Forests and shrublands together constitute about 3737% (based on mapping of the habitat on the base map) of the total terrestrial area of Hong Kong and are the most extensive vegetation types found in Hong Kong. Forest habitats can be distinguished into fung shui forest, montane forest, lowland forest and plantation, which can usually be distinguished by geographic location and are generally of different species composition and hence biodiversity potential.

Fung shui forests are defined by their location behind current or abandoned villages and are often preserved because of traditional beliefs (Zhuang and Corlett 1997). These forest patches frequently host a diverse assemblage of plant species and are believed to contain remnants of the oldest surviving forests in Hong Kong. Fung shui forests are generally over 60 years old and dominated by native species. Younger or non-native fung shui forests typically have the same ecological value as other lowland forests. Although the overall area occupied by fung shui forest is only about 0.1% of the total terrestrial area (Table 4.2a), the habitat is comparatively species rich and known to contain rare plant species (Zhuang and Corlett 1997; Chu 1998). Currently, fung shui forest habitat is under-represented in Hong Kong's protected-area system and is threatened by urban development and village expansion (Chu 1998).

The majority of the fung shui forests surveyed for the SUSDEV 21 habitat mapping survey were small in size and subject to little or no human disturbance. Many showed a closed canopy and attained a canopy height of between 12 - 20 m. Protected and rare plant species, including Pavetta hongkongensis, Pygeum topengii and Xylosma longifolium, were recorded in some of the fung shui forest survey sites (eg North Lantau, Yim Tso Ha). The majority of the fung shui forests surveyed remain intact or only slightly disturbed by development, and were considered to have a high ecological value. However, there are areas (eg near Yuen Long Village) where disturbance to the habitat is great (with clearance of the under-storey for uses such as informal recreation) resulting in degradation of habitat quality.

Forest habitats other than those mapped as fung shui forests have been delineated into montane and lowland forest based on altitude, or classified as plantations when there is evidence of human afforestation (ie planting records and/or trees in recognisable rows). Natural forests occurring higher than 600m above sea level are classified as montane forest whereas forests below that altitude are regarded as lowland forest or plantation. Both montane and lowland forest types are the result of regeneration since the extensive cutting during World War II. While both forest types afford important habitat for a variety of flora and fauna, some patches of montane forest represent topographically protected areas which are most likely to contain species surviving since the early 19th century and are thus of particular importance.