Pollution and climate change hamper biological recovery of rivers
Sewage spills, agricultural pollution and climate change may have slowed the biological recovery of rivers in England and Wales, a study suggests.
Researchers studying invertebrates that live on riverbeds found their numbers had increased by nearly 10 per cent from the early 1990s until 2018 â but that recovery has since slowed down.
Researchers from Cardiff University analysed nearly 50,000 invertebrates collected from about 4,000 streams and rivers. Emma Pharaoh, a researcher at the universityâs school of biosciences, said: âInvertebrates are important indicators of river health, reflecting pollution and other human impacts. By looking at the types of invertebrates living on the riverbed, we can get a good picture of river health.
âUp to 2018 the number of invertebrate families in our rivers increased by nearly 10 per cent and communities were comprised of more pollution-sensitive invertebrates. We also found that despite urban rivers historically being the most polluted, they showed the greatest improvements â taking them closer in quality to rural rivers.â
However, the research showed that some improvements in rivers in England and Wales appear to have slowed, possibly reflecting the effects of emerging water quality problems from sewage, agricultural pollution, climate change and new forms of pollution, including microplastics and pharmaceuticals.
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The study found that increases in the number of pollution-sensitive invertebrates continued across the full study period but âat a slower rate over the last ten yearsâ.
The research, published in the journal Science of the Total Environment, said the results âindicate that recovery is gradually slowing down, perhaps as the main improvements from existing legislation and wastewater handling and treatment are exhaustedâ. The authors of the study added: âUnless recovery is complete, new initiatives may be needed to extend these improvements.â
The study also highlighted how invertebrate communities in predominantly agricultural catchments, both arable and improved grassland, were âtypical of degraded streams, similar to heavily urbanised catchmentsâ.
Steve Ormerod, deputy chairman of Natural Resources Wales, said: âUrban river improvements since the early 1990s reflect the combined effects of industrial decline, improved regulation and investment in wastewater treatment. But hints of a more recent slowdown show how we need further action â especially from regulators, water companies and agriculture â to regain and maintain the positive trends.â
The study used data from the Environment Agency and Natural Resources Wales and updated analysis from ten years ago, also by Cardiff University, allowing the researchers to investigate trends over decades and across countries.
Last year sewage was dumped into UK waterways on more than 300,000 occasions, a decrease from the previous year but only because of exceptionally dry weather, the agency said.
The government has said it is making water companies invest ÂŁ56 million into improving the infrastructure to reduce pollution, and that awareness of the scale of the problem is because of improved monitoring.
Ceri Davies, of Natural Resources Wales, said: âWhile we have made good progress in protecting and enhancing our waters over recent decades, this study is a stark reminder that there is still a long way to go.
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âThe challenges facing our rivers may evolve with time but the need for concerted and collaborative action to conserve them remains. Now is a pivotal time for change, not complacency, and an opportunity to once again accelerate improvements to our rivers.â
The Times is demanding faster action to improve the countryâs waterways. Find out more about the Clean It Up campaign.
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