Socio-ecological complexity and the restoration of river ecosystems

Understanding socio-ecological characteristics associated with rivers and their catchments, and using that understanding to effectively manage and restore river ecosystems, is an increasingly complex challenge. While great strides have been made in the last half century in understanding rivers as ecological systems, human exploitation of river water and riparian zones have frustrated river management to the point that many native species are imperiled or have become extinct, invasive species are rampant, water and sediment quality are in significant decline, environmental flows are neglected, and economic pressures are placing unprecedented demands on remaining resources. At the same time, there are societal expectations that river resources be restored or rehabilitated to functional states, even while climate change, population growth, flow diversion, and the proliferation of chemicals impose additional burdens in ways that are not adequately understood. Therein lies one of the great challenges of this century. Can river systems be realistically restored or rehabilitated and, if so, what are the approaches and scales that have a chance of being successful? The 2013 E. Baldi lecture addresses these questions by examining 2 examples of river restoration: identifying socio-ecological attributes from those examples that have been successful as well as aspects needing improvement, and presenting principles for improving river restoration in highly complex situations. The principles are designed to enhance resilience and promote adaptive capacity within social–ecological systems—systems that continue to evolve