A recent study conducted by Professor Carly Stevens of Lancaster University has revealed significant changes in the vegetation of British limestone pavements over the last fifty years. Limestone pavements are unique landscapes found mainly in northern England, Scotland, North Wales, and are known for their deep gaps and cracks known as grikes, which host a variety of plant species. While some areas have seen an increase in plant biodiversity since the 1970s, others have experienced declines, with less desirable species like thistles, nettles, and bracken becoming more abundant.
Despite being protected under nature reserve status in many areas since the early 1980s, limestone pavements have not been extensively studied scientifically. To address this gap, Professor Stevens replicated a survey conducted in the 1970s by scientists Stephen Ward and David Evans. Her study, published in Functional Ecology, recorded 313 plant species across UK limestone pavements, with an additional 29 species identified compared to the 1970s. While some species such as primrose and lily of the valley have declined, others have seen increases, leading to a complex and important picture for conservationists to consider.
One significant factor impacting the vegetation of limestone pavements is tree cover, with some pavements experiencing an increase in shaded areas due to tree growth. Professor Stevens found that pavements with higher tree and shrub cover tend to have lower plant biodiversity, likely due to light obstruction for smaller plants in the grikes. However, pavements with low to moderate tree cover have seen increases in species richness, though not always with desirable specialist species. Grazing pressure from animals also plays a role in habitat management, with overgrazing and under-grazing both posing threats to biodiversity and species composition.
The survey results will help inform future management strategies for limestone pavements, particularly in areas like Lancashire and Cumbria where tree cover has impacted plant biodiversity. While the survey provides vital data for understanding the current state of limestone pavement vegetation, further research is needed to determine optimal management practices and address threats to the habitat. The findings from this study highlight the importance of continued monitoring and conservation efforts to preserve the unique and diverse ecosystems found within British limestone pavements.