The Effects Of Pesticide Use On Watercourses

One of the biggest threats to waterways around the UK is agricultural waste and the use of pesticides and fertilisers, which are increasingly making their way into the natural environment and having a big impact on water quality, wildlife habitats and local biodiversity.

Currently, just 14 per cent of rivers in England meet the standards required for good ecological status, with the poor health of many watercourses now having a significant impact on nature, leading to the decline and even near-extinction of many species.

The use of pesticides in agriculture can lead to contamination of surface water and groundwater sources alike, with the potential to cause harm to the environment if concentrations surpass critical thresholds.

Pesticides are toxic chemicals that have been designed to be deliberately released into the natural environment in order to kill specific pests but, of course, a large percentage of these contaminants reach destinations other than their intended targets.

They can easily pollute the water in the form of runoff from the fields, as well as contaminating the air when sprayed aerially. Other issues include improper disposal and leakage from storage tanks.

When water becomes contaminated by pesticides, fish and other aquatic life can be harmed as a result. Plants can die because of herbicide application, for example, which diminishes oxygen levels in the water and suffocates the fish.

Physiological and behavioural changes in fish have also been seen because of pesticide exposure and other sources of pollution, including the likes of nest abandonment, failure to avoid predators and reduced immunity to disease.

In August last year, a report was released by the RSPB, WildFish, Buglife and The Pesticide Collaboration revealing that rivers around England are now exhibiting signs of increased chemical stress, as well as declining invertebrate diversity, with the number of waterways given a ‘poor’ or ‘bad’ rating more than doubling compared to previous years.

As well as a decline in the diversity of riverflies (aquatic invertebrates that are vital for maintaining a healthy ecosystem), drought conditions are exacerbating the situation, with lower water levels reducing the dilution of chemicals and accelerating the impact that chemical pollution is having on river ecosystems even further.

This is particularly concerning given the heatwaves, dry weather conditions and record temperatures that were seen in 2022, something that could well be seen again over the coming months.

In fact, the National Drought Group issued a warning back in February that England is just one hot dry spell away from being badly affected by severe drought conditions once again, with East Anglia, Devon, Cornwall and the Isles of Scilly still in official drought status.

How can pesticide pollution be addressed?

Without appropriate mitigation measures in place, climate change and population growth will put even more pressure on the water environment from chemicals like pesticides.

As well as drought leading to less dilution in rivers and increasing chemical concentrations, more frequent higher intensity rainfall events will see more chemicals washed into waterways from land and the sewage system.

The Environment Agency’s strategic approach to chemical management in waterways aims to protect aquatic life from chemical exposure, as well as protecting surface and groundwaters from chemical contamination in order to not compromise use for drinking supplies, and reducing human and wildlife exposure in the food chain.

It also works to identify chemicals of concern so as to prioritise them for action through sustainable cost-beneficial solutions for both wildlife and people alike.

However, the recent Troubled Waters report from the RSPB made further recommendations for the government in order to address the challenges presented by chemical use. This included making the move to regenerative farming practices and encouraging sustainable, nature-friendly food consumption.

Incentivising farmers and landowners to transition to agro-ecological farming would deliver a more effective cycling of nutrients, driving down reliance on chemical-based pest control and improving benefits to nature. More nature-friendly eating, meanwhile, would help improve water quality around the country and achieve a reduction in carbon emissions.

And, of course, use of technology could prove particularly beneficial where pesticide use is concerned… something that is currently being explored by utility company Southern Water.

The water firm is now trialling the use of drone technology to help farmers target pesticides only where they need, helping to protect the environment while cutting costs.

Currently, ten arable farmers are currently investigating the use of the Skippy Scout system to see how effective it is to locate weeds and target the application of herbicides.

It forms part of a wider scheme run by the company, which is working with farmers to raise awareness of herbicide loss and improve drinking water quality through the likes of precision farming and cultural measures (such as the use of cover crops and herbal leys to get on top of grass weeds).

Zoe Fothergill, senior catchment management officer at Southern Water, said: “The drone trial is already providing positive feedback from Western Rother farmers and their agronomists, who’ve used Skippy Scout, to support cropping decisions and inform spray operations.

“The mapping has also been useful in comparing different break crops, supporting a more diverse rotation.”

The Skippy Scout project also aims to see if it’s possible to reduce the amount of pre-emergent herbicides being applied through the monitoring of crops and weeds over a period of a couple of years.

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