Chemical pollution killing off England’s riverflies, experts warn

Fears for river ecosystems as average number of species declines

Chemical pollution is killing off the invertebrate species that are the basis of England’s river ecosystems, with experts raising the alarm over falling diversity of mayfly, caddisfly and stonefly species.

A census of aquatic wildlife on 12 English rivers found that in the spring and summer 2021, the mean number of riverfly species detected had fallen. In autumn last year, an average of just 10 species were recorded in each sample, compared with 13 in 2016.

The findings come as the government considers a new “chemicals strategy” to reduce chemical pollution as part of its 25-year environment plan. Green groups are calling on ministers to take a dozen key steps they say could ameliorate contamination – but particularly to tackle chemicals from agriculture.

Stephanie Morren, the senior policy officer at the RSPB, said: “It is not acceptable that the pressure on rivers from chemical pollution is getting worse and impacting wildlife.

“We are living in a nature crisis, and we urgently need [the] government to take action. Given that such a significant amount of water pollution is from agricultural sources, it is vital that farmers are supported to reduce their reliance on inputs such as pesticides.”

Sarah Haynes, coordinator at the Pesticide Collaboration, said: “It often takes decades to realise the true harm of pesticides and other chemicals on our environment. Once the damage is done and a pesticide gets banned, a new chemical will enter the market … and so it goes. Enough is enough. As the movement for nature-friendly farming swells, the government needs a proper plan to reduce pesticide use and help revive our rivers.”

In the UK, more than 4,100 invertebrate species spend at least part of their lifecycle in freshwater. “Riverflies play many vital roles in our freshwater environment. They help to break down and filter organic matter and provide a food source for fish, birds, and mammals. Their presence is the standard indicator of the health of the habitat they live in,” Craig Macadam, the conservation director at Buglife, said.

Exposure to chemical pollutants causes a range of problems for these invertebrate communities, leading from arrested development all the way to death. The different tolerances of the various aquatic invertebrates can allow scientists to determine the scale of the chemical impact at a particular site.

“Looking at this data has allowed us to determine if, and how, chemicals are impacting aquatic wildlife, and whether the problem is getting better or worse,” researchers said in a report published on Tuesday.

The report used Species at Risk scores – which are calculated from the diversity and abundance of invertebrates present in a river – generated from the riverfly census.

The findings showed that in autumn 2021, the number of sites achieving “poor” or “bad” on the chemical stress scale was considerably greater than in 2015, 2016 and 2017, suggesting chemical pollution, from sources such as agricultural pesticides and pharmaceuticals, was getting worse.

Dr Janina Gray, the deputy CEO of the charity WildFish, said: “Chemical pollution isn’t a new problem. In fact, Rachel Carson warned us of its threat in her book Silent Spring in 1962.

“The results of the chemical report show that invertebrate communities are more stressed now than they were in our previous study, indicating the problem is getting worse. The upcoming chemical strategy is an opportunity to reverse the trend, but only if government steps up to the mark and acts now.”


Damien Gayle

The GuardianTramp

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