Análise do cenário de perda de solos e sua contribuição ao risco de desertificação no semiárido brasileiro

Abstract

The soil loss due to water erosion represents one of the main threats to soil health and should be recognized as an urgent issue faced by humanity. Moreover, erosion acts as a contributing factor in the advancement of desertification processes. The Riacho Pontal watershed, located in the semiarid region of Pernambuco, Brazil, has experienced, over the past decades, a worsening of environmental problems, mainly related to soil degradation, such as salinization and, most notably, erosion. Given this context, the following research question was established to guide the development of this study: What is the current estimate of soil loss in the Riacho Pontal watershed, and what are the projections for the future? Thus, the main objective of this study was to assess the relationship between current and future soil loss and to identify the potential contributions to a possible desertification process in the Riacho Pontal watershed, Pernambuco State. To achieve this, geotechnological tools were employed to map soil loss estimates for the year 2023 and to project scenarios for 2060, 2080, and 2100, considering both optimistic and pessimistic conditions. The modeling was carried out through the application of the Revised Universal Soil Loss Equation (RUSLE) within a GIS environment, using ArcGIS 10.8 software. The results indicate a significant increase in the projected soil loss rates, with values exceeding 10 t ha⁻¹ yr⁻¹, particularly in the municipalities of Afrânio and Dormentes (northern portion of the basin), as well as in areas in the southeastern sector (Lagoa Grande) and in Petrolina, where residual landforms such as ridges, hills, mountains, and isolated elevations predominate. Regarding the mapping of current and future scenarios of soil loss contributions to a potential desertification process, the results show an increase in areas classified as having moderate, high, and very high contribution risk over time, in both the optimistic and pessimistic scenarios. In 2023, these areas represented 29.92% of the Riacho Pontal watershed. In the optimistic scenario, projections indicate 37.69% in 2060, approximately 38.53% in 2080, and 36.32% in 2100. In the pessimistic scenario, an increase is also projected: 35.26% in 2060, 36.85% in 2080, and 37.34% in 2100. The areas affected by these contribution risk classes are concentrated in the northern, northwestern, and western portions of the basin, encompassing much of the territory of Afrânio and Dormentes municipalities. To a lesser extent, they also occur in parts of the municipalities of Petrolina and Lagoa Grande. Finally, projections for future scenarios highlight the urgency of restoring areas of Dense/Closed Caatinga vegetation, particularly in the municipality of Afrânio. In these regions, the intensive rearing of sheep, goats, and cattle, combined with charcoal and firewood production, has promoted the removal of vegetation cover, thereby increasing soil loss due to erosion in this part of the basin. Therefore, immediate attention and coordinated actions are required from public authorities, farmers, and livestock producers, through the development of strategies that promote, in the medium and long term, effective alternatives to address the projected conditions.