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
2. Executive summary
Several types of refugia are defined to take into account the fact that different concepts may be involved in the idea of a refuge. In evolutionary terms, a refuge is a region in which certain organisms persist during a period in which most of the original geographic range becomes uninhabitable because of climatic change. However, the term refuge may be used in other ways, particularly to mean a region to which species retract for short periods (i.e. for a number of years at the most) when large parts of their preferred habitats become uninhabitable because of drought or other effects. Yet another type of refuge comprises regions to which threatened species have retreated because of environmental changes set in train by European settlement. Our investigations have led us to the following nine categories:
- Mound springs
- Mountain ranges
- Ecological refuges
- Refuges from exotic animals
- Refuges from land clearing
Information on the distribution of plants and animals in arid and semi-arid Australia was surveyed in order to determine the identity and location of foci of biological diversity. Subsequently, this data-set was used to identify locations thought to constitute refugia because they possess unusual aggregations of species considered endemic, relictual, threatened, or otherwise significant. The chief refuge value of each is noted, and comments provided on threatening processes within the refugia, and on land tenure. Although the emphasis of the study, by force of circumstance, is on the species component of biological diversity, the refugia that are identified are likely to incorporate at least some values inherent in genetic and ecosystem diversity.
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 cannot be considered as concrete, objective or final. It is merely a starting-point for discussion.
The number of refugia identified in arid and semi-arid Australia was 76; there were 32 in Western Australia, 13 in South Australia, 14 in the Northern Territory, 8 in Queensland, and 9 in New South Wales. Some refugia possessed values appropriate to more than one category, but when classed according to their primary characteristics the distribution of refugia among the categories was as follows: Islands, 9; Mound springs, 4; Caves, 3; Wetlands, 36; Gorges, 5; Mountain ranges, 12; Ecological refuges, 2; Refuges from exotic animals, 3; and Refuges from land clearing, 2. Our attempt to rank the refugia showed that Wetlands tended to be classed as of lower importance compared to the other categories because they possessed fewer notable species.
A preliminary analysis on a test region of central Australia shows that it would be possible for Landsat imagery to be used to identify areas of persistent vegetational greenness; such areas might function as short-term drought refugia for certain organisms.
Management issues affecting refugia are discussed. It is concluded that they are identical to those facing arid Australia as a whole: land degradation resulting from over-grazing by domestic stock and by feral animals, alterations in hydrology, removal of habitats by clearing at the fringes of the semi-arid zone, depredations by exotic predators, and uncontrolled fire. Thus, better management of refugia is dependent upon mitigation of the same forces operating throughout the landscape, but improved management is especially necessary in these refugia because the organisms within them frequently have no other home.