Burning the bush and biodiversity

Understanding fire and fauna in the Mallee: It’s not rocket science, it’s more complicated than that.

Prof Michael Clarke, Dept of Zoology, La Trobe University

Ecological fire management in Australia is often built on a basic assumption that if one aims for a mosaic of different vegetation types and seral stages in a landscape, the needs of animals will be met. However, this assumption has rarely been tested and there is little evidence to define the characteristics of desirable or undesirable mosaics. We undertook a multidisciplinary study of the responses of a range of taxa (birds, mammals, reptiles, plants and key invertebrates) to fire in the Murray Mallee region of SA, NSW and Victoria. We compared the animal diversity of 28 landscapes (each 12.6 km2  in area) exhibiting differing levels of pyrodiversity at a range of spatial scales. This required sampling fauna, flora, habitat characteristics and fire history at both the landscape and the site level (n = 280 pitfall lines, 560 bird survey points) over a period of two years. Our large scale space-for-time substitution approach enabled us to identify and compare the habitat characteristics and fauna at sites spanning a century-long post-fire time-frame. We found no evidence of increased faunal diversity being associated with an increased diversity of fire age classes at the scale of our landscapes, although heterogeneity of fire ages at a regional or landscape management unit scale may be important. We did find that several taxonomic groups exhibited increased diversity as the proportion of the landscape that had not been burnt for at least 35 years increased. Our study has generated region-wide vegetation and fire history mapping, a new method for aging mallee and predictions regarding the likely consequences of increased fire frequency for fauna and key habitat features (e.g. hollow-bearing trees). Such insights will inform the management of mallee ecosystems in southern Australia for the future.