Can palm date plantations and oasification be used as a proxy to fight sustainably against desertification and sand encroachment in hot drylands?
2019
Mihi, Ali | Tarai, Nacer | Chenchouni, Haroun
Using GIS and remote sensing tools, the current dissertation shows the impact of agricultural mutation in drylands and highlights the effect of date palm (Phoenix dactylifera) plantations (DPP) on desertification phenomenon in oases of the Algerian Sahara Desert. The spatiotemporal survey was conducted using three Landsat satellite images (TM-1984, ETM+-1999, and OLI-2013). Likelihood supervised classification was used to quantify DPP change over three decades, whereas four remote sensed indices were extracted as indicators of desertification process in the study area: Normalized Difference Vegetation Index (NDVI), Normalized Difference Moisture Index (NDMI), Salinity Index (SI-T), and Crust Index (CI). Generalized linear mixed models (GLMMs) were applied to test the effects of year and DPP ‘presence/absence’ for NDVI; year, DPP and NDVI for both CI and NDMI; year, DPP, NDVI and NDMI for SI-T. DPP area and tree numbers quadrupled over the last three decades with a surface increase of 4822ha and more than 0.5 million trees. DPP presence positively influenced NDVI, NDMI and CI, but negatively affected SI-T. Highly significant positive relationships were found between NDVI—DPP, NDVI—NDMI, and NDVI—CI, although negative relationships were obtained between SI-T—NDVI and SI-T—NDMI. DPP areas indicated higher NDVI, NDMI and CI values, but with lower SI-T values compared to the rest of the desert habitats. Our results highlighted the potential role of DPP in controlling and mitigating desertification in hot drylands. This arises from the effectiveness of strategic agricultural policy programs. Landsat series data provided a cost-efficient tool for monitoring change in oases and arid environments.
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