A key concern regarding current and future climate change is the possibility of sustained droughts that can have profound impacts on societies. As such, multiple paleoclimatic proxies are needed to identify megadroughts, the synoptic climatology responsible for these droughts, and their impacts on past and future societies. In the hyperarid Atacama Desert of northern Chile, many streams are characterized by perennial flow and support dense in-stream wetlands. These streams possess sequences of wetland deposits as fluvial terraces that record past changes in the water table. We mapped and radiocarbon dated a well-preserved sequence of in-stream wetland deposits along a 4.3-km reach of the Río San Salvador in the Calama basin to determine the relationship between regional climate change and the incision of in-stream wetlands. The Río San Salvador supported dense wetlands from 11.1 to 9.8, 6.4 to 3.5, 2.8 to 1.3, and 1.0 to 0.5 ka and incised at the end of each of these intervals. Comparison with other in-stream wetland sequences in the Atacama Desert, and with regional paleoclimatic archives, indicates that in-stream wetlands responded similarly to climatic changes by incising during periods of extended drought at ~9.8, 3.5, 1.3, and 0.5 ka.

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Streams in the Midwest of the United States have experienced major changes in their watersheds since European settlement that have altered sediment loads, runoff, nutrient concentrations, and the abundance of woody debris. Moreover, the near extirpation of keystone species such as beaver, and the construction of dams and impoundments (e.g., milldams, causeways, reservoirs, small ponds, etc.), have had impacts on the entrainment of sediments, the connectivity between tributaries, main channels, and floodplains, and channel form. As stream restoration efforts increase, how do we restore streams to their ‘natural’ state? Can streams restored to a pre–European settlement condition maintain equilibrium under current land use? Here we examine the impact of post-European settlement changes to a small (432 km2) watershed in southwestern Ohio that is largely representative of rural watersheds in the Midwest. We examine the impact of nineteenth-century milldams, report the results of a 21-year study of nutrient and sediment concentrations in the upper portion of the watershed during a shift from conventional to conservation tillage, and assess the potential impact of the return of beavers on stream sediment and nutrient concentrations. Our objective is to understand how streams have been impacted by humans over the past 250 years, and to identify strategies for ‘restoring’ streams in the Midwest.

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