Professor Penny J Johnes

BSc, D.Phil (Oxon.)

  • BS8 1SS

    United Kingdom

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Personal profile

Research interests

Penny is an environmental scientist by background who has worked on the biogeochemistry of aquatic systems, and the impacts of food production and environmental change on the quality of inland and coastal waters for the past 30 years. She has provided advice to a range of UK Government and international agencies on the nature and scale of nutrient enrichment in waters, the consequences of this enrichment for ecosystem health, and the most effective strategies for the control of nutrient flux from land basd sources to waters.  She is currently a member of the UNECE Task Force for Reactive Nitrogen and its Expert Panel on Nitrogen Budgets, is a member of the IAHS International Commission on Water Quality, sits on the Natural England Science Advisory Committee, Wessex Water Catchment Panel, Defra Biodiversity Targets Advisory Group, Defra Nutrient Management Expert Group, and is Chair of the Defra Water Expert Advisory Group.  

Penny has particular interests in the role of dissolved organic matter as a driver of biodiversity loss in freshwater ecosystems, the potential to develop holistic management strategies which tackle multiple stressors in freshwaters and their catchments, and in ensuring that environmental management policy is underpinned by robust science evidence. She works with researchers across a range of disciplines to meet these challenges, from chemical to biological, environmental, earth, agricultural, social economic and political sciences. 

Her research to date has highlighted the quantitative importance of organic and particulate nitrogen and phosphorus fractions in the total nutrient load transported to and within water bodies; the importance of short-term, extreme flow conditions in controlling the nutrient source/sink function in soils, wetlands and freshwaters; and the necessity when upscaling findings from local to national scale, of defining quasi-homogenous geoclimatic units exerting broadly similar controls on nutrient flux from land to water, as the base unit for modelling.  This research has been critical in helping us to better understand the sources of pollutants within the landscape, the pathways by which material moves from land to stream under differing environmental conditions, and the rates at which this material is cycled, transported and transformed instream. 

Penny's ongoing research includes work characterising the signature of dissolved organic matter (DOM) flux in freshwater systems in relation to nutrient enrichment and climatic controls, funded under a NERC Large Grant (the DOMAINE programme), and a major programme funded by the UK Department of Environment, Food and Rural Affairs, and Environment Agency established to test the hypothesis that it is possible to reduce cost-effectively the impact of agricultural diffuse water pollution on ecological function while maintaining sustainable food production through the implementation of multiple on-farm mitigation measures (the Demonstration Test Catchments Programme).  These programmes capitalise on recent novel analytical and in situ monitoring technologies to elucidate the fine scale variability in nutrient flux behaviours and source character in catchments, and the ways in which the hydrochemical signature of nutrient flux from catchments, defined at high resolution, may be used to diagnose the stresses on that system and their likely responses to proposed on-farm mitigation efforts.

Structured keywords and research groupings

  • Cabot Institute Water Research
  • Cabot Institute Food Security Research
  • Cabot Institute Environmental Change Research


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