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Cape York Peninsula Land Use Strategy


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Areas of Conservation Significance on Cape York Peninsula

Cape York Peninsula Land Use Strategy
Abrahams, H., Mulvaney, M., Glasco, D., & Bugg, A.
Office of the Co-ordinator General of Queensland
Australian Heritage Commission, March 1995

Areas of Conservation Significance on Cape York Peninsula

9.0 Areas Significant for Marine Vegetation

9.1 Mangroves

The mangrove communities of eastern Queensland including Cape York Peninsula have been widely studied; for example Dowling and McDonald (1979), Bunt (1982), and Duke (1992) and as part of the CYPLUS NRAP program Danaher (1994). Mangrove areas are important for their ecological role, as these marine plants directly support local and off-shore fisheries through the provision of food, shelter and breeding areas (Danaher 1994).

Duke (1992) provides the global context for the Australian mangrove communities. Mangrove communities are richest in tropical regions with sea temperatures being an important determinant of distribution. The eastern coastline of continents with warmer ocean currents have larger areas, wider distributions and richer mangrove communities than the western coasts with colder off-shore currents.

Similarly species richness generally reduces with distance from the tropics, and this is certainly the case along the east coast of Australia, Cape York Peninsula having over 30 species recorded compared with nine in South East Queensland, and one in Victoria (Duke 1992). As a result many species reach their limit of range progressively further south along the coast.

The mangrove flora of Australasia is one of the richest in the world having around five times greater species diversity than all other regions with the exception of southern New Guinea (Duke 1992). The Cape York Peninsula mangrove communities are therefore among the richest in the world and exhibit a strong zonal pattern (Danaher 1994). Duke (1992) discusses the known disjunctions of mangrove communities in the region which provides an indication of the biogeographic history of mangrove communities. The current limited knowledge of New Guinea mangrove distributions limits a thorough understanding of the evolutionary biogeography however.

The mapping by Danaher as part of the NR06 program (1994) used satellite interpretation to identify fifteen mangrove communities. Table 9.1 shows these communities and the seagrass mapping units also.

Table 9.1 Marine Vegetation Classes (Danaher 1994)

1       Rhizophora                 closed *       
2       Rhizophora                 open           
3       Ceriops                    closed         
4       Ceriops                    open           
5       Avicennia                  closed         
6       Avicennia                  open           
7       Rhizophora/Ceriops         closed         
8       Rhizophora/Ceriops         open           
9       Avicennia/Ceriops          closed         
10      Avicennia/Ceriops          open           
11      Landward Rim               closed         
12      Landward Rim               open           
13      Mixed                      closed         
14      Mixed                      open           
15      Saltpan                    open           
16      Seagrass                   Density        
                                   < 10% of area  
17      Seagrass                   Density        
                                   10-50% of      
18      Seagrass                   Density        
                                   50-100% of     

* Closed communities are those in which the foliage or canopy cover of the mangroves is greater than 70% of the total ground area.

9.2 Seagrasses

Seagrass communities are also important for their ecological and commercial significance. They are particularly important as nursery areas for prawn and lobster fisheries and grazing areas for dugongs (Dugong dugon) and green turtles (Chelonia midas) (Poiner et al 1989). Sea grasses require shelter from high energy waves, light for photosynthesis and minimal exposure to air (Danaher 1994).

The Queensland Department of Primary Industries has mapped and sampled seagrasses along the Queensland coast (Coles et al 1992 and 1985 and Lee Long et al 1993). Danaher (1994) has incorporated their mapping into the CYPLUS NR06 report and GIS coverage. The mapping has a number of limitations, due to the seasonality (extent of seagrass varies with season), depth of survey (only shallow [<20 metre depth] seagrasses have been surveyed) and difficulties of accurate mapping and precise positioning in marine environments (Coles et al 1992).

There are 12 genera and 55 species of seagrass recognised around the world (Larkum & Den Hartog 1980). Mukai (1993) considers the global distribution of seagrasses and concludes the coastal waters of Malesia are the centre of origin for sea grasses and marine currents have been largely responsible for their distribution throughout the Indo-Pacific.

Australia has the highest number of seagrass species of any continent in the world with particular communities being amongst the most diverse in the world (Larkum & den Hartog 1989). With 14 species identified from the Torres Straits and east coast of Cape York (Lee Long et al 1993) this area is clearly a special case in terms of seagrass distribution. Lee Long et al (1993) have grouped the species information into mapping units for the east coast of Australia. Having twelve species, the areas of Barrow Point to Murdoch Point on Cape York Peninsula and Dunk Island to the South of Cairns are the most species rich along this generally rich east coast (Table 9.2). Flinders Island and Princess Charlotte Bay (9 species), Weymouth Bay, Cape Direction, Murdoch Point - Lookout Point and Bedford Bay - Cape Tribulation (8 species) and Escape River Margaret Bay, Bathurst Bay, Ninian River and Cape Flattery (7 species) are all areas notable as species rich areas.

Consideration of areas of particular note for Dugong has been undertaken in Section 17.4 of this report.

9.3 Mangrove and Sea Grass Areas of Conservation Significance.

Danaher (1994) mapped fifteen mangrove communities as part of the CYPLUS NRAP Marine Vegetation Survey (NR06). Neldner and Clarkson - NR01 (1994) also mapped mangrove areas. A direct comparison of data sets was not feasible because different classes were mapped. The Danaher (1994) mapping included both seagrass and mangrove communities and for this reason was most appropriate to use for the analysis and plotting of the results.

The ecological significance of mangrove and seagrass communities makes all areas mapped important. It is however possible to determine those areas on the Peninsula that are of particular note. Danaher has broadly delineated areas of significance for fisheries reserves following a number of criteria (Danaher 1994). These criteria relate to some aspects of the RNE criteria outlined in Table 9.3. The application of the RNE criteria may include other attributes to those of the Fisheries Reserves Criteria or a combination thereof. For example, in determining representative areas (Criterion D), the AHC considers condition and integrity important components: Size (1) and Disturbance History (5) above can be combined to provide a good indication of representative areas.

Table 9.3 Fish Habitat Reserve Criteria - RNE Criteria

Fish                Description             RNE                Description                
Habitat                                     Criterion                             

        1          Size                       D1         Principle Characteristics  
                                                         of Class/                  

        2          Diversity of specific      A3         Richness or diversity      
                   Habitat Features                                                 

        3          Diversity of Pacific       A3         Richness or diversity      
                   marine fauna and flora                                           

        4          Existing of potential      A2         Areas for maintaining      
                   fishing grounds                       existing processes.        
                                                         Breeding and feeding       

        5          Level of existing and      D1         Principle Characteristics  
                   future disturbances                   of Class/                  

        6          Unique features            B1         Rare or Uncommon features  

        7          Protected species          B1         Rare or Uncommon features 

The areas identified as important fish habitat areas (Danaher 1994), are considered to be of natural heritage significance.

The existing Fish Habitat Reserves include:

Danaher recognises additional areas of importance as fish habitat in the areas of:

Additional areas identified on the basis of seagrass species richness (Section 9.2 above) are:

The locations of these areas have been included on the Marine Vegetation coverage (Figure 9.1) and more detailed descriptions for each location can be obtained from Danaher (1994).

In addition to the sites identified by Danaher, parts of Albatross Bay can be considered to have conservation significance in terms of the extent of seagrass beds present and the diversity of mangrove species (17 species are known to occur in the Nature reserve east of Weipa (Paul Warren, COLMALCO, 1995, pers. comm.).