Rainfall patterns of Algerian steppes and the impacts on natural vegetation in the 20th century

• Published in: Journal of arid land Vol. 10; no. 4; pp. 561 - 573
• Main Authors: Belala, Fahima, Hirche, Azziz, Muller, Serge D, Tourki, Mahmoud, Salamani, Mostefa, Grandi, Mohamed, Ait Hamouda, Tahar, Boughani, Madjid
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.08.2018; Springer Nature B.V
• Subjects: 20th century; Algeria; anthropogenic activities; Anthropogenic factors; arid lands; Arid regions; Artemisia herba-alba; bioclimate; Bioclimatology; Change detection; Climate; Climate change; Degradation; Desertification; Dominant species; Drought; Earth and Environmental Science; Ecology, environment; Ecosystems; Environmental Sciences; Geography; Global Changes; High plains; Human influences; Landscape; landscapes; Life Sciences; Meteorological data; Natural vegetation; New records; Pasture; pastures; Physical Geography; Plains; Plant cover; Plant Ecology; radiative forcing; Rain; Rainfall; Rainfall distribution; Salsola vermiculata; Spatial distribution; Stations; Statistical analysis; Statistical methods; Steppes; Stipa tenacissima; Sustainable Development; time series analysis; Vegetation; Vegetation cover; Algeria; North Africa; climate; rangeland degradation; drought; arid and semi-arid regions; human impact
• ISSN: 1674-6767; 2194-7783
• DOI: 10.1007/s40333-018-0095-x

Since 1960, the steppe regions of North Africa have been subject to an increasing desertification, including the degradation of traditional pastures. The initially dominant species ( Artemisia herba-alba, Lygeum spartum and Stipa tenacissima ) declined and were progressively replaced by other species ( Atractylis serratuloides and Salsola vermiculata ) that are more tolerant to the new conditions. It is not clear whether these changes are due to anthropogenic reasons or climatic determinism. We have carried out a statistical analysis of the climate to detect putative rainfall changes during the 20 th century in the Algerian steppes based on data from 9 meteorological stations, including 2 Saharan stations (El Oued and Touggourt), 3 pre-Saharan stations (Biskra, Laghouat and Ain Sefra) and 4 steppe stations (Djelfa, Saida, Méchéria and El-Bayadh) located in the arid high plains, which represent the bioclimate diversities of the region. Previous studies suggested that significant rainfall changes for the 20 th century only had records in the south of the Oran region. Most of the studies, however, looked at restricted territories over limited periods, and did not integrate the rainiest period 2004–2014. Our work is designed to integrate all the longest time series of meteorological data available for the steppe regions of Algeria. Our results confirm the spatial rainfall distribution (significant rainfall changes only recorded in the southwestern region) evidenced by previous studies, and reveal a decreasing rainfall gradient from northeastern to southwestern Algeria. Moreover, the results reveal a trend of significant decrease of rainfall in the southern Oran region, marked by two drought periods in 1980–1985 and 1999–2003. However, with the exception of the southwestern region, rainfall overall has not declined since the beginning of the 20 th century. While less marked in other regions, the drought appear to have affected all territories of the Algerian steppe. Consequently, our study implies that the climate was not a leading influence in the on-going degradation of the vegetation cover of steppe landscapes. Such a vegetation evolution thus appears to be have been determined more by human activities than by climate forcing.