Sensitivity of change vector analysis to land cover change in an arid ecosystem

Remote sensing technology can provide timely, accurate information about land cover changes in arid ecosystems particularly vulnerable to human activities. For this study we used decadal Landsat 4 Thematic Mapper (TM) and Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data, to track land cover changes in the arid Pinacate Biosphere Reserve (PBR), Sonora, Mexico between 1989 and 1999. We selected Change Vector Analysis (CVA) to exploit the full range of spectral information contained in the satellite data in order to identify the magnitude and direction of change. We referenced change magnitude and direction to brightness, greenness and wetness axes of the Kauth-Thomas transform. Results are enhanced by incorporating colatitude direction as another vector in the wetness-brightness axis. We found southeast and southwest portions of the study area were changing most rapidly, probably due to grazing outside the PBR. Though no significant changes were detected within the protected area, landscape dynamics exposed with this approach could, however, serve to establish connections with other ecological processes occurring in the PBR.