Limestone grassland

Overall vulnerability

Feature(s) assessed:

• Limestone grassland

Special qualities:

• Beautiful views created by contrasting landscapes and dramatic geology
• Internationally important and locally distinctive wildlife and habitats
• An inspiring space for escape, adventure, discovery and quiet reflection

Feature description:

Limestone grasslands - dominated by herbs and grasses - are found on base-rich, thin and well-drained soils overlying limestone geology. In the PDNP, around 1,200 hectares of limestone grassland has been mapped, all of this being priority habitat. The vast majority (98%) is found in the White Peak. This relatively small extent covers less than 5% of the area of the White Peak – mostly designated as Sites of Special Scientific Interest (SSSIs) and Special Area of Conservation (SAC).

Smaller undesignated areas are often confined to steeper slopes or rocky outcrops on the limestone plateau. The limestone grasslands that remain in the PDNP are internationally important - supporting a large diversity of species.

They support many rare plants including pyramidal orchid, spring cinquefoil and probably the largest British population of Jacob’s-ladder as well as butterflies such as the brown argus, dingy skipper and dark green fritillary.

How vulnerable is limestone grassland?

Limestone grassland in the PDNP has been rated ‘moderate’ on our vulnerability scale. This score is due to high sensitivity and exposure to climate change variables, but also a high adaptive capacity. Limestone grassland in the PDNP has a limited extent, but much of what remains is protected by SSSI designation. Overall habitat persistence is likely to be determined by non-climate or indirect human factors, for example changes in agricultural economics, with areas such as the dales likely to be impacted. The iconic Jacob’s-ladder grassland may be particularly vulnerable and in need of conservation actions.

Current condition:

A large proportion of the remaining limestone grasslands in the PDNP are classified as SSSIs, and in 2015, 58% of these protected sites were categorised as being in favourable condition. In unprotected areas, condition is more variable. Changes in levels and types of livestock are likely to have affected the quality and extent of the habitat since the 1940s. Increases to the periods in which livestock are housed, and a shift from sheep farming in the dales to dairy farming on the limestone plateau, may have affected the availability of suitable stock needed to maintain the habitat. Losses of limestone grassland to scrub encroachment (through lack of grazing) are known to have been significant, and a number of sites have probably been lost to plantation woodlands. Increases in plants such as thistles, docks, and nettles may have been exacerbated by disturbance and high nitrogen deposition, and non-native invasive species such as Himalayan balsam have spread into areas away from rivers.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

Climate change has the potential to have several negative impacts on PDNP limestone grasslands. Although the UK distribution of limestone grassland reaches further south and east than the PDNP (to areas with a hotter, drier climate) those within in the PDNP currently support several species of plant with a northern distribution – for example globeflower, melancholy thistle, mossy saxifrage and the Derbyshire County Flower Jacob’s-ladder. Therefore, although limestone grasslands are unlikely to be completely lost over the next century due to direct climate effects, they are likely to undergo changes in character and composition. Data Certainty: High

Hotter drier summers are likely to change the species composition of PDNP limestone grassland communities. Northern and upland compositions such as the National Vegetation Community (NVC) CG10, which is thought to require a mean maximum summer temperature of less than 24⁰C, may move towards southern and lowland compositions such as NVC CG2. Community composition changes may be greater on south facing slopes that receive more sunlight. Data Certainty: High

Similarly, NVC MG2 (tall dales grassland with Jacob’s-ladder) is thought to require 900 - 1650 mm of rain per year and more than 180 wet days, and may be the most vulnerable grassland community in the dales. This could shift towards NVC community MG1 (the mesotrophic Arrhenatherum elatius grassland) with the loss of species including the iconic Jacob’s-ladder. Data Certainty: High In addition, species which need frost to germinate (vernalisation) such as cowslip and yellow rattle are likely to decline as winters warm. Data Certainty: High

Drier summers mean that specialist mosses and fungi could also decline (see also ‘Waxcap fungi’) and deep-rooted stress-tolerant plants may become more dominant. Annual plants may benefit more than perennials – this can already be observed on south facing slopes in the Dales. Data Certainty: Low

Invasive or other species interactions

Increased levels of nitrogen may provide better conditions for species such as thistles and nettles, which in turn could lead to an increased use of herbicides. Data Certainty: Moderate In combination with increases in temperature, nitrogen deposition could potentially result in a higher proportion of grasses and fewer broadleaved species especially in areas which remain wet. Drier conditions, however, may help with the control of invasive species such as Himalayan balsam. Conversely increases in flooding events may spread seed from invasive species into new areas, while summer droughts and more extreme weather events may open grass swards and create more opportunities for invasion. Some rare winter annuals such as Hutchinsia may also do better. Data Certainty: Low

Human behaviour change

Changes to agricultural economics are difficult to predict, but have the potential for a major impact. Wetter winters may mean that livestock is increasingly housed over winter, while summer droughts may cause some areas to be unsuitable for grazing. The resultant changes in grazing regimes could cause a loss in some floristic elements, or even the loss of the grasslands through scrub invasion. Data Certainty: High

What is the adaptive capacity of limestone grassland?

Overall adaptive capacity rating

Limestone grasslands occur in a wide range of conditions and latitudes across the UK, with the lowland calcareous grassland climatic envelope going well south and east of the PDNP, although some key species are already at their southern range limit. Therefore, the overall habitat category may change in character and composition but is unlikely to be lost altogether. However, some already scarce types such as NVC CG10 (dales limestone grassland - northern type) and MG2 (tall dales grassland with Jacob’s-ladder) may be particularly prone to decline and increased fragmentation.

The current extent of limestone grassland in the PDNP is somewhat fragmented with limited connectivity, and is restricted to the White Peak. Natural England habitat opportunity map modelling shows areas of fragmentation for this habitat type. The dales are currently highly fragmented with a huge edge-to-surface ratio making them very vulnerable to adjacent agricultural activity.

Limestone grasslands, especially those that are longer established, have been shown to be relatively tolerant to atmospheric pollution and acidification, in part due to the base-rich soils on which they are found. Research shows that the dales may be important refugia sites for some species, with the diverse topography allowing some species to survive in “cool spots” such as north facing slopes. Coupled with the high species diversity, these factors provide more potential for habitat persistence and adaptation.

A large amount of the remaining limestone grassland in the PDNP is already protected (mostly as SSSIs), and existing work to improve condition has already contributed to safeguarding what remains against non-climate threats. Whilst improving condition cannot protect from climatic extremes, it should increase general resilience to change, and may partially offset some climate stressors. In addition, Environmental stewardship options are currently available (and likely to remain available) for the maintenance or restoration of semi-natural grasslands. Since these grasslands are managed habitats, human responses are likely to have a stronger influence on habitat persistence than the direct results of climate change, and therefore there is good scope for making adaptations.

Key adaptation recommendations for limestone grassland:

Improve current condition to increase resilience

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are aimed at improving the condition of the feature at present, therefore making it better able to withstand future changes to climate.

• There is scope for expansion of limestone grasslands onto some parts of the plateaux where limestone is close to the surface or exists as outcrops. Where expansion is limited by underlying geology, grading into continuous neutral grassland, heathland or scrub should be encouraged.
• Adapt management to avoid fertilizer inputs.
• Reduce non-climate sources of harm.
• Consider the impact on key views when planning adaptations.

Improve current condition to increase resilience: Targeted conservation efforts for important sites and at risk areas

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations are conservation measures aimed at those sites that will have the biggest impact for this feature – either because they are particularly important for the feature or because they are most at risk from climate change.

• Grassland in greatest need of considering conservation options further is perhaps MG2 Jacob’s-ladder grasslands.
• Restore priority areas where scrub has encroached, but maintain some scrub in the landscape.
• Work to identify the best refugia sites and ensure these are managed appropriately.

Improve current condition to increase resilience: Increase structural diversity to improve resilience at a landscape scale

The current condition of a feature is an important factor alongside its sensitivity and exposure, in determining its vulnerability to climate change. These recommendations focus on increasing the structural diversity of the area or habitat in which the feature is found. This can help to offset the effects of climate change on the feature, as well as to allow it to be in a better position to recover from future climate changes.

• Increase size and connectivity of existing patches, including connectivity with other habitat types in a mosaic.
• Increase connectivity by restoring species rich grassland. This should also increase resistance to drought and increase carbon capture.
• Increase wood pasture on the plateau. Increase trees in fields and along margins to help with summer drought and forage for stock.
• Have an integrated management plan for each of the Dales in the PDNP for the different habitats within them.

Adapt land use for future conditions

These recommendations are adaptations to the way in which people use the land. Flexibility in land management - reacting to or pre-empting changes caused by the future climate - should afford this feature a better chance of persisting.

• Adapt grazing regimes to allow for more flexibility of timing and stocking density. Accept changes to feature These recommendations are about adapting ways of thinking to be accepting of inevitable change. While some changes may be negative, this also presents a chance to seek out any positive opportunities that may be caused by climate change.
• Loss of some currently valued northern species but gain of more southern species may need to be accepted. Liaise with other protected landscapes (such as those further north) to share knowledge and management techniques.