Rivers are fundamental landscape components that provide vital ecosystem services, including drinking water supplies, habitat, biodiversity, and attenuation of downstream fluxes of water, sediment, organic carbon, and nutrients. Extensive research has been devoted to quantifying and predicting river characteristics such as stream flow, sediment transport, and channel morphology and stability. However, scientists and society more broadly are often unaware of the long-standing effects of human activities on contemporary river ecosystems, particularly when those activities ceased long ago, and thus, the legacies of humans on rivers have been inadequately acknowledged and addressed.
Legacies, in this context, are defined as persistent changes in natural systems resulting from human activities. Legacies that affect river ecosystems result from human alterations both outside river corridors, such as timber harvesting and urbanization, and within river corridors, including flow regulation, river engineering, and removal of large-wood debris and beaver dams.
Failure to recognize the legacies of historical activities can skew perceptions of river process (the interactions among and movement of materials in a river system) and form (the physical configuration and characteristics of the land and vegetation in a river system) as well as the natural range of variability in river ecosystems, which in turn hampers informed decision-making with respect to river restoration and management efforts. This scenario has played out prominently, for example, with rivers in the Mid-Atlantic Piedmont and Pacific Northwest of the United States.
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