SECTION 4 ECOLOGICAL RESOURCES CAPITAL STOCK
4.3 Impacts and Resource Constraints for Terrestrial and Marine Habitats and Species
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| 4.3.3 |
Marine Habitat and Species Loss |
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| 4.3.3.1 |
A number of different factors act to reduce the area of valuable marine habitat and in so doing decrease the species diversity found in Hong Kong's marine communities. In the marine environment these factors include coastal reclamation, dredging and disposal on the seabed, trawling and other destructive fishing techniques, navigational impacts, disturbance of beaches, and marine debris. |
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| 4.3.3.2 |
Figures showing the striking increase in coastal reclamations in recent years are given in Paragraphs 3.2.1.3 - 3.2.1.4 - Land Use and Land Supply. These activities have destroyed coastal areas that were previously used by marine organisms, particularly fishes, for spawning and nursery activities. This situation has been exacerbated by the replacement of these areas with smooth vertical seawalls at the seaward edge of the reclamations which provide little or no marine habitat value. Recently, however, greater attention has been paid to designing textured seawall to provide habitat value (although this must be balanced against the propensity of these structures to collect marine debris) and to off-site re-creation of habitats destroyed by reclamations (eg using artificial reefs). |
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| 4.3.3.3 |
As described earlier in this section (see Section 4.2.2.8 - Soft Bottom Seabed Habitats), a number of sites have been used for sand dredging activities in recent years. Similarly, the use of seabed areas as disposal grounds for contaminated and uncontaminated mud is discussed in Paragraph 3.5.3.7 - Solid Waste. At a minimum, these activities have caused a short-term disturbance to the seafloor environment through entrainment of seabed organisms, turbidity and/or sediment deposition impacts. More substantial impacts to coral communities have been documented at certain sites (Hodgson 1994). In some cases, for example when deep pits are left in the seabed, recolonisation of the natural seabed community may be inhibited. Studies have shown that disposed mounds of dredged materials are eventually recolonised but it remains unclear whether the pre-existing community will ever be replicated on disposal site mounds (ERM 1998d). Current policy states that exhausted marine borrow pits are to be used in preference to open seafloor sites for future disposal activities. This policy should reduce impacts associated both with the presence of deep sand dredging pits, and with seafloor mounds of dredged materials |
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| 4.3.3.4 |
Nearshore trawling activities exert a profound influence on the character of Hong Kong's soft seabed communities (see Paragraphs 4.2.2.6 - 4.2.2.8, Soft Bottom Seabed Habitats). Although Hong Kong's nearshore fish catches are not particularly valuable, fishermen are expected to continue to trawl intensively unless fishing efforts are regulated, the inshore fisheries resource is enhanced through artificial reefs, and/or the industry is converted to an offshore fishery (see Paragraphs 3.3.2.7 - 3.3.2.10 - Agriculture and Fisheries). Destructive fishing practices involving cyanide and dynamite, though illegal, may continue, particularly at the new artificial reefs sites, unless community or Government-led enforcement is effective. |
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| 4.3.3.5 |
Navigational activities may cause an impact to marine mammals in fairways or other heavily trafficked marine routes. The passage of high speed ferries through northwestern waters which provide critical habitat for the Chinese White Dolphin has previously been cited as a cause for concern. A recent study (Parsons and Jefferson 2000) has indicated that both dolphins and porpoises in Hong Kong have been found to have been killed by vessel collisions. However, this study only conclusively found 2 such cases over the 3 year survey period therefore whilst no major impacts have been reported to date, increased traffic on this or other routes could affect this threatened species. |
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| 4.3.3.6 |
Human disruption of nesting activities by the Green Sea Turtle (Chelonia mydis) at Sham Wan Bay has been reported in recent years. However, this area is now protected during the turtle nesting season as a Restricted Area. Enactment of this legal protection for turtle nesting activities illustrates that the appropriate regulatory mechanism was available in this instance, although enforcement efforts must be maintained for effective protection. |
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| 4.3.3.7 |
Disused floatable refuse, construction and demolition waste, and discarded fishing gear are all components of marine debris in Hong Kong. As with litter in the terrestrial environment, marine debris is not only an eyesore but can trap and disable or even drown marine organisms. Despite deployment of special floating refuse collection vessels in public areas, and anti-littering campaigns by Government, the volume of floatable debris remains high. Aside from publicised annual marine debris clean-up events in marine parks, public awareness of the issue is minimal. |
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