Professional and citizen science to monitor and improve the physical habitat quality of rivers

Physical habitat and hydromorphological processes are fundamental to river ecosystem functioning and essential for restoring rivers subjected to multiple stressors. Extensive loss and damage to river and floodplain habitats caused by centuries of industrial, agricultural and urban development are preventing many rivers from achieving good ecological status even in places where water quality has improved. Restoration of river health and long-term resilience cannot be achieved without the foundation of good hydromorphological condition. Despite this, assessment of river health continues to be dominated by water quality monitoring. This imbalance has been exacerbated by increased public anger about serious pollution incidents, prompting an upsurge in environmentalist democracy, often led by activists participating as ‘citizen scientists’ (CS) at a local scale. Compared to chemical and biological water quality monitoring, assessment of physical habitat and hydromorphological quality is difficult and complex and the legal basis for monitoring is weak, resulting in low public awareness. Moreover, hydromorphology is not widely promoted in education, and professional expertise is scarce. We consider how CS volunteers might contribute to survey and assessment of physical habitat, proposing credibility and fitness-for-purpose tests for this activity. Reliable field data collection and valid interpretation are dependent on purpose and end use, deployed through appropriate survey design, sampling strategy, training and quality control protocols. Flexibility in the level of technical competence required for different types of field survey, allows carefully focused CS participation, although substantial professional input is required to ensure scientific and legal credibility. We recognise the invaluable advocacy role that CS volunteers can provide in raising public awareness and habitat restoration work at local level. A technical forum to address methodological validity, harmonisation of sampling effort, compatibility of data platforms and uptake of results would provide scientific credibility and build trust between professional river scientists and volunteers necessary for the effective deployment and uptake of CS surveys. Managed interaction would help to maximise efforts to restore rivers to full health in the context of building resilience for humans and biota under future rapid environmental change.