Effect of land-use change on soil erosion potential in the Ahuacatlan River Sub-basin (Nayarit, Mexico)
Description
The evaluated the effect of land-use and land cover change (LUCC) on soil erosion potential in the Ahuacatlán River Sub-basin, located in the state of Nayarit, Mexico, using the Revised Universal Soil Loss Equation (RUSLE) model integrated with GIS tools. The analysis compared data from 1997 and 2021 to identify changes in land use and their impact on erosion dynamics. Results revealed a significant reduction in natural vegetation, particularly oak (Genus Quercus) forests with a decrease of 3,000 hectares and human-induced grasslands that lost 13,000 hectares, alongside an increase in agricultural areas by more than 10,000 hectares. These changes contributed to an increase in erosion potential, with extreme erosion zones expanding by 6,599 hectares, while low erosion areas decreased by 10,695 hectares. Rainfall erosivity (R) and cover management (C) factors were identified as critical drivers of soil erosion, exacerbated by human activities and changing climatic conditions. The findings underscore the need for effective soil conservation practices and sustainable land management strategies to mitigate erosion risks and preserve the ecological stability of the sub-basin. Furthermore, the study offers a comprehensive overview of the situation in the Ahuacatlán River Sub-basin, regarding their erosion susceptibility which may be useful for politicians, planners, and decision-makers in making well-informed decisions.
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For the R factor it was decided to apply the equation developed by Figueroa Sandoval (1991), who associated the regions of Mexico with similar rainfall conditions, from which 14 regions were obtained through a linear regression analysis; this equation does not need information on hourly rainfall intensity, it only needs average annual rainfall to estimate rainfall erosivity. The Ahuacatlán River sub-basin corresponds to Region 10 located in the Pacific Ocean. The precipitation values provided by the SMN-CONAGUA (2020) meteorological stations were used, which correspond to the average annual precipitation in millimeters for the period 1971-2000 and 1991-2020 recorded at the stations near the study area. An interpolation was carried out using the Kriging method, which allows perceive the level of similarity that exists between a pair of points based on the distance that exists between them (Cisneros-Iturbe et al., 2001). The purpose of this interpolation was to generate a map of the annual precipitation for the Ahuacatlán River sub-basin using the precipitation values of each meteorological station in order to apply the R factor formula. The K factor was calculated following recommendations of Sharpley & Williams (1990). The data used for this factor was compiled from the digital map of soils of the world, prepared by the FAO & UNESCO (2007). All these contents are presented in percentage (%) and correspond to the values measured in the topsoil layer. The C factor is assigned to reflect the effect of vegetation and management practices on erosion rates. This factor indicates how vegetation will affect the average annual erosion rate, and how potential soil loss will be distributed over time during changes in land use (Montes-León et al., 2011). For a standard condition, that is, without vegetation cover, the value of C will be equal to the unity and will be assigned the value 1. As the vegetation cover is greater, the value of C is increasingly lower, so the range for this parameter goes from 0 (corresponding to a fully protected land) to 1.0 (for land without any protection). To calculate this factor, the methodology developed by Montes-León et al. (2011) was used, which assigns a value between 0 and 1 according to the types of vegetation cover that occur in Mexico. The data used for this factor were the land use and vegetation maps series I (1997) and VII (2021), these were reclassified into 12 new classes.