Restoration of Freshwaters: Principles and Practice

Abstract

Freshwater ecosystems are in major decline at the global scale and there is an urgent need for successful restoration projects. Although freshwater restoration is a relatively new science, it is at the point where important principles and approaches that underlie success can be broadly established. Covering the full spectrum of freshwater habitats, including rivers, lakes, ponds, and various wetland types, this chapter sets out and discusses six key restoration principles concerned with project targets, diagnosing and tackling underlying and restraining influences, natural recovery and landscape-scale processes, as well as monitoring and working with stakeholders.

Will they be back? A framework to guide rare macrophyte conservation decisions in lakes

“…In line with other studies, we view natural dispersal and recruitment from seed banks to be the preferred conservation options for restoring lost macrophyte populations where conditions allow, an approach that has been described as “passive” revegetation (De Steven et al 2006). It not only offers a more cost‐effective option than “active” approaches, such as reintroduction via planting and seeding, but is also more closely aligned with the good restoration practice of adopting nature‐led approaches (Shuwen et al 2001; Sayer et al 2019). A major advantage of the passive approach is that it directs conservation effort at improving water quality and habitat conditions and, potentially, where appropriate, connectivity to other sites.…”

“…The likelihood of a macrophyte species returning to a lake once it has been lost is contingent on a multitude of factors including suitability of conditions, dispersal capabilities, and opportunities via hydrological connectivity (Salgado et al 2022), wind or birds (Green et al 2002; Soons et al 2008), seed production and the viability of seed banks (Bakker et al 2013; Alderton et al 2017), and proximity to source populations. The questions around whether a species can return, and what restoration strategies are appropriate, are important not only for aquatic systems but also for restoration ecology more widely (Sayer et al 2019). There is much debate across wetland habitats concerning whether sites under restoration should be allowed to seed naturally via dispersal and remnant seed banks or whether plants should be actively introduced (Rodrigo 2021; Fenu et al 2023).…”

The challenge of restoring tropical freshwater ecosystems

“…Lakes are being neutralized, the input of nutrients is being reduced or trapped, fish assemblages are being manipulated, macrophytes are being withdrawn or biologically controlled, whole wetlands are being rebuilt, watercourses are being renaturalized, and margins are being revegetated. After twenty years, although still recently occurring (Sayer et al, 2019), ecological restoration remains a great challenge (Frid & Clark, 1999) but has produced knowledge and methods and resulted in interventions. Some of these efforts have had good results, but others did not.…”

Borrowing from the palaeolimnologists toolkit; the use of lake sediment cores in diagnosing the causes of freshwater species decline

“…Globally, the average abundance of freshwater species has declined by 83% since 1970, far outnumbering those in terrestrial and marine systems (WWF, 2020). Conservation action undertaken to conserve threatened and diminishing populations relies upon diagnosis of the drivers of decline, and identification of appropriate restoration strategies (Caughley, 1994;Sayer et al, 2016b). Conventionally, approaches used to diagnose species decline have focused on spatial associations between species distributions and environmental variables that are considered important (Peery et al, 2004).…”