Use of high-resolution imagery to map wetland environments in south-central Ontario, Canada

Abstract

Wetlands within the Great Lakes basin are among the most productive ecosystems in this region of North America. They provide habitat for many species of plants, fish, waterfowl and other wildlife. Acting as natural water purification systems, wetlands also filter contaminants and excessive nutrients. Despite the many functions and values of these ecosystems, human activities over the past 200 years have resulted in significant wetland degradation and loss within the Great Lakes basin. Wetland managers have identified the need to produce a detailed and accurate digital database of these ecosystems in order to better map and monitor their changes. To provide the detail that is necessary for management decisions, high-resolution imagery is often required. The overall goal of this study is to develop improved methods for wetland monitoring and management in Ontario. A specific objective of this is to investigate the capabilities of the Compact Airborne Spectrographic Imager (CASI) and Ikonos-2 sensors to provide detailed information on wetland vegetation and adjacent land-use/land-cover types in a shoreline wetland and in a series of inland wetland complexes located in south-central Ontario. In particular, the question arises as to what extent these data can be used to meet the operational mapping and monitoring requirements of governmental and nongovernmental agencies responsible for wetland management within this region. Spatial- and spectral-mode CASI as well as Ikonos-2 data were acquired over the selected study sites during the year 2000 growing season. Standard image analysis techniques were used to determine the information content of these data. Results to date indicate that high-resolution data can provide detailed information about wetlands and adjacent land-use and land-cover types. The most useful and accurate results were obtained by applying a maximum-likelihood classifier to selected green, red and near-infrared bands of the spatial-mode CASI data. These data permitted the greatest differentiation between vegetation types, particularly within the inland wetland site. Using these data, it was also possible to distinguish shallow open water and submergent aquatic communities, a task that has been difficult to accomplish with broad-band satellite data (e.g. Landsat TM). Discussions with resource managers indicate that the results of this study are useful to agencies responsible for wetland management in Ontario.