WorldView-2 high spatial resolution improves desert invasive plant detection

Sahara mustard (Brassica tournefortii) is an invasive species common to the Mojave and Sonoran Deserts in the southwestern US. Our objective was to assess WorldView-2 (WV2) satellite imagery potential to detect Sahara mustard presence, cover, and biomass. We compared WV2 images (2.4 m and 30 m resolution) to Landsat ETM+ image both classified using a mixture tuned matched filtering (MTMF). A total of 1,885 field plots (30 × 30 m) were established across a 8,715 km² study area in spring of 2012, an exceptionally dry year. Average target canopy cover (7.5 percent) and biomass (0.82 g/m²) were extremely low. The WV2 MTMF classification had a much greater overall accuracy of 88 percent, while the resampled WV2 and the Landsat ETM+ MTMF classification overall accuracies were 67 percent and 59 percent, respectively. Producer’s and user’s accuracies in target detection were 86 percent and 94 percent, respectively, although the exceptionally low canopy cover and biomass were not well correlated with image-based estimates.