the authors, the crossing of disciplinary viewpoints is an essential approach to address any problem in an integrated manner, and to take into account its various facets. Other publications put scientific knowledge into perspective by comparing it with other more vernacular forms of knowledge (e.g. Woelfle‐Erskine 2017; Hong and Chun 2018). They contribute to relativizing the weight of scientific knowledge in the decision‐making process and make the scientist a stakeholder among others (Yun 2014). These approaches therefore reflect on processes for engaging local communities and citizens at large in decision‐making processes (e.g. Heldt et al. 2016; Fox et al. 2017; Edwards et al. 2018). To this end, publications consider and evaluate the merits of alternative approaches for the production of knowledge in the field of river restoration. Pahl‐Wostl (2006) insists, for example, on the principle of co‐construction of knowledge to promote social learning in the field of river restoration. Restoration projects involving participatory science (e.g. Edwards et al. 2018) or collaborative research (e.g. Fox et al. 2017) are, however, rare. Fox et al. (2017, p. 532) showed that “spaces for the inclusion of new meanings, processes, and outcomes in restoration” were created through collaborations between researchers and indigenous communities. They have contributed to the recognition that the standards of indigenous communities are on a par with those of Western countries. According to the authors, however, this recognition is only one step on the long road to rebalancing power relationships in river restoration governance processes.
1.4.3 Economic evaluation of river restoration
Economic analyses were among the first societal approaches developed in the field of river restoration (e.g. Barendregt et al. 1992; Loomis 1996; Turner and Boyer 1997) (Figure 1.11). Several works are now widely referenced and utilized in the scientific community (Loomis et al. 2000; Chen et al. 2017; Acuña et al. 2013; Vermaat et al. 2016; Bliem et al. 2012; Gerner et al. 2018). Economic approaches focus primarily on producing an assessment of river restoration policies; however, in contrast to budgetary approaches to public policy evaluation, which are placed from the point of view of funders and primarily consider the financial costs of projects, they adopt a more socioeconomic perspective for this evaluation (Brouwer and Sheremet 2017). Thus, the majority of economic publications integrate discussions on social practices and environmental perceptions (Table 1.4). According to Brouwer and Sheremet (2017, p. 1), the economic value of a river restoration project is defined as “the calculation of all costs and benefits, including (second‐order) indirect effects on sectors and (non‐priced) environmental effects, often referred to as the broader social costs and benefits.”
Figure 1.11 A lexicon specific to international scientific publications on the economic stakes in river restoration
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1.4.3.1 Contributions focused on the evaluation of benefits of river restoration
The financial amounts committed to river restoration are an important issue, highlighted by several reviews on river restoration (e.g. Bernhardt et al. 2005; Szałkiewicz et al. 2018). Some economic publications are more focused on project costs alone. Cost reduction is very often the objective of these studies, which take note of the strong budgetary constraints imposed on the implementation of restoration actions. This search for cost optimization leads some authors to question and prioritize the restoration techniques that are adopted in projects (e.g. Hill et al. 2011; Kristensen et al. 2012; Carah et al. 2014). Other authors look at costs from a different perspective, assessing costs as losses to the stakeholders in the restoration. At the heart of these studies is the value of the assets that certain stakeholders must give up if the restoration project is to be carried out; these are opportunity costs. For example, Gómez et al. (2014) consider the opportunity costs associated with the reduced power generation resulting from the implementation of flushing floods which are known to restore basic environmental functions in highly engineered rivers. In particular, they demonstrate that this cost is lower than the willingness to pay for such restoration measures. Losses are also sometimes considered in terms of the compensation to be paid to the stakeholders affected by the restoration project (e.g. Cheng et al. 2019). Such cost‐only approaches are not dominant in the literature.
The vast majority of the literature with an economic approach to river restoration compares costs against benefits or focuses on assessing benefits alone. In the cost–benefit analyses, it is above all the evaluation of benefits that is at the heart of the research effort. The costs are considered as fixed data that are not very open to discussion. Behind this interest in the benefits, there exists a form of engagement of the scientific community that is in favor of river restoration policies. By making visible the benefits induced by the projects and highlighting their effectiveness from the point of view of public investment, these publications help to justify and promote river restoration to decision‐makers and the general public. This focus on benefits can also be explained by the methodological challenges faced by researchers. While it is indeed relatively easy to access project cost data – at least for technical implementation – the measurement of benefits is more challenging (Brouwer and Sheremet 2017). This is all the more true because environmental benefits are most often of a nonmarket value that is difficult to measure. To determine this value, which some authors describe as a “shadow price” (e.g. Grossmann 2012; Becker et al. 2014), economics relies on a substantial methodological arsenal (see Box 1.4).
1.4.3.2 What river restoration benefits are we talking about? The ecosystem services approach
River restoration is likely to produce multiple benefits, whether ecological (e.g. restoration of certain ecological functions), economic (e.g. creation of a market and thus of companies or consulting firms specializing in river restoration), or social (e.g. development of recreational opportunities associated with rivers). To capture these benefits, economic approaches to river restoration are essentially based on the concept of ecosystem services. They are thus part of an anthropocentric paradigm of interactions between societies and rivers. Ecosystem services are defined as the benefits that society derives from ecosystems and that therefore contribute to human well‐being (Costanza et al. 1997; Daily 1997; MEA 2005)2. Ecological structures and processes perform ecological functions that are themselves sources of services for humans. However, these services are only regarded as benefits when society attributes a value to them (Haines‐Young and Potschin 2010). Quantification of this value is an issue mobilizing a significant proportion of the economic science community working on restoration issues.
Box 1.4 Economic methods: assessing the benefits of river restoration
The evaluation of the benefits produced by river restoration in relation to the costs it generates is at the center of many economic studies. The bibliographical work makes it possible to distinguish two main approaches in the way this evaluation is conducted.
1 The first is cost‐effectiveness analysis. Several publications measure the benefits of restoration according to ecological (e.g. Barendregt et al. 1992; Langhans et al. 2014) or socio‐ecological (e.g. Golet et al. 2006; Jia et al. 2010; Kendy et al. 2018) indicators, which they compare against monetary project costs.
2 The second and more common approach compares costs to economic benefits. While the measurement of costs is not described in the literature as posing any particular problems, the measurement of benefits raises important methodological issues. The benefits of a project are multifaceted, and in practice correspond to very different units of measurement (e.g. the