Biodiversity Series, Paper No. 4
S.R. Morton, J. Short and R.D. Barker, with an Appendix by G.F. Griffin and G. Pearce
Department of the Environment, Sport and Territories, 1995
9. The use of information on foci of biological diversity to identify refugia
The data-base gathered together in the previous section will now be used to identify and describe a suite of refugia in arid and semi-arid Australia. In the following sections we summarise the information available for each refuge, noting the Biogeographic Region in which it lies, its approximate size and location, the category to which it belongs (i.e. Islands, Mound springs, Caves, Wetlands, Gorges, Mountain ranges, Ecological refuges, Refuges from exotic animals, or Refuges from land clearing), its chief refuge value, and note the species within it that may be listed by ANZECC and be endemic to the Region under consideration-, relictual or otherwise significant. We also provide brief notes on threatening processes within the refugia and on land tenure.
An attempt is made to provide a measure of the importance of each refuge that might be used to compare among them. As is the case with most ranking procedures, this one is fraught with dangers. It must be seen as a first step only: we emphasise that the measure cannot be considered as concrete, objective or final. We encourage readers to develop their own criteria, and to view our attempt as a starting-point for discussion.
Each refuge was scored as to its apparent importance according to the numbers of species identified as ANZECC-listed, endemic, relictual, or otherwise significant. For each of those classes, we counted the numbers of species within them and scored as follows:
- Number of ANZECC-listed species – 0, 1 (for two or fewer species), or 2 (for three or more species);
- Number of endemic species – 0, 1 (for two or fewer species), or 2 (for three or more species);
- Number of relictual species – 0, 1 (for one to three species), 2 (for three to ten species), or 3 (for more than ten species);
- Number of significant species – 0, 1 (for five or fewer species), or 2 (for more than five species).
The maximum score possible, therefore, was 9. We assigned the scores as follows among three groups of refugia:
- Extremely significant refugia – scores of 7 to 9.
- Highly significant refugia – scores of 4 to 6.
- Significant refugia – scores of 1 to 3.
It can readily be seen that there are numerous grounds for error in this scoring system. It is intimately dependent on the amount of information available; indeed, the greater the information the greater the score. It is also exceedingly scale-dependent; that is, it is likely to produce higher scores for larger areas because they will tend to possess more species of significance. Finally, the issue of scoring raises a difficulty with the concept of a relictual species. Our decision to provide a potentially greater weight for relicts reflects the belief that such species are likely to be major definers of refugia. However, while accumulating the data-base represented by sections 4 to 8, we consistently experienced difficulty in allocating species unambiguously to the relictual category. This was partly due to the fact that two different issues were considered relevant: species that have declined dramatically were considered relictual; but species believed to be evolutionary relicts were also listed here. The latter group causes most problems. Species may be relictual because they have been isolated for long periods and so have speciated; anothers may occur in, say, moist habitats and have much larger sister populations in coastal or near-coastal areas of Australia; and yet others may display disjunct populations not according to "relict" environments but simply because they possess unusual habitat preferences. In virtually no case available to us has a taxonomic group been thoroughly analysed in this fashion, and so our listings of relictual species must be considered preliminary indeed.
All these riders should actively be borne in mind when the measures of refuge significance are inspected.