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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

4.0 Rare, Uncommon or Restricted Vegetation Communities

Under Criterion B1 (Places possessing uncommon, rare or endangered aspects of Australia's natural or cultural history) an analysis of rare, uncommon or restricted vegetation communities has been undertaken.

The scale of interpretation of such an analysis is clearly a major contributing factor to the result. This analysis has taken national and regional scale perspectives.

4.1 National Perspective

In a national context there are a number of broad scale community types that are naturally restricted or diminished and so can be considered nationally rare or uncommon. In some instances Cape York Peninsula has a good representation of these communities. Perhaps the clearest example is that of the closed forest or rainforest communities throughout Australia. These have been identified as very limited, totalling only about 20 000 square kilometres over the continent, yet forming a very rich component of the Australian flora and consequently of high conservation value. About one fifth of Australian rainforest is found on the Peninsula.

Some of the Peninsula's rainforest communities, particularly the mid-Peninsula forests, are regionally common, but this does not diminish their status as nationally rare vegetation communities. The value of undisturbed forest communities is even more significant when considered in a national context. The majority of closed forests on the Peninsula are essentially undisturbed.

Similarly heath communities are very restricted throughout Australia. An examination of the national scale mapping (AUSLIG 1990) indicates that these communities on Cape York Peninsula are among the largest in Australia. Substantial areas of heath are restricted and uncommon in the Australian context and again the Peninsula heaths are largely undisturbed.

Figure 4.1 shows the nationally significant rainforest and heath communities.

4.2 Regional Perspective

Regionally rare or uncommon vegetation communities on Cape York Peninsula were identified through comparing the total cover and number of occurrences of each vegetation community found on the Peninsula. The analysis was undertaken using the Neldner and Clarkson (1994) 1:250,000 vegetation mapping for the Peninsula. This mapping recognised 201 native vegetation units, or different vegetation classes. These classes were also amalgamated into 30 Broad Vegetation Groups (BVG). The Classification into classes and groups was on the basis of vegetation structure (e.g woodland, heath, open forest) and then the floristics (or species composition).

Separate analyses were conducted at the vegetation class and BVG levels. The scale of mapping is important in any map unit based analysis; by doing the analysis at two scales it is possible to effectively test the sensitivity of the analysis to scale issues. The detailed rule set for determining Rare and Uncommon for each scale of analysis is as follows (and is spelt out in more detail in Appendix 3).

For BVGs:

For the 201 classes:

The Neldner and Clarkson vegetation mapping has the complication that individual mapped units (or polygons determined from air photo interpretation) may not necessarily be composed entirely of one vegetation class. However, for each polygon, the relative proportion (in 10% classes) for each vegetation class present within the polygon is given. Thus total areas of vegetation communities have been calculated using the proportion of polygon area occupied by a particular vegetation community. In total Neldner and Clarkson mapped 17,444 polygons. Where rare or uncommon vegetation classes or groups are mapped (Figures 4.2 and 4.3) an indication is provided as to the proportion of a polygon covered by rare or uncommon vegetation.

In addition to the area criteria described above, consideration was given to identifying those vegetation classes that only occur in a few separate places. Restricted vegetation classes, within the CYPLUS study area, were identified as those that occurred in thirty or less polygons, while limited communities occurred in sixty or less polygons.

4.2.1 Discussion

The tables in Appendix 3 indicate the vegetation classes on the Peninsula that are significant because they are regionally rare, uncommon, restricted or limited. In figures 4.2 and 4.3 areas shaded as having more than 30% of a polygon comprising a rare, uncommon or restricted community are those of greater significance.

The difference in the analysis between the BVG and 201 Veg class analysis indicates the importance of detailed interpretation of particular areas. An example is the Kimba Plateaux, which is common in the BVG analysis and rare in the 201 class analysis. For the purposes of this discussion the 201 class analysis is considered more closely.

In interpreting the map there are clearly some areas of particularly high significance. The mid-Peninsula rainforests, Wet Tropics, Lockerbie and Torres Straits Island areas are clearly of importance. The coastal communities along the west coast and the Princess Charlotte Bay areas and the Virilya area to the north west are also consistently of interest. The Wet Tropics is a particular case as the majority of the biogeographic region is to the south of the project area and it is more meaningful to consider the vegetation classes in this area in that context. However, as mentioned above, tropical rainforests are a rare and highly significant community on a national and international level.

As would be expected, the more uniform communities that extend across the central southern Peninsula are not identified as uncommon. What is not expected however is that areas to the south west are identified in the BVG level analysis as being uncommon. It should be borne in

mind, that the boundaries of the study area in the south will to some extent be biasing this result as the Gulf Biogeographic region will likely include areas of these vegetation communities.

Interpretation of the results needs to be undertaken using both the presented plots and the tables provided. For the purposes of this analysis rare, uncommon and restricted communities covering greater than 30% of the identified polygons at either the BVG or 201 class level are considered areas of conservation significance.

However, in determining the impact of a proposed land use or the suitability of any area for a specified land use the data sets would need to be interrogated more closely in those areas where <30% of the identified polygons are identified communities. In any of these polygons there may be the location of a rare or restricted community which is only mapped as a small proportion of the polygon.

A consideration of threatening processes and associated threatened communities has not been undertaken as part of this analysis but should be incorporated in any future planning process.