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Area of individual survey habitats was rectified based on the mapping results obtained from field verification. A total of 111,711.8 ha was mapped for the terrestrial area (covers all land area above low tide mark) of Hong Kong (Table 9.2a). Among the 25 habitat categories mapped on the habitat map, grassland is the most extensive habitat which occupied 26,081.3 ha and constituted the highest percentage land cover (23.4%). The three forest habitats, ie Fung Shui Forest, Montane Forest and Lowland Forest, varied widely in their land cover: 16.3% of the total mapped area were identified for Lowland Forest whilst only 0.10% and 0.05% were mapped for Fung Shui Forest and Montane Forest, respectively. The total area mapped for Mixed Shrubland was 16,477.7 ha and comprised a percentage cover of 14.8% which is comparable to that of lowland forest. The remaining two natural vegetation habitats, ie Shrubby Grassland and Baeckia Shurbland, are much less extensive than mixed shrubland and constituted, respectively, 7.8% and 5.4% of the total terrestrial area. About 180 ha of land area was identified for plantation and comprised 0.16% of the total mapped area.
The land areas identified for the natural water (ie Natural Watercourse and Freshwater/Brackish Wetland) and intertidal (ie Mangrove, Intertidal Mudflat, Sandy Shore and Seagrass Bed) habitats are, in general, small and individual habitats occupied < 1.5% of the total land area. Seagrass beds showed a very limited distribution and occupied 0.04% (ie 41.1 ha) of the total land cover. Artificial or modified water habitats showed a comparatively higher land cover than the natural ones. Fishpond/Gei Wai habitat occupied a map area of 1,835.7 ha which is 1.6% of the total land area. A total of 2,827.0 ha (ie 2.5%) was mapped for Modified Watercourse.
Cultivation occupied 4,381.0 ha which constituted 3.9% of the total land area. The low value disturbed habitats, such as Golf Course/Urban Park and Quarry, showed a low percentage of coverage < 1.0%. Urban or highly modified area (including buildings), ie Other, was found to be extensive and occupied 16.9% (ie 18,819.9 ha) of the total land area. Other negligible value habitats, ie Landfill and Rural Industrial Storage/Containers, presented much lower percentage cover values of 0.36% and 0.90%.
Changes in habitat areas ranged from 0.01% (Mixed Shrubland) to 594.8% (Plantation or Plantation/Mixed Forest) (Table 9.2a). Although there was only a small area of plantation mapped using satellite imagery and aerial photos, a considerable area of plantation (about 154 ha) was picked up during field surveys and marked onto the habitat map. The majority of the habitats have their total area changed slightly (< 2%).
While a total of about 206.4 ha of sandy shore habitats were mapped as spatial components, the majority of the habitat was represented as a linear component. The coastline of Hong Kong is mainly composed of rocky shore which constituted a percentage length cover of 62.3%. Artificial Rocky/Hard Shoreline showed a total length of 273.2 km and comprised 24.0% of the total shoreline. Sandy Shore showed the lowest percentage length cover, ie 13.7%, and had a total length of 156.4 km.
As the habitats are mapped in the form of polygons with an accuracy level of ± 20 m (as required by the Study Brief), there are situations where habitat polygons do not exactly match with the coastline (eg Yung Shue O). However, the "discrepancy" between the habitat edge and the coastline has not been corrected as all the "discrepancies" detected are less than the required level of mapping accuracy, ie 20 m. Gaps between habitat areas and the coastline have been assigned the habitat category of the largest adjoining habitat.
Table 9.2a Area Mapped Before and After Field Surveys for Each Habitat Type, their Percentage Change and Final Percentage Cover |
Type |
Pre-Survey Area(ha) |
Post-Survey Area(ha) |
Percentage Change(%) |
Post-survey% Cover |
| Grassland |
26,119.9 |
26,081.3 |
-0.15 |
23.4 |
| Other |
18,757.2 |
18,819.9 |
+0.33 |
16.9 |
| Lowland Forest |
18,333.4 |
18,225.4 |
-0.59 |
16.3 |
| Mixed Shrubland |
16,476.2 |
16,477.7 |
+0.01 |
14.8 |
| Shrubby Grassland |
8,695.2 |
8,702.8 |
+0.09 |
7.8 |
| Baeckia Shrubland |
6,000.4 |
5,976.9 |
-0.39 |
5.4 |
| Cultivation |
4,281.1 |
4,381.0 |
+2.3 |
3.9 |
| Modified Watercourse |
2,809.5 |
2,827.0 |
+0.62 |
2.5 |
| Fishpond/Gei Wai |
1,892.9 |
1,835.7 |
-3.0 |
1.6 |
| Intertidal Mudflat |
1,640.2 |
1,563.9 |
-4.7 |
1.4 |
| Bare Rock or Soil |
1,442.3 |
1,440.0 |
-0.16 |
1.3 |
| Freshwater/Brackish Wetland |
1,172.4 |
1,030.5 |
-12.1 |
0.92 |
| Rural Industrial Storage/Containers |
1,012.2 |
1,007.7 |
-0.44 |
0.90 |
| Golf Course/Urban Park |
1,002.3 |
1,006.7 |
+0.44 |
0.90 |
| Natural Watercourse |
814.3 |
783.4 |
-3.8 |
0.70 |
| Landfill |
397.2 |
397.7 |
+0.11 |
0.36 |
| Mangrove |
281.3 |
326.5 |
+16.1 |
0.29 |
| Quarry |
220.7 |
228.9 |
+3.7 |
0.20 |
| Sandy Shore (spatial) |
156.8 |
206.4 |
+31.7 |
0.18 |
| Plantation or Plantation/Mixed Forest |
25.9 |
180.0 |
+594.8 |
0.16 |
| Fung Shui Forest |
82.3 |
111.7 |
+35.7 |
0.10 |
| Montane Forest |
60.4 |
59.6 |
-1.3 |
0.05 |
| Seagrass Bed |
26.6 |
41.1 |
+54.7 |
0.04 |
| Rocky Shorei |
712.2 |
709.9 |
-0.33 |
62.3 |
| Artificial Rocky/Hard Shorelinei |
276.2 |
273.2 |
-1.1 |
24.0 |
| Sandy Shore (linear)i |
150.7 |
156.4 |
+3.8 |
13.7 |
| Total (spatial): |
111,700.7 |
111,711.8 |
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| Total (linear): |
1,139.1 |
1,139.5 |
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i: The habitat was mapped as a linear component, the pre- and post-survey "area" is represented by the length (km) of the habitat. (Those sandy shores which have widths greater than 20 m were mapped as polygons (ie spatial in nature)). "Post-survey percentage cover" was calculated based on the length of the habitat relative to the total length of the three linear habitats (ie Rocky Shore, Artificial Rock/Hard Shoreline and Sandy Shore).
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