Complex land cover change processes in semiarid Mediterranean regions: An approach using Landsat images in northeast Spain

In this study we used Landsat images to analyze land cover change processes since 1984 in the middle Ebro valley (Spain). The purpose was to identify abrupt changes suggesting modification of the land cover category, and gradual changes not associated with a change in the land cover type but potentially indicative of significant changes in natural areas. The results showed that: i) in analysis of land cover change the seasonality of vegetation cover is an important factor that must be taken into account in identifying the various change processes that may affect a region; ii) the major land cover changes in the study area were related to very diverse processes including urban expansion, industrial activities, the establishment of land irrigation, land extensification, natural revegetation following rural abandonment, forest fires, and changes in natural vegetated areas related to global warming and drought. With the exception of the occurrence of forest fires, the changes in natural areas (forest, shrubs and steppes) tended to be gradual with respect to both positive (forest colonization following rural abandonment and land extensification) and negative (land degradation and forest decline) processes. These areas showed rates of change that were lower in magnitude than those directly transformed by human activities. We found that time series of high spatial resolution satellite images and the application of change statistics provided a useful approach to the identification of abrupt changes, and gradual land cover change processes that are not commonly revealed using classical analytical approaches.