Abstract
Abstract. Since the turn of the millennium various scientific publications have been discussing a re-greening of the Sahel after the 1980s drought mainly based on coarse-resolution satellite data. However, the author's own field studies suggest that the situation is far more complex and that both paradigms, the encroaching Sahara and the re-greening Sahel, need to be questioned.This paper discusses the concepts of desertification, resilience, and re-greening by addressing four main aspects: (i) the relevance of edaphic factors for a vegetation re-greening, (ii-iii) the importance of the selected observation period in the debate on Sahel greening or browning, and (iv) modifications in the vegetation pattern as possible indicators of ecosystem changes (shift from originally diffuse to contracted vegetation patterns).The data referred to in this paper cover a time period of more than 150 years and include the author's own research results from the early 1980s until today. A special emphasis, apart from fieldwork data and remote sensing data, is laid on the historical documents.The key findings summarised at the end show the following: (i) vegetation recovery predominantly depends on soil types; (ii) when discussing Sahel greening vs. Sahel browning, the majority of research papers only focus on post-drought conditions. Taking pre-drought conditions (before the 1980s) into account, however, is essential to fully understand the situation. Botanical investigations and remote-sensing-based time series clearly show a substantial decline in woody species diversity and cover density compared to pre-drought conditions; (iii) the self-organised patchiness of vegetation is considered to be an important indicator of ecosystem changes.
Highlights
The long-lasting and sometimes heated scientific debates on Sahel greening vs. Sahel browning inspired the author to critically analyse the existing research results from the viewpoint of over 30 years of the author’s own research activities in the African Sahel
This new paradigm is predominantly based on studies using coarse satellite remote sensing data (NOAA-AVHRR) monitoring the period from 1981 until today (Anyamba and Tucker, 2005; Nicholson et al, 2012; Dardel et al, 2014b)
Krings (1980) described the ecological situation in Oudalan, Burkina Faso on the basis of extended field surveys with special emphasis on the remarkable cultural geographical changes in the contact zone of nomadic and sedentary ethnic groups. He visited the region between October 1976 and March 1977 and reported species like Adansonia digitata, Pterocarpus lucens, Commiphora africana, and Guiera senegalensis in the tiger bush formation north of Oursi
Summary
The long-lasting and sometimes heated scientific debates on Sahel greening vs. Sahel browning inspired the author to critically analyse the existing research results from the viewpoint of over 30 years of the author’s own research activities in the African Sahel. The discussion is based on the author’s own research results and contributions that are put into the context of the scholarly debate on the issue. Each section starts with a description of the author’s own contributions followed by an analysis of results from other authors.
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