Agricultural development of the Anti-Atlas: From desertion to risks of soil degradation and landscape heritage

Abstract

The Western Anti Atlas Mountains, located at the South-west of Morocco, have been prone to intense rural migration for several decades. As a consequence, the agricultural terraces built for several centuries on valley walls have been abandoned and degraded. The risks of runoff and erosion are becoming significant both at the upstream and the downstream (flash floods, dam silting). The objective of this work is to introduce this issue. The state of the art was described in the terroirs of Tizerkine and Timzemzit, commune of M’Zal, province of Chtouka-Ait Baha.Following the characterization of soil surface conditions of the terraces, the status of erosion and the risk of runoff were appraised according to the age of terrace abandonment. Erosion was appreciated by estimating the "soil surface factor, SSF” of PAP/CAR method and the infiltration rate was measured using double rings method. The results showed that the abandonment of terraces has led to the reduction of surface vegetation cover, the decrease of surface openings (soil sealing) and to soil compaction. The differences are significant as of the first year and the risk of runoff was high. A year of abandonment caused the soil surface to lose 40% of its infiltration capacity. At the end of 5 years abandonment, the infiltration rate has been reduced to 1/3. The retaining walls of terraces deteriorated gradually with the age of abandonment. More than half (57 %) of the surface of valley walls terraces experienced moderate to high water erosion, and severe forms of erosion have already been present. More than 11% of the surface has been strongly degraded after 20 years of abandonment. Therefore watershed upstream risks to lose its soils and its scenery, and the downstream are likely to suffer devastating floods. Landscape inheritance made up of these arranged valley walls are being lost. Thus a meticulous attention must be given to these landscapes to better understand their socio-economic and agro-ecological functioning and to better rehabilitate and preserve them. For instance, the introduction of payment for environmental services (PES) could help to rehabilitate the agricultural terraces of the Anti-Atlas.

Key words: Terraces, Abandonment, Degradation, Infiltration capacity, Water erosion, Anti-Atlas, Morocco