Get access

Monitoring an invasive perennial at the landscape scale with remote sensing


  • Roger A. Lawes,

  • Jeremy F. Wallace

  • Roger Lawes is a Research Scientist with CSIRO Sustainable Ecosystems (Davies Laboratory, Townsville, Qld 4814, Australia), as well as the CRC for Australian Weed Management. (Present address: CSIRO Sustainable Ecosystems, Centre for Environment and Life Sciences, Floreat, WA 6151, Australia; Tel. +61 8 93336455; Email: Jeremy Wallace is a Remote Sensing Scientist with the CSIRO Mathematical and Information Sciences (Leeuwin Centre for Earth Sensing Technologies, WA 6151, Australia). This study was undertaken to monitor the invasion of Prickly Acacia across the Mitchell Grass Plains of Central Queensland using temporal sequences of Landsat imagery.


Summary  Worldwide, invasive weeds threaten agricultural, natural and urban ecosystems. In Australia's agricultural and grazing regions, invasive species often establish across extensive areas where weed management is hampered by an inability to detect the location and timing of an outbreak. In these vast landscapes, an effective detection and monitoring system is required to delineate the extent of the invasion and identify spatial and temporal factors associated with weed establishment and thickening. In this study, we utilize a time series of remote sensing imagery to detect the spatial and temporal patterns of Prickly Acacia (Acacia nilotica) invasion in the Mitchell grass plains of North Queensland. We develop a spectral index from Landsat images which is applied to images from 1989 to 2004, in combination with a classification mask, to identify locations and monitor changes in Prickly Acacia density across 29 000 km2 of Mitchell grass plains. The approach identified spectral and temporal signatures consistent with Prickly Acacia infestation on 1.9% of this landscape. Field checking of results confirmed presence of the weed in previously unrecorded locations. The approach may be used to evaluate future spread, or outcomes of management strategies for Prickly Acacia in this landscape and could be employed to detect and monitor invasions in other extensive landscapes.