How strong is the evidence – based on macroinvertebrate community responses – that river restoration works?

Secondary production of macroinvertebrates as indicators of success in stream rehabilitation

“…Importantly, however, it did show how rapidly macroinvertebrate secondary production improvements can begin. This latter result provides an important guide to structuring post‐project monitoring, shown by a recent review to be necessary but infrequently implemented (Al‐Zankana et al, 2020). In particular, early regular sampling can detect rapid changes, and should not be discarded in favour of less frequent but longer‐term approaches.…”

“…Understanding the effectiveness of river rehabilitation techniques is critical for directing future rehabilitation projects, planning and design (Roni & Quimby, 2005). The need for monitoring to achieve this has been acknowledged (Al‐Zankana et al, 2020; Roni & Beechie, 2013), but such monitoring and evaluation is still rare (Al‐Zankana et al, 2020; Bernhardt et al, 2005; Kail, Brabec, Poppe, & Januschke, 2015; Palmer et al, 2010; Wolter et al, 2013). Most river rehabilitation schemes fail to assess outcomes and effectiveness (Cowx et al, 2013; Thompson, 2015), or use inadequate statistical designs, or inappropriate biological methods, which hamper rehabilitation ecologists' ability to detect changes (Friberg et al, 2016).…”

“…Most river rehabilitation schemes fail to assess outcomes and effectiveness (Cowx et al, 2013; Thompson, 2015), or use inadequate statistical designs, or inappropriate biological methods, which hamper rehabilitation ecologists' ability to detect changes (Friberg et al, 2016). Despite the increasing number of rehabilitation interventions and an increased social drive to identify effective solutions that have economic benefits (Everard, 2012; Reichert, Langhans, Lienert, & Schuwirth, 2015; Smith, Clifford, & Mant, 2014), evidence for strong and long‐term positive ecological effects of hydromorphological rehabilitation—particularly on macroinvertebrates—is generally limited (Al‐Zankana et al, 2020; Feld et al, 2011; Friberg et al, 2014; Palmer et al, 2010), with few notable exceptions (Kail et al, 2015; Miller et al, 2010). These findings partly reflect the lack of robust scientific assessments of rehabilitation measures (Verdonschot, Kail, McKie, & Verdonschot, 2015).…”

“…There have been many criticisms of river rehabilitation projects for not meeting their goals, or for not being monitored sufficiently well to determine whether their goals were met (Al‐Zankana, Matheson, & Harper, 2020; Barnes, Vaughan, & Ormerod, 2013; Miller, Budy, & Schmidt, 2010). Many hundreds of projects in the USA and EU, designed to rehabilitate natural flow and enhance habitat heterogeneity in streams and rivers, have been monitored to assess their effects on macroinvertebrate biodiversity, evidence for strong and long‐term positive ecological effects of them—particularly on macroinvertebrates—are generally limited (Al‐Zankana et al, 2020; Barnes et al, 2013; Miller et al, 2010). Indeed, biodiversity per se may not be a sufficiently nuanced criterion by which to gauge the ecological recovery or enhancement of rehabilitated streams (Dolph, Eggert, Magner, Ferrington Jr, & Vondracek, 2015).…”

Adding large woody material into a headwater stream has immediate benefits for macroinvertebrate community structure and function

“…An extensive review of the existing literature was conducted, focusing on peer‐reviewed literature and readily available unpublished literature, such as dissertations, theses, and case study reports (Al‐Zankana, Matheson & Harper, 2020). The search was not restricted to particular journals.…”