Testing the efficacy of river restoration across multiple levels of biological organisation

Abstract

As we start to count the cost of unprecedented biodiversity loss in terms of impaired provisional, supporting and cultural ecosystem goods and services, so to are we increasingly implementing measures to halt and reverse these impacts. A major focus of these efforts has been the restoration river habitats, which rank among the most degraded globally. However, while river restoration has become a global enterprise, biomonitoring to test the ecological effectiveness of these activities remains exceptional and even then typically lacking the rigour necessary for detecting and tracking ecological responses across space and time. Here I use standardised and quantitative biomonitoring techniques to measure the ecological response to replicated, experimental, reach-scale large wood installations in heavily modified calcareous system. In Chapters 3-5, I used biannual biomonitoring to investigate the response of a target fish species and the wider fish assemblage to restoration and found strong, rapid responses in the target species’ predators (Chapter 3). In Chapter 4, I build food webs revealing changes to the food web structure that indicate enhanced energy transfer between predators and prey following restoration. In Chapter 5 I investigate the effect of restoration on ecosystem functioning, by comparing leaf-litter breakdown rates and colonisation in restored and unrestored reaches. In Chapter 6, I discuss how engaging river users as citizen scientists could advance the ecological success of their interventions and restoration science. The findings presented here highlight the importance of robust biomonitoring methods for revealing, measuring and characterising the response of ecological communities to habitat interventions. Repairing degraded ecosystems is among the most necessary and exciting challenges we have undertaken as a species, and only by advancing our understanding the factors that influence restoration success and failure will we be able to advance the practice of restoration towards an ever more efficient and ecologically effective management practice.