Show caves and caverns

Overall vulnerability

Feature(s) assessed:

• Show caves and caverns

Special qualities:

• Landscapes that tell a story of thousands of years of people, farming and industry
• An inspiring space for escape, adventure, discovery and quiet reflection

Feature description:

Within the PDNP, there are four show caverns. Treak Cliff, Blue John, Speedwell and Peak caverns are all situated around Castleton in the White Peak. There are further examples just outside the boundary of the PDNP - Poole’s Cavern in Buxton and the Masson and Rutland Caves at the Heights of Abraham in Matlock Bath.

Although there are other caves in the PDNP, the focus of this assessment is the show caverns and the potential impacts of climate change on their condition and sustainability as visitor attractions. In Castleton, the cave systems run much further than where the public are taken on tours, and are only accessed by cavers.

Peak Cavern has a large cave entrance but is part of a much larger cave system. In recent years, it has expanded its offer and is now an evening venue for concerts and film screenings. Speedwell Cavern was once a lead mine and opens out into a network of natural caves and rivers. The tour for the public is by boat.

Blue John and Treak Cliff Cavern are both accessed on foot and feature locations where Blue John was, and still is, excavated. This unique mineral, of which there are 15 distinct veins, is used in jewellery.

The show caves and caverns provide evidence for former methods of industrial working which forms an important part of their tourism interest.

Most of the land in the Castleton catchment is, like the show caverns, under private ownership. The National Trust does own some of the land at Winnats Pass and Windy Knoll. Peak Cavern is part of the Duchy of Lancaster and is tenanted.

How vulnerable are show caves and caverns?

Show caves and caverns in the PDNP have been rated ‘moderate’ on our vulnerability scale. This score is due to moderate sensitivity and exposure to climate change variables, a relatively stable current condition, and a moderate adaptive capacity.

An increase in flooding of the caverns is one of the key potential impacts of climate change. This could mean they close for longer and more regularly resulting in the attractions possibly becoming more seasonal. Changes in water levels and associated erosion could potentially damage historic features within the caves and caverns.

All four show caverns are in private ownership and appear to be reasonably sustainable businesses however it is not known what financial resources they have to invest in adaptations, and the range of changes that could be made is relatively limited. The feasibility of investing in natural flood management techniques in the catchment that feeds the caverns should be investigated.

Current condition:

Castleton is a ‘honey pot’ village and is a very popular location within the White Peak for visitors and cavers. The four show caverns are open almost all year round – unless they are flooded.

Speedwell and Peak are active stream caverns and are connected. The water from both converges and forms the main underground drainage for the catchment area. Both were impacted by several periods of heavy rain in 2019. Speedwell was closed due to flooding for at least ten days, six of which were during the school holidays. Peak Cavern was closed for at least one day, but on several other dates only short tours of the entrance chamber could be offered as the inner part of the cavern was flooded.

Castleton caves have some of the highest known levels of radon gas in any cave system, and this has to be monitored on an ongoing basis.

Several of the caverns are units of the Castleton Site of Special Scientific Interest (SSSI). A partnership has been set up by Natural England and local cavers to monitor the condition of the SSSI, which has shown them to be in a favourable and stable condition in recent years.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

Caves are sensitive to flash flooding and also drying out in summer droughts - particularly Speedwell Cavern where access is by boat so the water level can be too low or too high. Caverns could be closed to the public for an increased number of days, affecting profitability and position as a visitor attraction. These extreme conditions could also affect the historic features in the caves. Data Certainty: Moderate

Dry ground after drought periods may lead to periods of rapid run-off during intense summer storms. An increase in flooding of caves from such storms has the potential to be a risk to public safety, and thus to impact business sustainability. There could also be an increase in levels of carbon dioxide in caves during dry and still weather. Data Certainty: Moderate

The rate of erosion of limestone features could rise if continued increases in atmospheric carbon dioxide mean water becomes more acidic. This could affect processes sensitive to alterations in water chemistry such as stalactite formation. While this is unlikely to have a significant impact in the short term, it may affect the caverns as a scientific resource. Data Certainty: Moderate

Temperature changes could affect the levels of radon as its concentration depends on the temperature relative to the average temperature in the cavern interior. Increased concentrations are found during warmer weather so there may be a need for increased monitoring and ventilation of caverns. It is however unlikely to have a significant overall impact. Each system is unique in terms of ventilation and layout so it would be difficult to predict the response of each cavern. Data Certainty: Low

Human behaviour change

If the supply of visitors is disrupted by flooding events affecting access on the PDNP transport network, cavern businesses could suffer financially. Less reliable visitor numbers could affect profitability and their long-term future as a tourist attraction. The construction of new flood defences or re-routing of water could have varied impacts on the caverns. The hydrological network is very complex and the consequences of measures to prevent flood are unknown. Data Certainty: Low

Visitor businesses rely on maintaining footfall. If fewer tourists visit the area in wetter winters, cavern businesses may become more seasonal, creating a need to adapt and diversify. Data Certainty: Low Conversely hotter, drier summers could increase visitor number as people seek cooler places. Increased footfall at show caves could secure their future as a tourist attraction if the infrastructure is able to cope with rising numbers. Hotter drier summers could also affect the cave catchments. If pastoral farming is no longer sustainable, they may evolve into a more wooded landscape. This could reduce the speed of run-off, reduce flooding in the caves, and improve water quality entering system. Data Certainty: Low

Invasive or other species interactions

Increased atmospheric carbon dioxide and nitrogen coupled with increased annual average temperatures may lead to more rapid growth and longer growing season for vegetation around visitor facilities. Vegetation around cavern entrances may require management to occur regularly. Data Certainty: Low

Nutrient changes or environmental contamination

The condition of water in cavern systems is closely tied with that of water at the surface. In limestone landscapes, the many cracks and tunnels mean that cave water is sensitive to sources of pollution at the surface. Fertilizer applied for agriculture, coupled with milder weather could see warmer, nutrient-rich water entering cave systems and potentially creating better conditions for pathogens to reproduce. The overall impact though is likely to be relatively small. Data Certainty: High

In addition, larger volumes of water flowing into the caverns after storm events could carry in an increased amount of organic material. Rotting material can cause a rise in underground carbon dioxide concentration. This can compound the effect of high numbers of people on carbon dioxide. However, carbon dioxide levels can easily be monitored, and this process is unlikely to have a significant impact on this feature. Data Certainty: Low

Sedimentation or erosion

Access to parts of the cavern systems could become more restricted by sedimentation if storms become more frequent and severe. Historic features could also become buried or damaged. Access for recording and survey could also be reduced. Data Certainty: Low

Wetter winters could see greater movement of sediment into caves and some tunnels sealed due to the high volume of water. This may encourage radon build up in places and increase the need for monitoring and ventilation. Conversely increased water flow could increase ventilation and reduce radon levels in places. This is however unlikely to have a significant overall impact. Each cavern will have a unique response depending on its layout, ventilation and other factors so impact is difficult to predict. Data Certainty: Low

Other indirect climate change impacts

An increased risk of wildfires during hotter, drier summers could reduce visitor footfall in the PDNP due to access issues. There is also potential for increased soil erosion after fires leading to increased sedimentation in caverns - although this is unlikely to have significant impact. Data Certainty: Low

What is the adaptive capacity of show caves and caverns?

Overall adaptive capacity rating

Physical recovery from extreme events should be possible unless tunnels are blocked by large amounts of debris. However, financial recovery from repeated closure or reduction in business could be more difficult. It is unlikely that new show caverns in other locations could be opened. This is due to a lack of suitable large sites and planning constraints on new infrastructure. Impacts of climate change would also likely to be similar elsewhere, and new sites would need to be near a tourist centre. Data Certainty: High

Although there is diversity in ownership and structure within the four existing show caverns and the drainage of water into and out of each, they are located within a very small area and therefore will likely be exposed to similar changes. They share many similarities and constraints in terms of access and the infrastructure of Castleton. This decreases the adaptive capacity of the resource. Data Certainty: High

The PDNP show caverns are in varied private ownership. Three are run through limited companies incorporated at various times - Speedwell Cavern in 1973 and Peak Cavern in 1997, which are run by the same company directors, and Treak Cliff Cavern in 1998. Currently they all appear to be reasonably sustainable businesses but individual ability to invest in adaptation is unknown and likely to be mixed. Speedwell currently appears to have the largest assets, but the reliance on boat transport may mean it has a more limited scope for adaptation. Data Certainty: Moderate

Peak Cavern and Speedwell Cavern are within the Castleton SSSI, and condition monitoring is carried out in conjunction with cavers. While SSSI monitoring increases the likelihood to identifying problems and enabling them to be addressed, the designation could potentially make adaptation measures less likely to occur. If adaptations are deemed detrimental to the cave system, or if the administrative burden of interacting with public bodies such as Natural England deters future cavern owners, they may be less likely to be put in place. Data Certainty: Low

Management options for adaptation are quite limited. Although improving cave ventilation, air monitoring systems and upgrading infrastructure are possible; options for the management of watercourses to reduce flooding incidence and severity are much more limited. Data Certainty: Moderate

Key adaptation recommendations for show caves and caverns:

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.

• Ensure cave management plans consider need for increased ventilation, and continue to monitor levels of radon and other gasses such carbon dioxide into the future.
• Ensure planning policies are flexible and open to sympathetic adaptations for caves that do not harm historic significance.

Improve current condition to increase resilience: Increase structural diversity of the landscape to improve resilience to change

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 landscape in which the feature is found. By doing so the condition of the feature, and therefore its resilience to climate change impacts, should be enhanced

• Encourage natural flood management techniques within the catchments feeding the caverns – for example allow some pasture to revert to scrub or woodland in suitable places.
• Reduce farming inputs such as fertilizers, or paper pulp into system, to improve water quality and reduce toxin build-up in caves. Livestock levels should be lowered around streams and rivers as slurry is the main contributor to nutrients in rivers. Give consideration to good management of waste to improve catchment quality, including effective slurry store management. Low nutrient feed should be encouraged. Fertiliser and pesticide inputs should also be reduced to prevent spread into the watercourse.