Sediment Response to Deforestation in the Amazon River Basin

The Amazon River Basin is the largest river system in the world, accounting for one-fifth of global freshwater discharge and supplying 40% of the Atlantic Ocean's sediment flux. Though the Amazon is most often recognized for its rich biological diversity, it also performs a suite of ecosystem functions such as river flow regulation, local climate modulation, and carbon sequestration. Despite its 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 not only the ecological balance within the system but also the availability of water to those dependent on river flows. 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, we analyze the impact of deforestation from 2001 to 2020 on suspended sediment throughout the Amazon River Basin. These effects are studied by quantifying the spatiotemporal relationships between observed suspended sediment (at gage sites and using a basin wide remote sensing product) and changes in land cover over time. We also observe that 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, we see that sediment may have a delayed response to deforestation that is tied to the amount of forest loss occurring. 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.