One of England's precious chalk streams has suffered "a decade of decline" with wildlife numbers plummeting dramatically, conservation campaigners warn. Ten years of monitoring on the River Avon in Wiltshire and Hampshire reveals invertebrate numbers have crashed by more than three quarters.
The conservation charity WildFish conducted monitoring at five sites on the River Avon between 2015 and 2024 in partnership with the Wiltshire Fishery Association as part of the SmartRivers citizen science project. The study found diversity of invertebrates fell by 17 per cent while numbers dropped by 77 per cent in average annual counts.
Riverflies hit hardest
The situation for riverflies - insects sensitive to pollution that indicate wider river health - proved even more alarming. Diversity of riverfly species fell by 25 per cent while average abundance plummeted by 83 per cent over the decade.
Despite these dramatic declines, official assessments under the statutory water framework directive still rated the monitored sites as high or good quality for invertebrates. The contradiction highlights a fundamental problem with current environmental standards, according to WildFish.
Standards 'set bar too low'
Dr Janina Gray, head of science and policy at WildFish, warns the statutory standards fail to reflect the high levels of invertebrate life a healthy chalk stream should support. "The Avon is a SAC, it's the most protected river we have, and yet the abundance drops that we're seeing are dramatic in that time period," she said.
The inadequate standards mean official monitoring can conclude rivers are healthy despite major species declines, making protective action and investment more difficult to secure. "It's just about hanging in there," Dr Gray added about the Avon's current state.
Globally rare habitat under threat
Chalk streams represent an internationally rare habitat with only around 200 existing worldwide, most found in southern England. Their clear, flowing water fed from underground chalk aquifers provides crucial habitat for Atlantic salmon, brown trout and water crowfoot.
But these ecosystems face "death by a million cuts" from multiple pressures including nutrient pollution, sediment and chemicals from water treatment works, agriculture and road run-off. Over-abstraction of water further reduces river flows and concentrates pollution.
Call for stronger protection
"It just shows that the bar is not set high enough to properly protect chalk streams," Dr Gray warned. WildFish argues all chalk streams should receive Special Areas of Conservation designation, joining the handful already classified with this highest protection status.
"These ecosystems are globally rare and ecologically critical, but without immediate action, we risk causing irreversible damage to the very characteristics that make them so important," Dr Gray said. "We would like the Environment Agency and Natural England to revise the standards for chalk streams to raise the bar to protect them."
Government promises action
A Department for Environment, Food and Rural Affairs spokesperson said the new government prioritises cleaning Britain's rivers after years of damage. "Within this new government, our top priority is to clean Britain's rivers and restore them from years of damage. Chalk stream restoration is a vital part of this effort," they stated.
"We have secured £2 billion of funding from water companies to start cleaning them, while modernising the abstraction licensing system to ensure water is used sustainably and to stop damaging abstraction practises to the environment - a problem particularly pronounced in chalk streams," the spokesperson added. "This is part of our wider plan to rebuild the water system, including a record £104 billion investment to halve sewage spills by 2030 and the creation of a new, powerful regulator."
Sources used: "PA Media" Note: This article has been edited with the help of Artificial Intelligence.
