measures to preserve or restore a certain environmental quality to rivers. These measures consider, often in an integrated manner, physicochemical, biological, and hydromorphological issues (e.g. the US Clean Water Act, 1972; UK Water Act, 1973; French Water Laws, 1992, 2006; EU Water Framework Directive, 2000; Australian Water Act, 2007). These legislative frameworks have provided a fertile ground for the multiplication of restoration projects, as shown by several reviews conducted around the world (e.g. Bernhardt et al. 2005; Nakamura et al. 2006; Brooks and Lake 2007; Morandi et al. 2017; Szałkiewicz et al. 2018).
River restoration policies, whether at the legislative or technical level, are supported by substantial interdisciplinary research efforts. Scientific work focused on the dynamics of restoration research has shown a major increase in productivity, starting in the 1990s (Shields et al. 2003; Ormerod 2004; Bennett et al. 2011; Smith et al. 2014; Wohl et al. 2015). This increase in scientific research accompanies an increase in the number of projects implemented (Bernhardt et al. 2005) and reflects the strength of science–management links in the field. Applied work in ecology, hydrology, and hydromorphology (Palmer and Bernhardt 2006; Vaughan et al. 2009; Wohl et al. 2015) has been carried out to better understand the functioning of river systems and to assess their responses to restoration actions. As these actions are often innovative, it is difficult to predict their effects, and adaptive approaches based on monitoring are therefore generally preferred (Downs and Kondolf 2002). The current thinking in the natural sciences, notably on the links between hydromorphological structures and processes (Kondolf 2000), or between habitats and biodiversity (Palmer et al. 2010), has been nourished by as much as it has nourished ecological restoration practices (Smith et al. 2014). Bradshaw (2002, p. 7) introduced “restoration as an acid test for ecology” and thus emphasized the links between ecological restoration (practice) and restoration ecology (science). While these special links have long led to the association of river restoration with natural sciences, they have not prevented calls to broaden the spectrum of disciplines involved in restoration approaches (Cairns 1995; Ormerod 2004; Palmer and Bernhardt 2006; Wohl et al. 2015).
1.1.2 An evolution in the positioning of societal issues in debates on river restoration
Societal1 stakes have always structured thinking in the field of restoration. Back in the 1990s, Cairns (1995, p. 9) wrote that “ecological restoration must involve ecosocietal restoration. This is the process of reexamining human society’s relationship with natural systems so that repair and destruction can be balanced and, perhaps, restoration practices ultimately exceed destruction practices.” This thinking is part of a more general movement questioning the relationship between human and nature as it has been encompassed in modern Western thought. This questioning, which has permeated society since the 1970s, is sociocultural, anthropological, and philosophical (Gobster and Hull 2000). It is sometimes championed by natural science researchers who advocate a new ethics of nature (e.g. Jordan 2000; Clewell and Aronson 2013). These ethics are based on the recognition of nature as having an intrinsic value as much as they are based on observations of the degradation of this value by human societies. They are formed at the point of convergence between conservationist movements and scientific advances in the natural sciences. Human activities are characterized by the natural sciences, often in terms of pressures; it is a time of guilt. The ultimate goal of restoration projects is to return rivers to the good (pristine) state they were in before degradation by human societies.
Very quickly, the original idea of the river’s return to a past state, what some authors have called the myth of the return to Eden (e.g. Dufour and Piégay 2009), was strongly criticized for reasons mainly related to scientific uncertainties and technical feasibility, but also to ethical positions. Restoration is certainly based on a new attitude toward rivers, but it must also deal with reality, including the social and economic reality of its implementation. The conceptualization of the Anthropocene is part of this evolution (Crutzen and Stoermer 2000). Studies highlight the importance of both biophysical and societal contexts in the implementation of actions. It is a time for pragmatism; leaders of restoration projects seek to do the best that they can ecologically within a given context. This realization is accompanied by a discussion of the concept of restoration and an evolution of its definitions (see Box 1.1). As Wohl et al. (2005, p. 2) point out: “because both technical and social constraints often preclude ‘full’ restoration of ecosystem structure and function, rehabilitation is sometimes distinguished from restoration.” The concept of rehabilitation often carries the idea of a relaxation of the restoration objectives and a redefinition of the references used to define these objectives (Dufour and Piégay 2009). What is being restored? But above all, why is it being restored? Restoration, which until now was guided by the intrinsic value of the river, embodied by concepts such as ecological integrity, is opening up to more instrumental visions.
Box 1.1 River restoration: an “essentially contested concept”
The debates, and often polemics (e.g. Normile 2010), concerning what is and is not river restoration are numerous (e.g. Roni and Beechie 2013; Wohl et al. 2015). These debates on the definition of restoration have been fueled by the proliferation of concepts that are now widely used in the literature, such as “rehabilitation,” “renaturation,” “revitalization,” “enhancement,” and “improvement.” If there is one certainty emerging from these debates, it is that attempts to provide an unequivocal and definitive answer to the question “What is restoration?” are doomed to failure. There has never been a consensus on definitions, and there certainly never will be. The concepts of restoration, rehabilitation, or renaturation are “essentially contested concepts” (Gallie 1956, p. 169), that is to say, “concepts the proper use of which inevitably involves endless disputes about their proper uses on the part of their users.” The interest in the debates lies not in their conclusions but in the debates themselves and the ideas that emerge from them.
The definitions that have been used as references in the field of restoration show the evolution of these debates. Initially conceived as techniques, the definitions raised ethical questions as early as the 1990s and particularly questioned the hermetic separation between human and nature (Table 1.1). According to Westling et al. (2014, p. 2614), “This dichotomy is challenged, both by alternative theoretical frameworks arguing for the relevance of natural‐cultural hybrid models for restoration, and by pragmatic perspectives that take restoration to be the balancing of ecological and human goals through rehabilitating or enhancing landscapes, rather than seeking return to a redundant, historical reference state.” The efforts of scientists and managers are now aimed at clarifying the definitions of references and concepts such as “Lietbild” (Kern 1992) or “guiding image” (Palmer et al. 2005) to clarify the restoration objectives (Weber et al. 2018). In the definition of these objectives, the tension between an eco‐centric approach that emphasizes the intrinsic value of the river and an anthropocentric approach carrying more utilitarian arguments is notable (Dufour and Piégay 2009).
Table 1.1 Definitions of river restoration selected from the international scientific literature illustrating the place of societal issues in conceptual debates.
| NRC 1992, p. 18 | “Restoration is defined as the return of an ecosystem to a close approximation of its condition prior to disturbance. In restoration, ecological damage to the resource is repaired. Both the structure and the functions of the ecosystem are recreated.” |
| Stanford et al. 1996, p. 393 |
“The goal of river restoration should be to minimize human‐mediated constraints, thereby allowing natural re‐expression of productive capacity. In some, if not most, intensely regulated rivers, human‐mediated constraints may have progressed to the point that full re‐expression of capacity is neither desired nor possible. Nonetheless, the implication
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