Sediment Response to Deforestation in the Amazon River Basin

Abstract

The Amazon River Basin is the largest river basin in the world (6,300,000 km2) and serves as a home to approximately 26 million people across the South American continent. Renowned for its biodiversity, the Amazon River Basin is home almost 50,000 vascular plant species, 2,000 species of freshwater fishes, and was once one of the Earth's largest carbon sinks. Despite its anthropogenic and ecological importance, the Amazon experiences thousands of kilometers of deforestation annually with recent rates increasing to levels unseen since the late 2000s. These increased rates of deforestation within the basin have led to changes in sediment concentration within its river systems, affecting both the ecological balance and freshwater availability within the system. Furthermore, sediment plays an important role in river channel morphology and landscape development, effectively influencing the future topography of the basin. Therefore, it is important to closely examine the relationship between deforestation and suspended sediment in order to characterize the extent of influence anthropogenic activities, such as deforestation, have on rivers. In this study, I analyze the impact of deforestation from 2001 to 2020 on suspended sediment throughout the Amazon River Basin. These impacts are studied by quantifying the spatiotemporal relationships between observed suspended sediment and changes in land cover over time. In the southeast region of the Amazon, where deforestation rates are high, I observed strong correlations between deforestation and total suspended solids concentration. Basin wide, I determined that 26% of the temporal variability in sediment is attributed to deforestation. Sub-basins subject to large amounts of deforestation during the study period were shown to have sediment spatial dynamics more heavily influenced by deforestation than their more pristine counterparts. Further, at local scales, large amounts of deforestation were observed to be associated with increases in total suspended solids. The results of these analyses reveal that large scale deforestation of the Amazon during the 2001-2020 period may have led to significant changes in sediment dynamics predominantly in the eastern portion of the basin. These findings suggest severe implications for future sediment dynamics across the Amazon if deforestation is to further expand into the basin.