The fragile beauty of chalk streams: why they matter

By Sam Peters

As visions of bucolic English countryside go, nothing stirs the imagination quite so vividly as the sight and sound of a fly-flecked chalk stream burbling through a meadow on a hazy summer’s afternoon.

Described by David Attenborough as ‘one of the rarest habitats on earth’, chalk streams are almost unique to England.

Increasingly, belatedly, we are waking up to the need to protect and regenerate these most precious of habitats.

Arguably the most ecologically important jewel in England’s natural crown, for centuries England’s chalk streams, like our other watercourses, have been degraded by industrial processes, excessive extraction and the dumping of raw sewage.

But while it goes without saying all rivers need protecting – or at least it should – it is chalk streams above all which perhaps needs protecting most.

“Chalk streams make me think of clear, gently flowing water, water crowfoot, and kingfisher, uniquely English landscapes that feel both wild and fragile,” explains Daniel Combes, a young landscape designer quietly working to protect, regenerate and educate around our chalk streams.

The unique topography of areas including Hampshire, Wessex and East Anglia, where chalk bedrock meets the Earth’s surface, make their stable, cool, nutrient enriched waters globally significant ecosystems which some call ‘England’s rainforests’.

With an estimated 85% of the world’s 224 chalk streams situated on these shores, they are fed by aquifers created by porous chalk, which means rainwater absorbed into it appears, normally around six months later, from springs further downhill.

When this water emerges from springs, it does so at a remarkably constant temperature of around 10 degrees with a consistent flow, creating what are often referred to as ‘gin clear’ nutrient-rich streams which support a vast array of animals, photosynthetic plants and microorganisms.

These in turn provide food for webs which feed everything from grazing insects to predatory fish and mammals.

In healthy habitats, otter, kingfisher and water voles live along the banks, darting between the water crowfoot, flag iris and water starwort, while the flinty beds provide perfect spawning grounds for salmonoid fish (trout, grayling), which make them highly prized destinations for fly-fishers from around the globe.

Bullhead, brook lamprey and Atlantic salmon breed in clean gravels, and some chalk rivers provide a refuge for the increasingly threatened white-clawed crayfish. 

And it is precisely this diversity of wildlife and abundant natural tapestry which is drawing the most enlightened landscape designers and architects to champion chalk streams as an integral part of their design process.

Dan, having grown up in the Nadder Valley, alongside one of the chalk tributaries of the River Avon, understands how precious these systems are and the potential beauty they can unlock when in full health.

“Our main role at Daniel Combes Garden Design is to educate our clients about their value, understanding that a healthy chalk stream transforms a landscape, bringing with it a myriad of life and creating a more dynamic and beautiful landscape - put plainly - there is a direct correlation between beauty and ecological health

“These are uniquely English habitats which feel both wild and fragile, supporting a huge diversity of wildlife and act as natural filters for water quality.”

However, as with much of our natural world, chalk streams are threatened by human activity.

A combination of factors including pollution, over-abstraction of water, and physical modifications of their channels and floodplains place chalk streams under huge strain. This results in decreased water quality, altered habitats, and reduced biodiversity.

Sewage overflows, agricultural runoff (e.g. nitrates), and industrial pollution disrupt natural processes and harm aquatic life while excessive water extraction for agriculture, industry, and domestic use depletes stream flows, concentrates pollutants, and can lead to algal blooms, oxygen crashes, and toxicity.

Straightening, deepening, and diverting river channels, building weirs and sluices, and hard-surfacing floodplains restrict fish movement and can significantly reduce the overall ecological value of the chalk stream.

Meanwhile the loss of natural meanders, riparian vegetation, and gravel beds, which are essential for fish spawning and invertebrate habitats, further reduces the resilience and biodiversity of chalk streams.

But where there are problems there are also opportunities and Dan and his team are creating a portfolio of work which could dramatically improve our most precious waterways. Combes said: “We are currently working on a project in Dorset where we are trying to de-canalise a chalk stream. Our hope is to re-establish a wetland system in the bottom of the valley where the water is allowed to find its own course through the valley bottom. We hope to lower the phosphorus levels in the soil and establish a mosaic of wildflowers, scrubs and woodland.”

In many ways their work has only just begun and it will take a combination of education, awareness, expertise and hard work to deliver. But no one can doubt the value in it and the potential to provide life support to these overworked natural arteries of England.

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