Open Cut » Environment
Over the last three-decades there have been multiple instances of unexplained widespread decline and death of native and exotic pasture grass species in northern, central, and southern Queensland. A causal link between previous cases, known as Buffel Dieback (BD), and current (post-2016) cases, known as Pasture Dieback (PD), has yet to be established. While research on the PD causal agents is ongoing, there has been limited work characterising the environmental drivers of PD, its spatial spread patterns, and trajectory of recovery of impacted areas.
This project assessed aerial imagery from 13 different mine sites, representing nine different mining companies throughout central and southern Queensland to assess areas for PD occurrence. Imagery included historical as well as current captures, with significant variation in spatial and temporal resolution. The aim of the project was to provide an inventory of PD located within the rehabilitated estate of central and southern Queensland and determine the extent and severity of any PD symptoms and the potential risks to future mine closure. At the time of project establishment, the central and southern Queensland pastoral industry had just experienced an unprecedented wave of PD, impacting an estimated 4.48 million hectares of sown pastures in Queensland.
While studies have aimed to determine the causal effects of PD, there continues to be debate over the environmental drivers and a knowledge gap on the spatial spread patterns and subsequent recovery of impacted areas.
This project demonstrates the potential for using high resolution aerial imagery to monitor pasture health by employing red, green, blue indices and automated random forest classifiers and offers valuable new insights into the potential link between environmental stressors and pasture dieback. The focus of this project was at the property scale (1-100ha) and as such data suggests an association between the timing of high winter night-time temperatures, unseasonal winter rainfall and the emergence and subsequent spread of PD. It could be feasible that causal factors may be:
- related to plant stress due to disrupted biochemical metabolic processes,
- favourable conditions for mealy bug breeding and feeding or both these factors.
However, research conducted over the past decade shows that the PD issue is inherently complex, and more research is needed to support the hypothesis. Findings support previous work by MLA and suggest that mine managers can protect rehabilitated pastures by maintaining pasture vigour either through grazing, slashing or low intensity fuel reduction burning and monitoring weather conditions that are favourable to mealy bug populations outbreaks to adjust grazing strategies accordingly.