England’s chalk streams support a wide variety of biodiversity; but anthropogenic pressure destroys these icons of English culture
The world has fewer than 300 chalk streams – and England has most of them. These currents only occur where chalk cliffs meet the surface of the earth, which is rare in the world.
Their stable, cool, nutrient-rich water enables the chalk streams to support an exceptionally high number of species – so much so that these habitats are sometimes called “England’s rainforests“.
Unfortunately, although some of them are teeming with life, the health of the English Chalk Rivers is threatened by a multitude of human activities. As a result, many of the country’s – and therefore the world – chalk rivers are not reaching their ecological potential.
In their flowing areas, wild trout and grayling can patrol oxygen-rich reefs and pools, hunting for the aquatic juveniles of mayflies and other insects. Kingfishers lurk on branches above, occasionally diving below the surface in blue-orange bolts to catch unsuspecting minnows.
Elusive mammals, including otters and voles, sometimes swim underwater alongside lush flower beds, such as the water crowfoot, whose flowers are held expectantly above the surface of the water and attract bees and other pollinating insects in the summer.
In their headwaters, these streams can naturally disappear in summer and leave their channels dry. Our research has shown that dry canals are often populated by land-based insects, including some species that are nationally rare.
Their water reappears in winter and so the streams are known locally as winter bournes. Because these streams naturally alternate between wet and dry conditions, they allow aquatic and land species to share a habitat at different times.
Specialists like the Winterbourne stonefly are rarely found in perennial streams, but they are together in winterbourne chalk brooks. Their various life stages are carefully timed to coincide with the creek’s fluctuations between wet and dry. Young insects develop in the water and then hatch as flying adults before the dry phase begins.
Under the chalk stream itself, in the cold darkness of the aquifers below, blind, colorless crustaceans live hidden and quietly contribute to the ecosystem biodiversity.
Your underground lifestyle made this possible old british to survive tens of millions of years through successive ice ages that caused the extinction of other freshwater animals.
What makes chalk streams so special? Everything starts under our feet. Rainwater flows deep into the chalk landscape of south and east England and forms underground aquifers.
Filtered through the chalk, the groundwater springs in gin-clear, nutrient-rich streams that support photosynthetic plants and microorganisms – fuel for food webs that feed on everything from grazing insects to predatory fish, birds and mammals.
Chalk currents also benefit people. Catching wild brown trout from an English chalk stream is the dream of many discerning fly fishermen. Besides, yours is physical and mental well-being can be improved simply by staying near rivers and streams.
Winterbourne’s chalk streams are special. Our research shows the deep emotional connection people can have with this unique environment. Some report mood swings that shift from sadness to hope and joy that coincide with the creek’s seasonal transitions between dry and wet phases.
The threat of pollution
Many chalk aquifers – the source of chalk streams – are unfortunately polluted by nitrogen and phosphorus from fertilizers applied to arable land. The apparently clear water of chalk streams is therefore often contaminated with invisible impurities.
The natural course of many, perhaps most, chalk streams in England has been straightened and diverted to make way for agricultural, urban and industrial uses. Many are dwindle to a trickle as water companies take water from both streams and the aquifers below.
ONE strategy Restoring England’s Chalk Streams was published in October 2021. Welcomed by the environmental agency and Natural England recommends that chalk streams be granted a new legal protection that reflects their globally unique value for ecology and culture. To better protect our chalk rivers and to ensure that these ecosystems remain worthy of their iconic status, radical measures are needed.
Rachel StubbingtonProfessor of River Ecology, Nottingham Trent University; Kieran J. GethingPhD student in ecology, Nottingham Trent Universityand Tim SykesPhD student in environmental life sciences, University of Southampton
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