Strategies for Restoring River Ecosystems: Sources of Variability and Uncertainty in Natural and Managed Systems. Robert C. Wissmar and Peter A. Bisson, eds. American Fisheries Society, Bethesda, MD, 2003. 283 pp., illus. $69.00 (ISBN 1888569468 paper).
In a special issue of BioScience in 1995 entitled “Ecology of Large Rivers,” Johnson and colleagues (1995) pointed out in their introductory article that a number of useful concepts had been developed to understand the interactions between physical and biological factors in large river systems. They also highlighted the fact that these concepts failed to recognize the importance of nested scales of interactions, both spatial and temporal, between large-scale processes (such as climate change and tectonic factors) and smaller-scale processes (such as intraspecies and river flow–species interactions). The authors additionally stated that “better methods and tools are needed…to predict a river's physical and biological characteristics along its length.” The authors were absolutely right on both counts, and that issue of BioScience was for me an important landmark in the promotion of more holistic and connected thinking about what we might aspire to achieve in river restoration and how we could approach it.
Of course, it is now clear that predicting physical and biological characteristics along a river's length is not just difficult—it is, in absolute terms, impossible. And yet predictability is exactly what river restorers would like. The reason predictability will remain the elusive Holy Grail is the subject of this very timely volume edited by Robert Wissmar and Peter Bisson. In Strategies for Restoring River Ecosystems, a series of well-edited chapters run the gamut, from sources of variability in climate change and all its knock-on effects into hydrological and geomorphological patterns, through sources of variability in riparian and aquatic ecosystems, to uncertainties in watershed assessment techniques and watershed decisionmaking approaches. By the end of the book it becomes clear that variability, uncertainty, and unpredictabilty are in fact the hallmarks of river systems and, by extension, of any river restoration initiative.
The book is divided into two sections: The first deals with sources of variability in river ecosystems and the second with uncertainty in developing restoration strategies. The stated aims of the editors were to understand these two areas in order to design robust and more predictable restoration projects and outcomes.
I found chapter 2 on sources of climate variability in river ecosystems (by Edmonds et al.) of great interest. It contains well-judged levels of information from across the huge bodies of knowledge about natural and human drivers of global-scale climate variability, streamflow patterns, and the implications for river restoration. It emphasizes the importance of understanding river flows over short and long time scales, of renaturalizing flows, and of reconnecting river channels and floodplains to ameliorate changes caused by climate variability. I would have liked more discussion on how returning natural variability to river systems would ameliorate the effects of climate change on river systems, because this is a crucial argument in river restoration.
This chapter also points out that assessing climate change impacts at the local scale requires “downscaling” from global climate system models to finer resolutions (such as tributary watersheds), a process that at present has low confidence levels. On the other hand, also difficult is “upscaling” from the reasonably predictable river flow–species interactions in riparian ecosystems that are used to excellent effect in designing planned releases for restoring regeneration in riparian plant communities (e.g., Rood et al. 2003) to predictions of the extent, connectivity, and distribution of riparian ecosystems necessary to maintain viable metapopulations.
These are among the themes picked up in chapter 5 by Wissmar and colleagues, and they mirror parallel ideas in chapter 3, by Montgomery and Bolton, concerning the difficulties of predicting geomorphological change at different hierarchical levels of landscape study. It becomes clear that the range of likely responses to change at each spatial and temporal scale is much more predictable than the exact location at which those responses might manifest themselves. Being able to predict the type of response, but not its location, is not ideal for river restoration initiatives that are confined to one site and are therefore not systemic.
In chapter 4, Hauer and colleagues criticize local-scale restoration approaches exactly because such approaches do not take into account the linkages at nested spatial and temporal scales that need to be addressed in restoration methods. This chapter goes on to provide a useful account of sources of natural and human variation at a landscape scale, covering a wide range of natural processes.
A final chapter in the first half of the book covers sources of variability in aquatic ecosystems (chapter 6, by Bilby et al.). There is an emphasis here, as in chapter 5, on the integral part that natural disturbance processes play in the functioning of aquatic and riparian ecosystems. Both chapters include discussion of “recovery” and the resilience of ecosystems to natural (and often considerable) variations in, for example, river flows, sediment loads, and channel mobility. The message is clear: Restoration efforts must return variability to river systems if a diverse and mobile mosaic of habitats is to be returned to their aquatic and terrestrial components.
In the second half of the book is a particularly enjoyable chapter (chapter 9) by Anderson and colleagues on different decisionmaking approaches to watershed restoration. The authors appear to include a psychologist, a mathematician, and two ecologists, making for a provocative discussion of the social contexts in which decisions are made and the advantages and disadvantages of different decisionmaking approaches. Here, as in chapter 7 (Reisenbichler et al.) on genetic concepts and uncertainties in storing fish populations and in chapter 10, which is a specific case study about the Columbia River Basin, the recovery of fish populations is a strong driver for river and watershed restoration.
The emphasis on watershed restoration rather than local-scale restoration is the subject of chapter 8 (Pess et al.), but the authors also explain why local-scale initiatives often prevail over landscape-scale approaches. It describes the difficulties of dealing with land ownership, legal and funding issues, socioeconomic objectives, and regulatory obligations, among others, and roots the reader firmly in the realities of river and watershed restoration.
The final chapter, written by the editors, does a good job of summarizing many of the main themes of the book through the use of some useful diagrams. Appreciating variability in river systems is a vital precursor to being realistic in our expectations of the range of possible restoration outcomes. Far from being daunted by the realization that we cannot easily predict those outcomes, we should perhaps open our minds to accept their endless and changing variety.
If the book had too much information about fisheries for my personal interest, this can be forgiven: It was published by the American Fisheries Society. What I found disappointing was the complete lack of comparisons with sites outside North America. Nonetheless, the editors should take credit for a thought-provoking volume that greatly adds to the sophistication of our thinking on river restoration.
