Farm measures could cut river pollution by 22%, study finds

Cover crops, buffer strips and wetlands could reduce phosphorus pollution entering rivers by more than a fifth, but climate change threatens to weaken their effectiveness, new research warns.

An Environment Agency study published on Monday (9 November) found that combining the three farming measures could significantly reduce nitrogen and phosphorus entering waterways.

However, researchers warned that future changes in rainfall and temperature could undermine their benefits, raising questions about the long-term effectiveness of environmental improvements on farmland.

The findings come as farmers face growing pressure to reduce agricultural runoff and improve water quality through more sustainable land management.

The study examined the potential impact of cover crops, vegetated buffer strips and small in-field wetlands across two predominantly rural river catchments: the Eden and the upper Thames.

Using computer modelling, researchers assessed how the measures could reduce nutrient pollution under past and future climate conditions.

In the Eden catchment, combining all three approaches was estimated to reduce total phosphorus loads by 22% and nitrogen loads by 17%.

The predicted benefits were smaller in the upper Thames, where phosphorus loads could fall by 5% and nitrogen loads by 8%.

These reductions were modelled using climate conditions from 2000 to 2019, rather than measured following the installation of the measures on farms.

Researchers found that combining the interventions delivered greater overall reductions than using them individually.

However, their effectiveness varied considerably between catchments, highlighting the importance of local conditions when deciding where environmental measures should be introduced.

The study also suggested that targeting areas further upstream could deliver proportionally greater improvements in water quality.

Cover crops help protect soil between main cropping periods, while vegetated buffer strips can intercept nutrients washed from farmland towards watercourses.

Small in-field wetlands can also capture and process nutrients carried by surface water before they enter rivers.

Despite their potential benefits, the research raised concerns about how these approaches could perform as Britain's climate changes.

Scientists examined future conditions between 2020 and 2040 and between 2060 and 2080, using climate projections based on a high-emissions scenario.

The modelling suggested that changing rainfall and temperature patterns could reduce the overall effectiveness of nature-based measures, although their performance would vary seasonally.

Buffer strips and cover crops were found to deliver greater nutrient reductions during cooler, wetter months, while in-field wetlands generally performed better during summer.

However, wetlands were predicted to become less effective at reducing nutrient concentrations later this century.

Between 2060 and 2080, in-field wetlands were estimated to reduce phosphorus concentrations by up to 3% and nitrogen concentrations by up to 4%.

That compared with reductions of up to 6% during the earlier 2020 to 2040 period.

The Environment Agency's report warned: "Climate change is likely to reduce the effectiveness of these NbS to manage diffuse nutrient pollution."

The findings suggest that farmers and land managers may need to consider future weather patterns when planning environmental improvements, rather than relying solely on current conditions.

Researchers also stressed that the success of such measures depends heavily on their design, location and management.

Agricultural nutrient pollution remains a major challenge for England's waterways, with nitrogen and phosphorus contributing to poor ecological conditions in many river catchments.

Although the research supports the potential benefits of nature-based approaches, scientists acknowledged important limitations in their findings.

The modelling was validated against observed nutrient concentrations from 2000 to 2019, but there was insufficient observational evidence to verify the predicted effects of the individual interventions.

The reported reductions therefore represent potential catchment-wide improvements rather than results already demonstrated on farms.

The Environment Agency concluded that cover crops, buffer strips and wetlands could play an important role in reducing agricultural pollution when combined with wider catchment management measures.

However, it stressed that environmental interventions must be carefully designed and managed to remain effective as climate conditions change.

The study, commissioned by the Environment Agency's Chief Scientist's Group, was undertaken by researchers from JBA Consulting and Lancaster University.

Its findings highlight the potential for nature-based farming measures to improve river health, while reinforcing the need for long-term planning as climate change places growing pressure on the countryside.