU Biodiversity Survey CD-ROM, existing information, which provides sufficient evidence for adjustment of the habitat value (ie upgrade or downgrade of the indicative ecological value), was also considered for individual habitat areas. However, the majority of the available information does not provide locations that are accurate enough to be identified on the habitat map (eg grid co-ordinates), though they are documented to be habitats of conservation interest (eg important habitats for protected/rare species). In addition, as some of the habitat types are highly variable and vulnerable to disturbance (eg wetlands), only up-to-date information on habitat quality will be used for value adjustment. Therefore, upgrading/downgrading of ecological value has only been considered if the data on the ecological status of a particular habitat are up to date and indicate a need for value adjustment when justified against the criteria set forth for ecological value, and for which accurate location is known.

It should also be noted that a conservative approach was adopted for ecological value adjustment of habitats based on existing information, ie a habitat will not be downgraded to a lower ecological ranking unless there is/are strong reason(s) provided by the literature to indicate that the ecological status of the habitat has been adversely affected (eg by pollution, development or other factors). The existing literature that has been reviewed by the Study Team for ecological value assessment and the action taken (ie upgrade/downgrade of ecological value) are provided in Table 7.3a.

The following sub-sections (7.3.1 - 7.3.4) describe the ecological value adjustment undertaken for the habitats concerned based on existing information.