Agricultural activities are an important source of pressures on freshwaters, due to nutrient and chemical pollution, water abstraction and physical changes in habitats, including through water storage and land drainage. Agricultural pollutants are transported in water runoff from farmed land and as ~70% of land in England is farmed, this collectively constitutes a significant pollution source. Rainfall can wash a proportion of nitrogen and phosphate from fertilisers off fields into local waterways or cause soluble nutrients to filter into groundwater. Nutrients can fuel unusually high growth rates in microorganisms and plants, which at low levels causes a loss of biodiversity, and at high levels can cause algal blooms that can produce high concentrations of toxins and remove all the oxygen (a process known as eutrophication). This can cause excessive plant growth that can clog waterways. Insecticides, fungicides and herbicides can also be washed into water bodies by rainwater or may enter them directly if spraying close to water and enter groundwater via soil infiltration. Erosion washes topsoil into water bodies, where it causes problems in channels downstream, increasing flood risk, smothering fish breeding grounds and reducing biological diversity in riverbed gravels, as well as carrying large amounts of phosphate and agrichemicals that bond to clay particles. Animal manure and slurry stores on farms are sources of faecal matter with widespread contamination of water courses in the UK.

While agriculture is only responsible for 1% water abstraction in the UK at present, this may increase with climate change impacts on rain fed crops. In England, wetland areas such as fen, marsh, swamp and bog have been lost from lowland floodplains, with 64% converted to arable farming and 85% of rivers in 555 catchments having no associated wetlands. Restoring them may help moderate flood risks, stabilise river flows, improve water quality and provide other environmental benefits. Key measures needed to improve the quality of freshwater ecosystems include: restoring the natural quantity, timing, and variability of water flows and levels; improving water quality; controlling non-native species invasions in freshwater habitats; and restoring the connectivity of freshwater systems.

A POSTnote on this subject will summarise the wide variety of management measures that exist to tackle agricultural pressures on the water environment, as well as set out the challenges of implementing a combined approach that addresses both agricultural practices and consumer demands.

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