Saltwater crocodile nesting habitat suitability mapping with Landsat TM and GIS, Northern Territory, Australia

Saltwater crocodile nesting habitat in the coastal rivers and wetlands of the Northern Territory is being mapped through the application of combined remote sensing and GIS methods. The main thrust of the approach adopted is to circumscribe prospective nesting areas as stringently as possible using GIS, thus minimising the spectral range of the investigated regions. Unsupervised classification of Landsat TM data from the prospective areas identified with GIS is then applied. The high-spectral-precision wetland cover classes thus generated are ranked according to nesting habitat suitability by using GIS to calculate the density of previously mapped nests in each class. The classified imagery is converted to a nesting habitat suitability map using the class rankings obtained. Results indicate that successful identification of permanent freshwater bodies is crucial to the effectiveness of the method. The technique may be extended to areas of little or no historical nesting data using class signatures obtained from better known areas. Examples of crocodile nesting habitat mapped using these techniques are presented from three diverse Northern Territory wetland systems: the Finniss-Reynolds floodplain, the Adelaide River and the McArthur River.