Monitoring the change of Phragmites distribution using satellite data

Walpole Island in southern Ontario has extensive cattail marsh. In recent years, however, an invasive species (Phragmites) is fast spreading in this area and is affecting the ecosystems and wildlife habitat. In this research, a series of optical satellite images, including Landsat thematic mapper (TM), Satellite pour l'Observation de la Terre (SPOT), and Indian Remote Sensing Satellite (IRS), were used to monitor the recent growth of Phragmites and locate the areas subject to the highest rate of loss of cattail. The post-classification comparison method was applied for change detection. The change-detection accuracy is highly dependent on the accuracy of the classification of the images involved in the process. To improve the results, classification was performed on the combination of spectral bands and textural features. Employing a texture analysis technique, a RADARSAT image was used to resolve the effect of cloud cover on the classification result of the Landsat image. Maps showing the change of Phragmites distribution were created for different years. The change maps showed areas experiencing the highest rate of change in the study area. This work shows that remote sensing can provide important information for wetland vegetation changes.