New study reveals where condition of rivers has declined since 1990
13 December 2024
Despite widespread improvements in river health between 1991 and 2019, researchers discover worrying signs for some of the most biologically diverse rivers.
A new study led by researchers at Cardiff University’s School of Biosciences has mapped the changing health of rivers across England and Wales.
Using data collected over 29 years from nearly 4,000 streams and rivers, change was assessed by looking at the range of invertebrates that live on the riverbed – a long-established, sensitive indicator of ecosystem health.
Several recent studies using invertebrates have found overall improvements in river health after 1990 across England and Wales. This new study is the first to look in detail at how the change is spread across the country and reveals several areas where the condition of rivers has declined.
The study underlines the challenges of determining the cause, with evidence that the importance of local land use, water quality and other factors vary across England and Wales.
Lead author, PhD student Emma Pharaoh, said: "Against a background of general improvement, this new study provides a more nuanced view of post-1990 changes, showing where improvements and declines have occurred.
It suggests that problems are emerging in rivers fed by the uplands, in addition to rivers in the south-west of England and Wales in particular.
Dr Ian Vaughan, who supervised the project, said: "Worryingly, many of the declines are affecting the highest quality rivers, so whilst many of the historically most polluted rivers have improved since 1990, we may be losing the crowning jewels.
There is unlikely to be a single cause, but pressures linked to intensifying agriculture and climate change are implicated and our results suggest that the effects of excess nutrients and climate warming may be increasing through time.
The research is a collaboration between Cardiff University, the Environment Agency, Natural Resources Wales and University of Waterloo, Canada.
The findings were published in Science of the Total Environment: Potential drivers of changing ecological conditions in English and Welsh rivers since 1990.
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