Buried soils, archaeological remains and deposits

Overall vulnerability

Feature(s) assessed:

• Buried soils, archaeological remains and deposits

Special qualities:

• Landscapes that tell a story of thousands of years of people, farming and industry

Feature description:

Buried soils are soils that lie beneath later sediment. They are found under natural deposits or human-made deposits and structures.

They are an important source of archaeological information as they represent former ground surfaces or past human activity.

Archaeological remains tell us about the past and give an insight into human life and development. Remains can include a wide range of human-made items including tools, weapons and even fragments of clothing. For an assessment of biological deposits, see section ‘Palaeoenvironmental remains and sequences’ and for an assessment of present day soil, see section ‘Healthy soil’.

How vulnerable are buried soils, archaeological remains and deposits?

Buried soils, archaeological remains and deposits in the PDNP have been rated ‘high’ on our vulnerability scale. This score is due to high sensitivity and exposure to climate change variables. Their current overall condition is difficult to ascertain, but they have a moderate adaptive capacity.

One of the key potential impacts to archaeological remains is drier summers and wetter winters which could cause direct damage and also change how the land is used. Previous drainage of bogs and other soils coupled with development, farming practices including ploughing have caused damaged these features already. Archaeological remains cannot recover once they are lost. Although work is taking place to restore PDNP wetlands, this is reliant on funding being available.

Current condition:

The condition of buried soils and archaeological remains is difficult to ascertain, as there are many that are still to be discovered; however there are factors known that help highlight areas at greatest risk.

The survival of archaeological remains and deposits is dependent on the environment into which it was originally buried. It has been found that certain materials are better preserved in acidic environments while others are better preserved in alkaline environments.

In the Dark and South West Peak for example, peat bogs are a very important due to their value in preserving buried archaeology. This is because numerous materials survive better in anoxic environments i.e. those without oxygen. The waterlogged nature of these bogs means that the majority of soil microorganisms along with fungi are not able to operate as decomposers.

Unfortunately, PDNP peat bogs are generally in an extremely poor condition with a low or erratic water table (see assessment of ‘Blanket Bog’) which means it is likely that some items have already been lost or degraded. Previous human drainage of bogs and other soils across the PDNP will have already degraded or destroyed buried soils and some archaeological deposits. In addition, ploughing, development and other farming practices are very likely to have affected the condition of these features.

What are the potential impacts of climate change?

Overall potential impact rating

Direct impacts of climate change

Buried soils and archaeological remains could be significantly impacted by climate change. Increased surface water run-off in extreme storm events could see peatlands damaged and hydrology impaired as gullies are formed and widened, putting archaeology at risk. River valleys at risk of flooding could also experience a significant impact on archaeological remains. There may be changes to the water table or degradation of riparian habitats. Extreme rainfall and flooding could also cause erosion to underground mines, spoil heaps from lead mining, and steep earthworks. Data Certainty: High

Drier summers could also have a significant impact on sites with good organic preservation. Drying of soils may increase the cracking of the surface allowing oxygen to enter the subsurface region and increase microbial action activity and oxidation of materials. In addition, the cycle of wetter winters and drier summers will cause further damage to waterlogged archaeological deposits. In PDNP peat soils in particular these changes could see the destruction of organic remains. Data Certainty: High

Increased annual temperatures could also accelerate microbiological activity that could lead to the destruction or degradation of organic remains that are sensitive to such change. Data Certainty: Moderate

Human behaviour change

Drier summers could lead to changes in the economics of upland farming. For example, drier heathlands become more suitable for intensive management and grazing regimes may be changed. Erosion may be increased by overgrazing and high stocking levels, damaging remains and deposits. Agricultural improvement may lead to changes in soil chemistry - such as pH. This could affect preservation of materials. Data Certainty: High

Temperature changes leading to longer growing seasons could see new types of crops planted and marginal farming areas becoming more viable. Pasture converted to arable crops and associated ploughing and drainage may disturb soil layers while physical buried remains could be damaged. Data Certainty: High

Increased pressure for construction of renewable energy installations such as wind turbines, particularly on exposed areas, could affect the feature, as soils will be sensitive to installation of equipment, compaction and disturbance. This may cause an increase in erosion and change the hydrology or an area leading to drying of the site. However, current planning policies make renewable energy installations such as wind turbines on PDNP moorlands less likely. Data Certainty: Moderate

Invasive or other species interactions

If warmer winters lead to higher populations of burrowing mammals such as badgers, moles and rabbits buried archaeological deposits could be disturbed and hydrology of the area in question could be changed, with drier sites leading to less preservation of organic materials. Data Certainty: Moderate

Buried archaeological deposits could be sensitive to more rapid scrub and tree colonisation as a result of increases in atmospheric carbon dioxide and nitrogen levels and increased average annual temperatures. Not only can they be disturbed directly by root systems, but an increase in evapotranspiration could lead to drying of some sites. Data Certainty: Very Low

The fragile surface of damaged bogs is sensitive to increased erosion if winter storm events increase in frequency and intensity. In other habitats the areas where trees are uprooted and remains are therefore exposed or damaged could increase. Erosion may lead to more opportunities for invasive species to colonise, potentially drying soils further and increasing the risk of damage to remains and deposits. Data Certainty: Very Low

Nutrient changes or environmental contamination

Atmospheric changes that result in the chemical composition of water being altered could have an impact on the anoxic environment where it depends on microorganisms that are sensitive to such changes in water chemistry. If this environment is not maintained some remains may be lost or damaged. Data Certainty: High

Sedimentation or erosion

Degraded bogs in particular are sensitive to erosion, so an increase in summer droughts and winter storms could result in bare peat damaged by water and wind. This also applies to other soils across the PDNP. However, the deposition of eroded sediment could protect other sites. For example, while some archaeology could be exposed by increased erosion, some could also be buried further by the silt and material that has been moved. The uncovering of new sites and materials through increased erosion should only be considered a positive result of climate change if there is resource to record the new information - exposure is more likely to see the new sites damaged or lost. If erosion rates increase, remains and deposits may also be exposed to oxygen as the water table falls. Data Certainty: High

Other indirect climate change impacts

Drought and drier ground conditions could lead to an increased incidence of wildfire in the PDNP, particularly on degraded bog and heath sites. Potentially large areas of peat and vegetation could be lost further increasing erosion and peat loss. In such conditions dry peat also becomes more susceptible to damage from managed burns and there is more potential for them to get out of control. Fire can damage archaeological features within or below the peat and mean they are lost or severely affected. Efforts to manage fire risk could also impact archaeological features and deposits, for example flail cutting of firebreaks. Even if care is taken to avoid such features to minimise the risk of damage, this in itself may makes them more vulnerable to wildfire damage, as they are surrounded by fuel. Data Certainty: High

What is the adaptive capacity of buried soils, archaeological remains and deposits?

Overall adaptive capacity rating

All archaeological remains, deposits and features are unable to recover or regenerate from damage, so have a low adaptive capacity in this respect. Data Certainty: Very High

Although they can be found across the PDNP in a wide diversity of locations, some of the most sensitive places are probably the waterlogged peatlands. Because these are hidden features, it is unknown exactly where important remains can be found lowering the capacity for human adaptation measures to be implemented. Data Certainty: Moderate

Some money from grants and partners is available for peatland restoration activities, but there is currently a decrease in the uptake of agri-environment schemes in the PDNP. The future of agricultural subsidies after the UK’s exit from the European Union is currently very uncertain. Archaeological deposits, apart from those in peat, are at risk because they often do not have sources of funding available to secure the habitat in which they are situated and the vast majority have no form of statutory protection. Those areas that do not come under planning control and do not have funding sources available to secure them outside of agri-environment schemes will be some of the least adaptable. Data Certainty: High

There are several organisations in existence that are able to carry out or oversee peatland and other habitat restoration projects in the area, in order to help safeguard these features. Organisations include Moors for the Future Partnership, National Trust, Royal Society for the Protection of Birds and South West Peak Partnership. These increase the capacity for adaptive measures such as habitat restoration to be taken. However, only a small proportion of the park is in public ownership and the involvement of private landowners taking advantage of current land enhancement opportunities will be mixed in uptake and extent. Data Certainty: High

Information and expertise is available from the organisations highlighted above and others including Historic England and PDNPA Planning and Cultural Heritage teams. Data Certainty: Low

Key adaptation recommendations

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.

• Habitat enhancement to stabilise the water table, which will create stable environmental conditions for preserving remains and deposits.
• Integrate heritage protection into moorland restoration schemes.
• Appropriate management of the overlying habitat to prevent/minimise indirect damage from e.g. erosion, wildfire, root disturbance due to scrub growth or increased burrowing animal activity.
• Phase out burning on blanket bog. Develop fire contingency plans, and ensure management of habitats reduces fire risk e.g. rewetting and increasing species or structural diversity. Influence visitor and behaviour management plans and practices to minimise ignition risk.

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.

• Investigate funding for strategic survey to locate and catalogue sites of archaeological interest and potential (deposit modelling) in order to identify where habitat enhancement or management needs to take place to protect buried archaeology.