Achim Röder is a senior scientist and lecturer with the Remote Sensing Department, University of Trier, and has been involved in research on desertification and land degradation for more than 10 years. His present research focuses on the characterization of landscape trends using time series analysis, and the derivation of biophysical indicators under consideration of scaling effects and transitions. Joachim Hill has been head of the Remote Sensing Department, University of Trier, since 1994. His research focuses on the application of hyper- and multispectral remote sensing techniques to derive biophysical vegetation parameters and their assimilation in ecosystem models, and on mapping and monitoring land degradation phenomena in dryland ecosystems.