The international symposium 'HighLand2006', held in Mekelle (Ethiopia), from 21 to 25 September 2006,
was the second time that Ethiopia could host a major international scientific event on geomorphological
processes. HighLand2006 created a forum for those conducting research on the impacts of environmental
change on geomorphic processes and land degradation in East African highlands as well as in similar regions
around the globe. Discussions of results and exchange of experiences during indoor sessions as well as
excursions have resulted in this distinctive set of scientific papers.
The two main questions addressed in this special issue, through case studies in tropical mountain areas on all
1. How have environmental changes impacted the type and intensity of geomorphic processes in tropical
mountains since late Pleistocene times? The answer to this question is strongly linked to our knowledge onchanges
in climate, vegetation cover, human activities, hydrology, hillslope and fluvial processes for such environments.
2. Which factors control the intensity of land degradation, its on-site and off-site impacts in tropical
mountains? This question addresses the role of natural and anthropogenic factors in the degradation of the
vegetation cover and in controlling the intensity of hydrological processes, soil erosion, landsliding, reservoir
sedimentation and flooding.
In parallel with this special Catena issue, a number of selected papers on land degradation and its mitigation
in tropical highlands are presented in a special issue of Soil & Tillage Research.