Increased water pollution from farms will become common under climate change

Increased water pollution from farms will become common under climate change - Rothamsted Research

Very wet winter made polluted river more than twenty times worse

A study of river water quality during one of the UK’s wettest ever winters shows a massive increase in agricultural pollution occurred, giving a glimpse of what is to come under future climate change.

Pollutants washing from farmland within the upper catchment of Devon’s River Taw increased dramatically during the winter of 2019/20, with the amount of soil washed off arable fields – and the associated environmental clean-up costs - showing a twenty-fold increase on average.

Large pulses of such sediment pollution harm both aquatic wildlife and drinking water quality, and the study’s climate modelling predicts the weather pattern responsible will be more common in the future.

The report by Rothamsted Research also shows levels of nitrate, another major aquatic pollutant arising from fertiliser use, increased by four times during the wet winter from recently converted arable land.

Meanwhile, the sediment lost from grazed grassland areas roughly doubled, with nitrate runoff increasing by about half.

Hydrologist Professor Adie Collins, who leads Rothamsted’s research in this area said: “These changes in autumn and winter rainfall are elevating runoff and the water pollution problems arising from modern farming. Sadly, current on-farm mitigation strategies, including those subsidised by agri-environment schemes, aren’t working very well.”

February 2020 was the wettest February on record for the UK, with the meteorological winter - December, January, February - ranked as the 5th wettest on record since 1862.

The researchers produced climate predictions for their study site, which suggest this sort of weather pattern will become more common in the future - with the most extreme rain days occurring even more often than they did in February 2020.

Alongside the impact on wildlife, water pollutant emissions affect the provision of valuable ‘ecosystem services’ to humans, said Professor Collins, and these impacts were assessed using the concept of ‘environmental damage’ costs.