Monitoring change in the vertebrate fauna of central Queensland, Australia, over a period of broad-scale vegetation clearance, 1973—2002

Abstract

This study reports change in the bird, mammal and amphibian fauna of the Emerald district, central Queensland, as detected from comparison of an inventory study undertaken in 1973–76, with a resurvey undertaken in 2001–02. Over this period, the region was subjected to unusually high rates of vegetation clearance, with the extent of native vegetation declining from 87% to 41%. In Australia, and elsewhere, there are remarkably few such long-term longitudinal studies, and particularly so for those that sample the same sites using identical procedures, and for those undertaken in a region of such dramatic environmental change. The ability to detect change from this dataset is constrained by the relatively small number of survey sites (24–45 survey sites, depending upon the taxonomic group considered). The interpretation of change is also affected by very different climatic conditions between the baseline and resurvey. Higher rainfall in the baseline survey period contributed to the most evident change, a major reduction in the number of waterbirds. However, even with waterbirds excluded, there was a significant change in the bird assemblage across the set of survey sites between the two periods. There were significant increases for a number of typically grassland birds (e.g. red-backed fairy-wren (Malurus melanocephalus), brown quail (Coturnix ypsilophora)) and significant decreases for a range of typically forest or woodland birds (e.g. grey shrike-thrush (Colluricincla harmonica), spiny-cheeked honeyeater (Acanthagenys rufogularis), striped honeyeater (Plectorhyncha lanceolata), grey fantail (Rhipidura fuliginosa)). These changes were largely maintained even when the dataset was restricted to only those sites that remained uncleared: that is, changes were evident not only across the changing landscape as a whole but there were also significant (consequential) changes at uncleared sites. Most of the native mammal species that were recorded sufficiently often to test for change showed a pattern of decline. Again, for some species (pale field-rat (Rattus tunneyi), greater glider (Petauroides volans) and eastern grey kangaroo (Macropus giganteus)), this decline occurred even within uncleared woodland sites. The most notable change in the frog fauna was the major increase in the exotic cane toad (Bufo marinus), but there were also significant declines for two native frog species. These results suggest a general trajectory of decline in distinctive woodland species, and their broad-scale replacement by more commensal species (weedy generalists favoured by human modification of the landscape).