Mapping options to track invasive Phragmites australis in the Great Lakes basin in Canada

Marcaccio, J.V. and Chow-Fraser, P.
Proceedings of 3rd International Conference - Water resources and wetlands.
2016 ISSN: 2285-7923, pages 75-82


We directly compared the performance of four remote-sensing methods for mapping invasive Phragmites in coastal wetlands of Long Point Bay, Lake Erie, Canada. We refer to the first method as Landsat, which uses Landsat images and NDVI (Normalized Difference Vegetation Index) responses from images acquired in multiple years to determine areal cover of Phragmites and other dominant vegetation classes. The second method, which we will call PALSAR (Phase array type L-band Synthetic Aperture Radar) uses radar to aid detection of water level and biomass of Phragmites and other wetland classes. We refer to the third method as SWOOP (Southwestern Ontario Orthophotography Project), which uses spring-time orthophotos and object-based image classification to map Phragmites and other features in a defined region of interest. Our last method is called UAV (unmanned aerial vehicle) which involves manually delineating Phragmites in image data acquired by a UAV. The UAV method was most accurate at identifying Phragmites but could only be used to map a small area. The PALSAR approach provided a more accurate view of invasive Phragmites than did Landsat, and exceeded the SWOOP in terms of accuracy but not in terms of spatial resolution. The best choice of method to use will depend on the scope of the mapping project and available funding. Landsat and PALSAR may be most appropriate for mapping Phragmites at the regional scale, while SWOOP and AUV may be most appropriate for finer-scale updates. To fully interpret the invasion pattern of Phragmites at the scale of the Great Lakes basin, a combination of these methods may be required.