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Degraded or just dusty? 150 years of ecological change in inland eastern Australia

Degraded or just dusty? 150 years of ecological change in inland eastern Australia
Jennifer Lesley Silcock

2014

School of Biological Sciences, University of Queensland, St. Lucia QLD 4072, AUSTRALIA.

ABSTRACT

The ecological history of rangelands is often presented as a tale of devastation, where fragile drylands are irreversibly degraded through inappropriate land-use. There is confusion about how to recognise and measure degradation, especially in low productivity environments characterised by extreme natural variability and where abrupt management upheavals mean that there are few reference sites. These issues have important consequences for rangeland development and management programs, many of which are founded on a perception of serious and ongoing degradation from a former ‘natural’ state. In this thesis, I employ three approaches to assess degradation in inland eastern Australia, part of one of the largest desert landforms in the world and subject to recurring arguments about the cause and magnitude of landscape change since pastoral settlement 150 years ago: written historical records, grazing exclosures, and identification and surveys of rare and potentially sensitive elements of the flora.

From the 1840s, the journals of European explorers provide the first written descriptions of inland Australia. In Chapter 2, I use this record to test prevailing paradigms relating to five key themes of environmental change: vegetation structure, fire regimes, waterhole permanence, macropod abundance and medium-sized mammal assemblages. 4500 observations from fourteen journals spanning twelve expeditions between 1844 and 1919 were geo-referenced. Careful evaluation of the record suggests little change in broad vegetation structure or waterhole permanence, running counter to prevailing paradigms. The sparse observations of fire suggest burning was infrequent, while macropods were apparently uncommon in semi-arid areas where they are abundant today. Systematic evaluation of the explorer record for a region can provide ecological insights that are difficult to obtain by other means. However, there are limitations inherent in the historical record and findings are necessarily broad.