How most influential ecological and geomorphologic river concepts shaped modern aquatic ecology and restoration

Freshwater ecosystems have been significantly transformed by human impacts on watersheds, resulting in major decreases in the abundance and diversity of fish populations. To address these transformations, increased fish abundance is a common motivator of river restoration projects. Despite the central importance of fish as a provider of numerous ecosystem services (including food, cultural services, and critical ecological roles in river systems, biological processes), influential ecological models of rivers often ignore their role. As a result, restoration too often considers fish as simply a product of other elements of river structure and function. This leads to restoration actions frequently assuming that restoring physical complexity will also result in biological complexity—not necessarily targeting actions directly toward biological processes. Moreover, due to time and budget constraints, restoration is often planned at a spatiotemporal scale that does not yield measurable benefits for the targeted species (e.g., reach scale and over a few seasons). Here, we review the major conceptual models informing our view of freshwater ecosystems and how they shaped our view of habitat restoration, examining if this could be the reason restoration focus the physical habitat aspects, with a rare integration of the biological ones.