Agriculture Land Use Change and Demographic Change in Response to Decline Suspended Sediment in Juzna Morava River Basin (Serbia)

This study expounds the dynamic relationships among agricultural land-use change, rural population migration, and sediment transport. The variability of suspended sediment load was detected by Mann-Kendall and Pettitt tests. From 1961 to 2007, the annual trend in suspended sediment concentration and sediment load demonstrated significant reduction (alpha = 0.001), with decreasing rates of 0.0144 g/L/y and 84.7 t/y, respectively. An abrupt change-point was detected in 1984 for the sediment load (p = 0.0001). The double-mass curve method and regression analysis of sediment load versus precipitation were used to quantify the effects of climate change and human activities on sediment load variations. The changes in sediment load were predominantly impacted by human activities (89%), while precipitation explained 11% of the reduction in suspended sediment. An important land-use change recorded in the Juzna Morava river basin comprised the abandonment of agricultural lands due to depopulation processes, as well as economic and social changes, which was followed by significant impacts on soil erosion and sediment transport. Land abandonment was most pronounced in marginal mountain or semi-mountainous areas, where agriculture was until recent decades traditional or semi-traditional. The results of the correlation matrix were significant at the p < 0.05 level, demonstrating that the decrease of rural population, agricultural land, and arable land were directly related to the decline of suspended sediment. High correlation coefficients were found between anthropogenic indicators and sediment parameters, ranging from 0.94 to 0.97.