DOI: 10.2478/jwld-2018-0002 © Polish Academy of Sciences (PAN), Committee on Agronomic Sciences JOURNAL OF WATER AND LAND DEVELOPMENT Section of Land Reclamation and Environmental Engineering in Agriculture, 2018 2018, No. 36 (I–III): 17–26 © Institute of Technology and Life Sciences (ITP), 2018 PL ISSN 1429–7426 Available (PDF): http://www.itp.edu.pl/wydawnictwo/journal; http://www.degruyter.com/view/j/jwld Received 20.04.2017 Reviewed 29.06.2017 Accepted 04.08.2017 Assessment and mapping of desertification A – study design B – data collection sensitivity with MEDALUS model and GIS – C – statistical analysis D – data interpretation E – manuscript preparation Case study: basin of Hodna, Algeria F – literature search Fouzia BOUDJEMLINE1) ABCDEF , Ahcène SEMAR2) ADF 1) University of Sciences and Technology Houari Boumediene, Department of Geography and Spatial Planning, BP 32 El Alia, 16111 Bab Ezzouar, Algiers, Algeria; e-mail: [email protected] 2) National Superior Agronomic School, Department of Soil Science, El Harrach, Algeria; e-mail: [email protected] For citation: Boudjemline F., Semar A. 2018. Assessment and mapping of desertification sensitivity with MEDALUS model and GIS – Case study: basin of Hodna, Algeria. Journal of Water and Land Development. No. 36 p. 17–26. DOI: 10.2478/jwld-2018-0002. Abstract In Algeria, desertification risk is one of the main environmental and also social and economic problems. As much as 20 million hectares of northern Algeria are highly exposed and vulnerable to desertification with large areas falling into his ‘severe’ risk category, because the present massive destruction of vegetation and soils. This study aimed to use geographic information system (GIS) for mapping environmentally sensitive areas to deserti- fication based on Mediterranean Desertification and Land Use (MEDALUS) approach in basin of Hodna, Alge- ria. Sensitivity is estimated with a modification of the MEDALUS environmentally sensitive area index (ESAI) which identifies such areas on the basis of an index (ESAI) that incorporates data on environmental quality (cli- mate, vegetation, soil) as well as anthropogenic factors. This methodology allows the classification of land in critical, fragile and potentially sensitive areas. The results obtained show that 61% of the area is classified poten- tially sensitive to low sensitivity. These areas are particularly located in mountain areas. Spatially, the areas sen- sitive to degradation are as well in the lower region of the Hodna in Highlands consisting mostly of steppe route. The factors that could explain these variations of sensitivity are related mainly to changes in precipitation be- tween the North and the South altitude and pressure of the population and livestock. Key words: Algeria, desertification, ESAI, Hodna River basin, MEDALUS, soil sensitivity INTRODUCTION assessment of desertification [FAO-UNEP 1984], model Turkmenistan [BABAEV 1985], GLASOD The United Nations Conference on Environment [OLDEMAN et al. 1991], MEDALUS [KOSMAS et al. and Development [UNCED 1992], held in Rio (1992), 1999], DPSIR-FRAMEWORK [GIWA 2001] etc. The has defined desertification as being: the degradation main processes of land degradation are related to veg- of land in arid, semi-arid and lands regions dry, due to etation cover, soil quality and erosion [FAO 1984]. various factors, including climate variations and hu- Occur on a given area to certain elements of the natu- man activities. In many countries, desertification is ral ecosystem [soil, vegetation and water] are used one of the most serious problems. Desertification af- beyond their specific thresholds [KIRKBY, KOSMAS fects one quarter of the area of the globe [UNCCD 1999]. This requires a good knowledge of the interac- 2008]. In Africa, more than a billion hectares are tions between the behaviour of economic actors, the moderately or seriously affected by desertification potential of ecosystems and the mode of sharing re- [THOMAS 1995]. Different models have been pro- sources. posed to assess desertification at different scales with BOUGUERRA et al. [2017] proposed a minimum different approaches and settings methodology for data set for characterizing and monitoring soil indica- © Polish Academy of Sciences (PAN) in Warsaw, 2018; © Institute of Technology and Life Sciences (ITP) in Falenty, 2018 18 F. BOUDJEMLINE, A. SEMAR Fig. 1. Presentation and hypsometric map of the basin of Hodna; source: own elaboration tor. Quantitative indicators of soil includes soil attrib- their interannual variability and during the same sea- utes and properties such as rainfall erosivity factor son (increase in inter- and intra-annual) [ROUSSET, (R), topography (LS), soil erodibility (K), cover- ARRUS 2004]. management (C) and support practice (P). The estimate of sensitivity to land degradation in In general, it is currently accepted that desertifica- the Hodna basin was based on the model developed tion is better explained by the combination of the so- under the Mediterranean Desertification and Land Use cio-economic factors and biophysical, rather than fac- (MEDALUS) project. DISMED [2003], mention that tors by a simple variable [LAMBIN et al. 2009]. More- adapted to the conditions of Mediterranean environ- over, the reduction in precipitation can activate some ments, the model served as the basis for work in sev- indirect causes of desertification through changes in eral countries such are (Portugal, Spain, Italy and land use [LAMBIN et al. 2009]. Greece, Algeria, Egypt, Libya, Morocco, Mauritania, Many scientists agree that desertification is main- France, Tunisia and Turkey). ly due to human activities [CORNET 2001; KATYAL, In this article, the main objective is; the stratifica- VLEK 2000; LE HOUÈROU 1968; WARREN, AGNEW tion of the territory of the watershed in areas that are 1988]. However, the results of recent research on differentiated according to their degree of sensitivity global climate change and the Mediterranean in par- to desertification. The approach is based on the use of ticular tend towards a reduction in annual rainfall, an GIS in the MEDALUS model applied to the basin of increase in average temperatures and an increase in Hodna, Algeria. © PAN in Warsaw, 2018; © ITP in Falenty, 2018; Journal of Water and Land Development. No. 36 (I–III) Assessment and mapping of desertification sensitivity with MEDALUS model and GIS… 19 MATERIALS AND METHODS SQI = (ST ∙ PM ∙ S ∙ D ∙ SD)1/5 (1) 1/3 STUDY AREA CQI = (PP ꞏ IA ꞏ OR) (2) VQI = (FR ∙ EP ∙ DR ∙ PC)1/4 (3) The Hodna basin is approximately 250 km south- 1/4 -East of the capital, Algiers. It is located between AQI = (APG ∙ DP ∙ DR ∙ DL) (4) 36°11' and 34°29' N latitude and between 3°2' and Where: ST = soil texture, PM = parental material, S = 6°11' E longitude (Fig. 1). The basin straddles two slope gradient, D = drainage, SD = soil depth, PP = distinct geological and geomorphological domains. annual precipitation, IA = aridity, OR = field orienta- To the north and north-east is the Tellian Atlas and to tion, FR = fire risk, EP = erosion protection, DR = the South, the Saharan Atlas. The area of the Hodna 2 drought resistance, PC = plant cover, APG = annual basin is 26 500 km . The situation of the Hodna basin population growth rate, DP = density of the popula- between two series of mountains to the North and the tion, DR = density of the road network, DL = density South organizes the basin around a closed almost flat of livestock. basin at an altitude of 400 m, and which receives the flow of surface waters in the region. At the centre of A score is assigned to the elements of a particular this basin, the Chott El Hodna has an area of 1 150 km2. parameter in relation to their effect on the sensitivity The particularly mountainous northern slopes of to soil degradation and desertification processes as the Hodna basin are subject to the Mediterranean cli- described by KOSMAS et al. [1999]. Scores for soil, mate influences, which explain a relative abundance climate, vegetation and anthropogenic factors are re- of rainfall that varies between 400 and 800 mm. The ported in tables 1, 2, 3 and 4. presence of important forests of oaks, cedars and pines of Aleppo is also explained by these topograph- Table 1. Classes and indices weights to assign different ic and climatic conditions favourable. The southern parameters used for the assessment of soil territories of the Hodna basin are however subject to Factor Class Description Characteristic Index the Saharan influences from the south. Their average 1 good L, SCL, SL, LS, CL 1.0 annual rainfall varies between 100 m and 150 m 2 moderate SC, SiL, SiCL 1.2 Texture across the basin. At the basin scale, the average rain- 3 poor Si, C, SiC 1.6 fall of the basin is between 200 and 350 mm (rainfall 4 very poor S 2.0 map of the Hodna to 1:1 000 000) (National Agency shale, schist, basic, ultrabasic, of the Hydraulic Resources – Fr. Agence Nationale 1 good 1.0 conglomerates, des Ressources Hydrauliques – ANRH, 1967–2014). unconsolidated It is also characterized by high temperatures in sum- Parent limestone, marble, mer and low in winter. The lowest temperature is material granite, rhyolite, 2 moderate 1.7 reached during the month of January with a value of ignimbrite, gneiss, 3.6°C and 4.02°C, while the maximum is 38.8°C and siltstone sandstone 3 poor 2.0 39.22°C in July or Two M'sila station, Bou-Saada marl, pyroclastics (National Meteorological Office – Fr. Office National very gentle 1 <6% 1.0 de la Météorologie – ONM, 1988–2014). to