Freshwater ecosystems, including rivers are amongst the most threatened in the world. Extensive and pervasive human activity is associated with severe ecological degradation and the loss of biodiversity (i.e. the variability among living organisms, including diversity within and between species and of ecosystems (CBD, 1997)) across dynamic natural environments. River systems, from catchment to reach scales, have been substantially modified and fragmented, which has led to alteration of flow, flooding, and sediment regimes, eutrophication, species richness, and deteriorated water quality. To counteract such adverse impacts, river restoration has increased in popularity since the 1990s with a focus on conserving and enhancing ecosystem services, and remediating ecological degradation. The value and importance of freshwater ecosystems both ecologically and in the context of human social and economic activity is internationally recognized; this is evident through the United Nations Sustainable Development Goals (UN, 2022) and the UN Environment Program, that helps numerous countries to protect, conserve, and restore freshwater ecosystems in order to maintain and enhance ecosystem services for future generations (UNEP, 2022). Billions of dollars are invested into restorative efforts annually, yet the lack of follow-up monitoring, assessment, and evaluation limits what is known of the nature of river restoration in practice. Further, the implications of the Anthropocene – that is, the current geologic epoch where human activities are dominant across natural environments – are poorly understood in the field of river restoration.
This thesis tests the suitability of current restoration methods and frameworks in their application to Anthropocene rivers, and proposes that on-ground river restoration practices may not adequately consider or incorporate the inherent diversity of dynamic fluvial ecosystems. Working to enhance or repair such diversity is a key component of holistic river management, as evident in ‘room to move’ or ‘erodible corridor’ concepts and ‘working with the river’ approaches. Holistic approaches to ecosystem management are central in addressing the fragmented landscape problem; this is characteristic of riverine landscapes, where the implementation of dams, channelization, and homogenization of channel structure and functionality has compromised temporal (e.g. relating to seasonality of flow), lateral, longitudinal, and vertical connectivity. This thesis proposes that current river restoration methods are unlikely to be fully efficacious (referring to the ability or capacity to produce a desired result), effective (the degree to which something is successful in producing a desired result), or efficient (cost and resource-effective) in the Anthropocene, which may compromise ecosystem services provided by rivers.
The aim of this thesis is to determine the nature, and subsequently advance the science and practice of river restoration. This thesis comprises two main research foci. Firstly, a test of river restoration theory to practice is presented through a systematic review in regional NSW Australia. This is informed by current river restoration literature that expresses the multitude of ways in which river restoration has progressed away from command-andcontrol activities towards holistic approaches that consider inherent diversity of river functions and processes. Secondly, grounded in river science theory and concepts of what rivers should be, a framework for restoring and repairing rivers in the Anthropocene is presented. This consists of three building blocks that consider principles of resilience thinking, landscape ecology, and river science.
The findings of this thesis suggest that on-ground practices often do not work with the river, and that current river restoration methods generally do not consider the irreversibility of state-change frequently evident. This highlights the need to reframe river restoration in the Anthropocene, to ensure anthropogenic activities and impacts are increasingly at the forefront of fluvial ecosystem rehabilitation.