Conserving biodiversity and the recognition of heterogeneity in ancient landscapes: A case study from south-western Australia

Subdued topographical relief is a conspicuous feature of the temperate High Rainfall Zone (HRZ) of Western Australia, where biotic assemblages are dominated by regionally common eucalypt taxa. These two features have led to the perception of this area as a relatively homogeneous forest, and the establishment of broad-scale management regimes. Examination of the biota at a different scale reveals both exceptional landscape richness, and local endemism of vulnerable taxa. We consider patterns of distribution of a range of the biota including widespread dominants and local endemics. The ancient south-western landscape harbours pockets of refugial habitat and relictual taxa that are dependent on fine-scale hydrological patterns persisting at a local level. These sites are not always predictable from current knowledge of the biota. This suggests a need to reconsider both conceptual frameworks, and conservation priorities in the temperate HRZ. The maintenance of microhabitats that are dependent on moisture, and an even hydrological regime should be key features of management practice. The loss of heterogeneous environments and the difficulty of reconstructing ecosystem functions in the nearby Transitional Rainfall Zone (TRZ) urges a pro-active approach in the prevention of ecosystem decline rather than post-hoe attempts at reconstruction. Thus the interactions between various agents of disturbance must be recognised, in conjunction with a cautious approach to management in the HRZ. Many elements, particularly local endemics, will only survive if complex interactions between agents of disturbance are recognised, and high value is placed on vulnerable, locally endemic taxa.