Fifty years of transformation on iconic limestone pavements has unveiled a varied picture for one of the UK’s most unique landscapes. This information stems from the first nationwide evaluation in five decades of the vegetation and plant life in Britain’s rare limestone pavements, highlighting significant changes since the 1970s.
Fifty years of transformation on iconic limestone pavements has unveiled a varied picture for one of the UK’s most unique landscapes.
These landscapes, recognizable to those who have visited the Yorkshire Dales and fans of the Harry Potter series, have seen a decline in specialized species in many areas, while more common, less desirable species have thrived.
Nonetheless, it’s not solely negative news, as some regions of the UK’s limestone pavements have experienced an increase in plant diversity.
The results come from a comprehensive national evaluation, the first in fifty years, focusing on the vegetation and plant life in the rare limestone pavements of Britain, carried out by Carly Stevens, a Plant Ecology Professor at Lancaster University.
Britain’s limestone pavements are significant habitats primarily located in northern England’s Yorkshire, Lancashire, and Cumbria, along with parts of North Wales and Scotland.
Ferns and various herbaceous plants, usually found in woodland, heathland, and grassland areas, flourish in the deep slits and fissures of limestone pavements, known as grikes, often creating an unseen world until viewed from directly above.
In the early 1980s, new regulations were established to safeguard limestone pavements from quarrying, and many locations now enjoy the protection of nature reserves.
Despite being a unique and valued landscape, as well as a habitat for many specialized flora and fauna, Britain’s limestone pavements have not been extensively researched scientifically.
To remedy this, Professor Stevens repeated a survey of limestone pavements that was conducted by scientists Stephen Ward and David Evans in the early 1970s.
She aimed to use the same methods to replicate their study, surveying 3157 hectares of limestone pavements over five years from 2017 to 2022.
Her research, published in the journal Functional Ecology, documented 313 plant species across the UK’s limestone pavements—29 species more than recorded in the 1970s.
Moreover, some pavements reported an increase in the variety of plant species present.
However, in various regions, despite the protection provided by nature reserves, some undesirable species, including thistles, nettles, and bracken, have proliferated. Additionally, vital specialized species like primrose, lily of the valley, elderflower trees, and hairy violets have diminished in number across the UK’s limestone pavements.
The declines are not consistent, as some areas saw an increase in these species, contributing to a complicated yet significant scenario that offers crucial insights for conservationists.
“Limestone pavements have experienced considerable shifts in the types and numbers of plants inhabiting these rare and remarkable habitats,” noted Professor Stevens. “They’re critically important habitats and are safeguarded due to their unique geology and the diverse plants and animals residing there.
“To ensure their conservation for future generations, it’s essential to comprehend the reasons behind these changes.”
A primary factor influencing some limestone pavements is tree cover. Professor Stevens conducted aerial photo comparisons between historical images and current photographs of all limestone pavements in England to assess changes in tree quantity and size.
Her findings revealed that some pavements experienced more than a 50% increase in shaded areas due to trees. However, the number of treeless pavements also grew, illustrating the diverse conditions across different regions, largely influenced by surrounding tree density.
Pavements with increasing numbers of trees and shrubs typically saw a decline in plant diversity. Professor Stevens believes this is likely because trees and shrubs obstruct light for smaller plants nestled within the grikes. The most affected pavements are found in Lancashire and Cumbria.
Conversely, pavements with low or moderate tree cover showed a higher chance of increased species diversity—though not always with the preferred specialized types.
Professor Stevens noted that many open pavements have been affected by animal grazing, though there have been noticeable changes over the last five decades.
“Grazing pressure has diminished in many areas since the 1970s due to agricultural policies, but some pavements are still overgrazed,” Professor Stevens pointed out. “While grazing can play a crucial role in managing limestone habitats, it must be approached thoughtfully, as overgrazing can result in biodiversity loss. Similarly, under-grazing can lead to scrub and tree encroachment, further impacting diversity and species composition by reducing light availability.”
This survey will guide future management strategies for limestone pavements, an evolving area that will benefit from the results and additional data gathered.
“Currently, we do not have a clear understanding of what optimal management for limestone pavements entails,” Professor Stevens remarked. “This survey yields essential data to enhance our understanding of the existing state of limestone pavement vegetation. Nevertheless, further research is necessary to improve our knowledge of potential threats to the habitat and ways to rehabilitate damaged limestone pavements.”
The findings of this study are discussed in the paper titled “Large changes in vegetation composition seen over the last 50 years in British limestone pavements.”
