SECTION 4 ECOLOGICAL RESOURCES CAPITAL STOCK
4.3 Impacts and Resource Constraints for Terrestrial and Marine Habitats and Species
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| 4.3.1.1 |
Given the importance of the ecological resources natural capital stock to sustaining the environmental quality of Hong Kong, it is important to identify factors which are expected to shape the future state of these resources. These factors, though manifold, are discussed in terms of loss of terrestrial habitat and species, loss of marine habitat and species, and environmental pollution. The following discussion will describe those strategies and policies that are already in place to counteract these threats and highlight those issues which are not being adequately addressed by current initiatives. An overview of these impacts is shown in Figure 4.4a (for terrestrial habitats and species) and Figure 4.4b (for marine habitats and species). |
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| 4.3.2 |
Loss of Terrestrial Habitat and Species |
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| 4.3.2.1 |
The most obvious form of damage to ecological resources is the direct loss of habitat and associated species through clearing or in-filling for large development projects or through catastrophic events such as hill fires. However, more insidious forms of habitat loss in Hong Kong include fragmentation, ie incremental damage to small patches of habitat, and erosional effects which damage the quality and stability of soils. In the face of such effects, many species which are not capable of adapting to alternative, remaining habitats are displaced and do not survive. |
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| 4.3.2.2 |
Many of the habitats that are most threatened by these impacts are those habitats which are most limited in area. Based on preliminary results from the HKU Biodiversity Survey and the SUSDEV 21 Habitat Mapping Baseline Survey (see Figure 4.3e), some of the habitats known to host the highest levels of biodiversity are those which are smallest in size. For example, high biodiversity areas such as fung shui woods, montane forests, and natural watercourses each cover less than 1% of the land area of Hong Kong, whereas grassland and developed areas (the "Other" category), which both support low or negligible levels of biodiversity, together cover over 40% of Hong Kong's area. Grassland and developed areas are both highly disturbed habitats and are expected to have lower species richness - such habitats are normally colonised by few smaller opportunistic taxa with faster growth rates that out-compete other larger organisms with slower growth rates. The relationship between small-sized habitats and high biodiversity may be explained by continual habitat destruction and encroachment acting to concentrate an increasing number of species in an area of decreasing size. |
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| 4.3.2.3 |
Other habitats are particularly vulnerable to development due to their low-lying topography and location near villages or in proximity to the coasts. These habitats, which include wetlands, mangroves, seagrass beds and fishponds, have been greatly reduced in area in recent years as discussed in Section 4.2 for each of the habitat types affected. |
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| 4.3.2.4 |
In the case of some habitats such as grassland, lowland forest, mixed shrubland and Baeckia shrubland, the SUSDEV 21 habitat map illustrates that these habitats are very fragmented in nature. An in-depth analysis of the extent to which fragmented habitat still fulfils its critical function would require detailed information on species' home ranges (ie to determine the minimum viable size of a habitat) and the necessary requirements for areas to act as "corridors" between critical habitat patches. As this information is not available for Hong Kong, it is not possible to explore whether habitat fragmentation is progressing toward or has already exceeded a critical threshold. |
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