Soil pedestal dating in the degraded Salitre River basin in the northeast of Bahia, Brazil

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This study evaluated possible causes of degradation of a microbasin (16 ha) in an area of the Salitre River Basin undergoing desertification, in North-eastern Brazil. Interrill erosion in the microbasin was estimated based on measurements of topography, soil erodibility, rainfall erosivity and land use and occupation. The relief was surveyed by an unmanned aerial vehicle, equipped with precision optical meter. Based on the height, position and local erosion around 53 soil pedestals, the year of their origin was estimated, given that these microstructures resist erosion due to the presence of roots. The sediment yield in the microbasin is 71 Mg ha−1 per year. The dating indicates two main periods of pedestal generation: the first, during which 16% emerged, occurred in the 1960s, coinciding with the construction of an unpaved side road in the upper part of the microbasin. The second, in which 80% of the pedestals originated, dates from the 1990s, when there was intense cultivation of Agave sisalana in the region, even on the steep hillslopes. The dating also identified a significant reduction in pedestal formation during the 1980s, a period in which there was a drop in agricultural production of Agave sisalana in the region. Therefore, two development initiatives (the construction of the local road and the implantation of the Agave sisalana monoculture on the hillslopes) are the most likely factors that triggered the desertification in the area.