Frustration at ‘decade of decline’ at Wiltshire and UK chalk streams

Monitoring at five sites on the River Avon, which flows through Wiltshire and Hampshire, has found a significant decline in wildlife such as freshwater shrimps, mayflies, caddisflies, beetles and aquatic bugs over the past decade. 

Conservation charity WildFish said the declines in invertebrates showed the Government was not doing enough to protect precious chalk streams - even ones such as the Avon, which have the highest conservation status and flows through Warminster, Amesbury, Pewsey and Devizes. 

The charity is calling for government bodies such as the Environment Agency and Natural England to set more ambitious environmental standards to assess the health of the streams. 

The monitoring, carried out in partnership with the Wiltshire Fishery Association as part of the SmartRivers citizen science project, reveals the diversity of invertebrates fell by 17 per cent and numbers were down by more than three quarters (77 per cent) in average annual counts between 2015 and 2024.

The situation for riverflies, which are sensitive to pollution and a good indicator for the wider health of the river ecosystem, was even worse, with the monitoring revealing the diversity of the river's species has fallen by 25 per cent.

The report also said the average abundance of the insects was down 83 per cent in 10 years.

Despite the declines, official assessments found the monitored sites all scored as high quality for invertebrates in 2015 and were still high or good quality in 2024.

WildFish’s Dr Janina Gray claims the statutory standards set the bar too low for high levels of invertebrates.

As a result, the official monitoring can conclude all is well in the river despite major declines in key species, and make action and investment to protect them more difficult, she warned.

Chalk streams, with their clear, flowing water fed from underground chalk aquifers and springs, provide habitat for an array of wildlife including Atlantic salmon, brown trout and water crowfoot, as well as water resources for people.

There are only around 200 in the world, most of them found in the southern half of England, making them an internationally rare habitat.

But they are suffering from “death by a million cuts”, according to Dr Gray, with pressures on water quality driven by nutrient pollution, sediment and chemicals from water treatment works, agriculture, and road run-off.

They are also threatened by over-abstraction of water, reducing the flows in the river and making pollution more concentrated.

Dr Gray, head of science and policy at WildFish, said: “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.

“It’s just about hanging in there.”

She added: “It just shows that the bar is not set high enough to properly protect chalk streams.”

And she warned: “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.”

All chalk streams should be designated as Special Areas of Conservation (SAC), WildFish argues, joining the handful of such waterways which already have the classification.

And current assessments and protections do not go far enough and need to be properly enforced.

“We would like the Environment Agency and Natural England to revise the standards for chalk streams to raise the bar to protect them,” Dr Gray said.

A spokesperson for the Department for Environment, Food and Rural Affairs (Defra) said: “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.

“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.

“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.”

To protect chalk streams, Wiltshire has the Wiltshire Chalk Partnership which aims to create an additional 2,000 hectares of semi-natural grassland across Wiltshire and to connect and restore important existing habitats.

It says: "The River Avon and its tributaries are the arteries of this landscape, but are in a heavily degraded state from centuries of being re-shaped for different purposes.

"Isolated from its floodplain and the surrounding landscape, the river and streams are struggling to cope with the pressures from agriculture and wastewater systems, offering limited opportunities for riverine and wetland wildlife.