The principle of diffuse to contracted - how modification in the vegetation pattern indicates ecosystem changes. Examples of the African Sahel




15:15 Uhr


Geomatikum H4
Lecture hall H4 (ground floor), University of Hamburg, Bundesstr. 55, Hamburg


Hannelore Kusserow, Institut für Geographische Wissenschaften, Freie Universität Berlin, Germany

The question of assessing land surface changes is essential for understanding ecosystem dynamics. How can we discriminate qualitative changes from fluctuations? Can we identify tipping points, and which indicators are necessary for this purpose? Which regions are hot spots of dramatic changes and what are the impacts on environment and society? Which conflict constellation may result and how to prevent conflicts, induced by ecosystem changes (society-environment interferences) and intensified by climate change? (see also the actual discussion on "Climate change as a security risk" and "Desertification and Security").


Questions like these need to be answered in discussions with policy and decision makers.


This talk deals with ecosystem changes in the Africa’s Sahel Zone, which, due to its large extension, its fast desertification progress and worldwide highest population growth rates, belongs to the moist important climate effective regions in the world and is regarded as a tipping element in the Earth system according to some authors.


Based on long time series (rainfall data, biological data sets) as well as remote sensing data (including aerial photos and satellite images) and long-time ground truth, information on the heterogeneous human-environmental dynamics will be presented.


The problem of differentiating internal variability in an existing dynamic equilibrium from a transition into a qualitatively different state will be discussed. Examples for the process of the system’s recovery from perturbations will be given. The analysis of remote sensing data in combination with long-time series provides the characterisation of different impacts concerning the driving forces (human-environment interface). Based on these data sets it is possible to develop indicators in order to evaluate potential system changes. These data sets can also reveal that a system is approaching a critical threshold. The key indicator in this context is the modification (mainly based on anthropogenic interference) of vegetation pattern in space and time.


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