By Eleanore Heasley
Picture your idyllic afternoon. Mine would be walking next to a crystal clear stream overflowing with life; green plants, splashing salmon, rustling water vole – all of which should be characteristics of England’s 224 chalk streams. Sadly, this image was shattered when I read the headline of the WWF’s 2014 report on The State of England’s Chalk Streams: “The results are clear: England’s chalk streams are in a shocking state of health“1. The WWF stated that 77% of chalk streams were failing to achieve Good status in the Water Framework Directive’s ecological classification, which requires water bodies to have high biodiversity, habitat and water quality. But with such a bleak prognosis, is it worth trying to restore the dream of the UK’s chalk streams?
The answer is yes, because chalk streams are important hubs of biodiversity. Their underlying chalk geology creates stable temperature and flow conditions as well as clear waters; ideal conditions for life. These pristine waters support diverse invertebrate communities, which in turn sustain large fish populations, including species popular with anglers, such as brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). They are also perfect habitats for charismatic animals like the otter (Lutra lutra) and water vole (Arvicola amphibius), which are key conservation species.
The streams also provide ecosystem services to their local residents. For example, the underground stores of water that feed chalk streams, chalk aquifers, provide 70% of the drinking water for South East England. They also supply nutrients to streams, boosting aquatic vegetation, which can help slow flooding.
What are the current challenges facing chalk streams?
Alarmingly, chalk streams are more likely to be classified as Poor or Bad status than the average UK river. The Environment Agency’s Reason for Failure report2 from 2013 highlights the primary causes behind UK chalk streams failing to meet Good status – physical modification by humans. Modifications such as channel straightening, dredging, confinement and weir construction, were identified as the primary cause of failure in 34% of chalk streams2. They can strip streams of their natural resilience, rendering them unable to adjust to extreme flood or drought events.
Pollutants entering from sewage and agricultural sources are the primary cause of failure in 14% and 10% of chalk streams respectively. Severe sewage pollution incidents can cause huge numbers of fish deaths, and the Environment Agency found in 2014 that all the water companies operating in chalk stream areas are below target performance in managing these incidents3.
Chalk streams are particularly vulnerable to agricultural pollutants, as their catchments contain a higher proportion of arable land than other English catchments. Fine sediment from arable land enters rivers and smothers salmon and trout eggs in spawning gravels, which is one of the key reasons why salmon and trout fisheries are categorised as ‘at risk’ in chalk streams. Pollutants from these sources also contain a nutrient called phosphate. Phosphate encourages the growth of algae, restricting oxygen and light available for aquatic species to survive, in a process known as eutrophication. Chalk streams are particularly vulnerable to eutrophication as they have naturally high nutrient levels, so small inputs of pollutants can have huge environmental effect.
Nearly a quarter of chalk streams failed due to over-abstraction, which is the removal of water from the stream or aquifer for use in irrigation, industry or drinking water, beyond sustainable levels. The abstraction lowers the output of streams, increasing the concentration of the nutrients that drive eutrophication.
Invasive species are also putting additional pressure on chalk streams, with species such as Japanese knotweed (Fallopia japonica) and Himalayan balsam (Impatiens glandulifera) outcompeting native flora, and the signal crayfish (Pacifastacus leniusculus) restricting the range of the native white-clawed crayfish (Austropotamobius pallipes) to just 5% of chalk streams.
What does the future look like for chalk streams?
The drive for river habitat improvement across the UK has seen over 300 water bodies receive improvements funded by the £24.5mn Catchment Restoration Fund4. Steps have been taken to improve the state of chalk streams specifically, with increasing support for conservation from rivers and wildlife trusts, anglers and the public, which has led to some success stories. For example, otters have slowly been returning to chalk streams.
However, the WWF’s report states that improvements to date have been “too little, too niche, too slow”, and urges in their manifesto for the Government, water companies and NGOs to work to “reduce abstraction, decrease pollution, revive natural river processes and improve habitat and promote better river management”. The WWF’s 2014 manifesto pushed for a focus on chalk streams in the Environment Agency River Basin Management Plans for 2016-2021. The plans, released in February 2016, include projects specifically aimed at improving chalk stream environments, with financial commitment from Defra and the Environment Agency5. For instance, in the Thames River Basin District Affinity Water has agreed to help protect chalk streams in the Chiltern Hills and North Downs by limiting abstraction and improving efficiency, in the Humber River Basin District 10km of the River Hull chalk stream habitat is being restored, and in the Anglian River Basin District phosphate-hungry plants are being introduced in the River Mun chalk wetlands to reduce harmful nutrient levels.
The proposed improvements highlighted in the River Basin Management Plans take positive steps towards protecting and enhancing one of England’s irreplaceable gems – our chalk streams.
1. WWF (2014) State of England’s Chalk Streams
2. Environment Agency (2013) Reason for Failure report. Referenced in WWF (2014) State of England’s Chalk Streams.
3. Environment Agency (2014). Interim classification data from 2013. A method statement for the classification of surface waters. Cited in WWF (2014) State of England’s Chalk Streams.
4. Defra (2015) Catchment Restoration Fund: Environment Agency Final Annual Report 2014-15
5. Defra (2016) River basin management plans: 2015.