Resumo:
Information about changes in land use and land cover is useful to address issues related to drylands management, as well as to support decision-making related to the sustainable use of soils. Since drylands are frequently affected by accelerated soil erosion, land degradation and desertification associated with vegetation cover losses, constant monitoring of land use and land cover changes are required. However, land use and land cover maps are often not available, making it difficult to monitor degradation. Therefore, in this work, we developed an efficient mapping method to monitor bare soil areas, which are indicative of land degradation in the case of the Northeast of Brazil, using Normalized Difference Vegetation Index images. The proposed methodology was field calibrated and applied to the region using 17-year (2000–2016) NDVI maps, with a spatial resolution of 250 m. Based on bare soil mapping, we estimated the degree of degradation using an index calculated from the persistence and frequency of bare soil during the study period. The results indicated that the degraded areas increased in the period of the study, mainly in areas of pasture and Caatinga. This expansion has been accelerated due to the severe drought that affected the region since 2011.
