River Rehabilitation in the Anthropocene

The Anthropocene is proposed as the current geologic epoch wherein humans are the dominant driver of global ecosystem states and functions. There are few large river ecosystems that are not affected by human actions. Large river ecosystems are subject to many, often interacting, anthropogenic stressors including channelization, dam construction, hydrological modification, land-use change, pollutants, species invasion, and urbanization. These stressors can result in changes to the physical structure, biodiversity, food webs, and biotic population demographics of these important freshwater ecosystems. However, rivers are also naturally dynamic ecosystems. Separating the effects of natural and human-induced drivers of change is often difficult in river ecosystems. Understanding the drivers of change is important for river rehabilitation and there are few river models (e.g., The River Ecosystem Synthesis, The River Wave Concept) that focus on rivers in the Anthropocene. The Serial Discontinuity Concept is the only river model that directly addresses the effect of humans on river structures and functions.

Resilience thinking suggests that Anthropocene Rivers are structurally and functionally different from their ‘natural’ cousins and cannot go back to their previous state; they are permanently different. Consequently, contemporary river management practices, such as the determination of environmental flows, levee removal, and the reintroduction of large wood to increase habitat availability, may not be well suited to these novel ecosystems. Relationships between humans and river ecosystems have also changed over time. The traditional command-and-control river management practices are being challenged by the recognition that rivers are part of social-ecological systems. These reflections have important implications for not only the management of riverine landscapes but also how to model these landscapes, whether empirically or conceptually.

This Research Topic invites contributions that address the following questions:

• Can Anthropocene Rivers be rehabilitated to conserve or enhance their structure and function, thus regaining some semblance of their former state?
• Are there regime shifts that can be used to identify Anthropocene Rivers? Can we identify important early warning indicators of Anthropocene Rivers?
• What have we learned from attempts to rehabilitate Anthropocene Rivers and how transferable are these lessons among regions?
• Can we model these novel landscapes, whether empirically or conceptually?
• What are desirable management options for rivers as social-ecological systems? How and who decides what management options are appropriate for rivers as novel social-ecological systems?
• What are the current research and management challenges we face in rehabilitating river ecosystems?

The collection of manuscripts in this Research Topic will explore these challenges and questions. Case studies from different geographic regions and ecosystem perspectives present alternative experiences of rehabilitating Anthropocene Rivers. Manuscripts will explore and unpack the various biophysical, economic, political, and social framings of these experiences, and identify priorities for further research and management.