Most of the mangrove sites were considered high ecological value after field assessment as they supported moderate to high species diversity, and were subject to little or no human disturbance. The largest patch of mangrove surveyed was located at Pak Nai (Site 77) which comprised approximately 4.5 ha of land area. The mangrove at So Lo Pun was found to be densely vegetated with mangrove trees and supported high species diversity. Some mangrove patches, though small in size, eg Tai Ho Wan (Site 80), supported a comparable species diversity to those of larger sizes (eg So Lo Pun) and, therefore, a high ecological value was assigned.

Some habitats were found to have been disturbed by villagers, eg Pak Nai where some mangrove trees were cut to make a path to the mudflat located on the seaward side of the mangrove. The large mangrove patch at Tai O is also subject to disturbance from footpath reconstruction.

The mangrove at Tai Tam has been reported to have totally disappeared based on the field visit conducted in May 1996 (Tam and Wong 1997). However, the mangrove there (Site 82) was found during the field surveys for this Study to support a number of mangrove species, diverse epifauna, and was free from human disturbance. Despite its small size, the habitat is believed to be expanding as many tree mangrove seedlings, especially Excoecaria agallocha, were observed (see Table G7 of Annex G for details).

Some of the identified mangrove sites have had their ecological value downgraded to medium because of the severe disturbance from pollution or development that the habitats are subject to (Table 7.1i). The mangrove at Yuen Long, in particular, had been adversely affected by urban development and only a small patch was observed during the field visit.