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Limestone Pavements: Geology and ecology in harmony

(C) Tony Gill

Dr Tim Thom, Wild Ingleborough Programme Manager, takes a deep dive into this fascinatingly-formed landscape.

Limestone pavement is a rare and irreplaceable geological landscape, made up of flat expanses of limestone with deep cracks along natural joints (called grykes), forming separate blocks (clints). It is also one of our most plant-rich habitats, and supports many scarce or rare species. 

How is it formed?

Rock from life

To visit Ingleborough 330 million years ago during the Carboniferous era, when Yorkshire was on the equator, you would be snorkelling in a shallow, warm tropical sea in a climate more like the Caribbean than the cool uplands of today. You would be swimming amongst large shellfish - snail-like goniatids and clam-like bivalves, coral reefs and forests of filter-feeding sea lilies. As these died and dropped to the seabed, their shells and skeletons formed thick layers of calcium carbonate which eventually turned into limestone.
 

Wild Ingleborough Limestone Pavement - Sara, Telling Our Story Volunteer

Known for its botanical richness the limestone pavements at Ingleborough are thought to have been formed by glaciers 30 million years ago, during the Carboniferous period - Photo taken by Sara

Time, ancient seas and ice

Over the next few hundred million years, land masses moved north and oceans and Ice Ages came and went. Each of these events either added more calcium carbonate or dissolved some away, etching the limestone that remained into clints and grykes. At the end of the last Ice Age, the 1,000m thick glaciers acted as mighty bulldozers and scoured the Dales of millions of years of geology, re-exposing the Carboniferous limestone pavement as the ice receded.

Acidic rain

After the ice, wind-blown silt and debris covered the limestone pavement in an Arctic-style tundra, which gradually became woodland as the climate warmed. Rainwater seeping through the vegetation and soils picked up acids that dissolved the calcium carbonate in the limestone, creating yet more eroded features.

People and animals

Finally, people began clearing woodlands and grazing animals, creating open scrub. Soil was blown away or washed underground through cracks and holes and the limestone pavement once again reappeared. Although the formation of new pavement stopped, wind, rain and frost continued to mould the pavement into runnels, pans, pits and solution cups, creating niches for a range of plants to grow in.

View across the limestone pavements at Ingleborough, inebtween the pavements there are ferns and trees growing in this unique habitat.

Limestone pavements at Ingleborough - (c) Tony Gil

Why is it so unique?

“Grykes, clints and reduced grazing at Scar Close and Southerscales have created an incredibly diverse mix of habitats.”
 

Dr Tim Thom, Wild Ingleborough Programme Manager

A history of damage and neglect

It is not geological forces that have had the biggest impact on our limestone pavements. Over the centuries, stone from pavements was used in construction, walling and lime-making, culminating in the most damaging impact of all - a craze for water-worn clints in garden rockeries dating back to Victorian times.

A Dalesman article in 1954 reported that 8-14,000 tons of clints were removed annually from Ingleborough, and this practice continued into the 1990s until 95% of limestone pavements had been damaged or destroyed.

Plants that grow on limestone pavement are also vulnerable to grazing, as demonstrated by the photograph of Scar Close on Ingleborough. One side of the fence has not been grazed since the 1970s, and is now one of the best places for wild plants in the UK. The other side is heavily grazed by sheep with a clearly visible stark difference.

photograph of Scar Close on Ingleborough. One side of the fence has not been grazed since the 1970s, and is now one of the best places for wild plants in the UK. The other side is heavily grazed by sheep with a clearly visible stark difference.

The effects of removing grazing at Scar Close - no grazing on the left for 50 years. (c) Tim Thom

Recovery

Pavement destruction was finally ended in the UK as a result of campaigns by the Limestone Pavement Action Group and legal protection through Limestone Pavement Orders in the late 1990s. We can’t replace the lost clints but, with extraction stopped and less grazing, limestone pavements can recover to become rich botanical habitats.

We are lucky at Ingleborough to have three of the best examples in the world to demonstrate how - Scar Close, Southerscales and Colt Park Wood.

Grykes, clints and reduced grazing at Scar Close and Southerscales have created an incredibly diverse mix of woodland, limestone grassland, exposed rock and upland heath.

Wild Ingleborough has driven a programme of grazing changes and species restoration for the areas of limestone pavement in the programme area, with the hope that all remaining limestone pavement will match these incredible botanical hotspots.

We need your help to protect and restore the remaining areas of limestone habitat.

£

Cor gryke-y!

  • The UK has about 2,700 hectares of limestone pavement, with a third of this in the Yorkshire Dales.
  • Ungrazed limestone pavement acts as a refuge for around 20 species that are nationally rare or scarce.
  • Between 34,000 and 41,000 tonnes of limestone pavement was removed from Ingleborough until it became a protected landscape – the equivalent weight of around 250 houses.
birds eye views of plants in the cracks of limestone pavements.

(c) Greg Armfield - WWF 

Limestone pavements provide a huge range of different conditions for a variety of plants to thrive:

The depths of damp and shady grykes are perfect for woodland plants like hart’s tongue fern.

Further up the grykes, rigid buckler fern and bloody cranesbill respond to the increased light and, in the dry cracks at the top, drought-resistant wall lettuce and maidenhair spleenwort find a home.

wild thyme on a limestone pavement

Wild thyme (c) John Potter

Where thin soils develop on clints, limestone grassland plants like rock-rose, thyme and blue moor-grass thrive.

On Scar Close, domed islands of deeper soil support heather and bilberry shrubs.

4 purple flowers on a long greren stem with a yellow centre.

Birds-eye primrose (c) David Berry

On the stony clint tops, pits and shallow depressions hold water and create miniwetlands for butterwort and bird’s-eye primrose. On drier clints, drought tolerant biting stonecrop and rueleaved saxifrage tough it out.

At Colt Park, a strip of pavement has never been cleared or grazed. As a result, it has deeper soils on clints which support an impressive woodland of stunted ash, hazel and rowan, with a rich array of flora including globeflowers, wood crane’sbill and herb Paris.

A beautiful pink sunrise over Ashes Pasture.

Ashes Pasture - (C) John Potter

Ingleborough needs you!

Donating to Wild Ingleborough is a chance to contribute to a flagship landscape scale restoration programme in one of England’s most iconic landscapes.
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