Assessing and Managing the Impacts of Mixtures of Chemicals on UK Freshwater Biodiversity in a Changing World

We are facing a global biodiversity crisis and freshwater biodiversity is declining more rapidly than either terrestrial or marine biodiversity. One in ten freshwater and wetland species in England are threatened with extinction and two thirds of existing species are in decline. Regulatory data suggest that chemical pollution from wastewater discharges, transport, urban environments, agriculture and mining all contribute to failures against existing quality standards. The Environmental Audit Committee recently summarised the state of water quality as: "rivers in England are in a mess. A 'chemical cocktail' of sewage, agricultural waste, and plastic is polluting the waters of many of the country's rivers". However, these assessments of the impacts of chemicals on UK surface waters, are unlikely to reflect real impacts as they: focus on a small proportion of chemicals in use; take a single compound-single endpoint approach; ignore the combined effects of chemicals, water quality parameters and species interactions; and do not recognise that the sensitivity of ecological communities can vary in space and time. If we are to halt biodiversity loss in UK rivers while continuing to realise the societal benefits of chemicals, we urgently need more effective methods for assessing, predicting and managing the impacts of chemicals both now and in the future.

We aim to deliver and demonstrate a new assessment framework that accounts for the known variability in the physico-chemical and ecological characteristics of a catchment and determines the combined impacts of mixtures of chemicals, bioavailability modifiers and nutrients on the structure and functioning of species assemblages at high spatial resolution. The framework will be developed not only to assess current chemical impacts but also future impacts resulting from changes driven by global megatrends such as climate change, urbanisation and population growth. Using 350 sites in nine Yorkshire river catchments covering different land-uses and pollution pressures, we will develop, test and demonstrate our framework by: 1. prioritising chemicals emitted to UK freshwaters to identify those chemicals in catchments that are driving impacts; 2. characterising current (2002-2022) and future (2061-2080) chemical exposure and general water quality parameter profiles in UK catchments; 3. estimating the effects of chemicals on UK-relevant species under different water quality conditions; 4. predicting the current and future combined effects of chemical mixtures, bioavailability modifiers and nutrients on biodiversity and ecosystem function; and 5. applying the findings to identify interventions to mitigate the impacts of chemicals on biodiversity now and under future climate and catchment change.

The understanding and predictive modelling tools developed during this project will inform the development of better plans for adaptation and mitigation of risks associated with declining water quality now and in the future. By working closely with our partners, who include key representatives from the policy (JNCC), regulatory (HSE), major industry (Unilever, UKWIR, Network Rail) and NGO (National Trust, Rivers Trust) sectors, we will provide policy makers with the knowledge and frameworks to realise a paradigm shift towards chemical risk assessment that will protect biodiversity and key environmental functions in areas where they are vulnerable. Regulators and industry alike will be able to focus future investments and effort on scenarios where harm is most likely/actually occurring. Manufacturers of chemicals will be in a better position to produce chemicals that are beneficial to society but which do not negatively impact the natural environment and the ecosystem services that it provides. Only by taking an integrative and system-wide approach adopted in this project will we be able to deliver the Environment Act's aspiration to "reverse the decline in species abundance by the end of 2030".