Photo: Alan Hale
The impacts of climate change on the historic environment will vary enormously depending on the type of historic asset and location. Some of the projected extreme weather events will undoubtedly have a significant impact upon certain classes of historic environment asset, but it is the projected long term trends, such as hotter drier summers, a longer growing season and rising sea levels that potentially have the greatest impacts.
Out of all the historic assets assessed, it is likely that historic landscapes will be most affected by climate change, with all of the four identified climate change scenarios – warmer mean temperatures, hotter drier summers, warmer wetter winters/wetter summers, more frequent extreme weather – all having an overall adverse impact. A series of potential impacts have been identified and assessed as being of moderate significance: cumulatively these are of high significance.
Historic assets (including historic buildings, historic settlements, archaeological sites and landscapes) lying below the one metre contour are assessed as being at significant risk from rising sea levels coupled with more frequent storm surges. Parts of many of Wales ‘ urban areas lie in this zone, and thus the potential damage and loss, not just to individual historic elements, but also to the overall historic character is considerable.
The scale and frequency of flood events will potentially have severe impact on historic assets. Historic buildings (listed and unlisted) and their fittings will be significantly affected, not just by the sudden impact of a flood, but in the longer term by damage caused by fungal and insect infestation, and by compromising structural integrity. Damage may occur to historic street furniture, street surfacing and other historic elements of settlements. Archaeological sites and structures such as historic bridges will be damaged and destroyed as rivers shift their courses.
The most damaging impact on historic buildings will be caused by more frequent flooding events, outlined above. In addition a series of moderate negative impacts on historic buildings caused by climate change have been identified, including damage caused by pests and diseases, drying and shrinking of clay soils, freeze-thaw effects on wet stone, more frequent maintenance required due to damper conditions, and damage caused by more frequent high winds and storms. Pests and diseases may be a particular issue for those historic houses that retain their original decoration, fixtures and fittings.
The predicted hotter, drier summers will cause the desiccation of some areas of upland peats making them more susceptible to erosion, erosion that will be exacerbated by the predicted higher winter rainfall and more frequent storms. In addition, in the long-term, peaty and organic soils could be transformed into mineral soils, with consequences for the historic landscape. Loss of blanket bog will expose archaeological sites and deposits that have been sealed and protected for several thousands of years, making them vulnerable to erosion.
Rising sea levels combined with more frequent and violent storms, will impact on the wide range of archaeological sites found on the foreshore, although the significance of the impact will vary widely according to local conditions. Also at risk are buildings, archaeological sites and landscapes along the coast edge, either in low-lying locations or on exposed cliffs.
The impacts of climate change on historic parks and gardens are difficult to assess as they will vary enormously according to the type of park of garden, and there will be positives as well as negatives. The most significant negative impact will occur in unmanaged parks and gardens where trees and other plants lost to pests, diseases and storm damage will not be replaced, and the speed of degradation and erosion of ‘hard’ garden features will increase under more frequent storms. In managed parks and gardens these losses will be largely made good and in parks and gardens celebrated for their exotics, hotter, drier conditions may be an opportunity to enhance their character.
Some of the best preserved archaeological sites in Wales are located in upland environments and so by their very nature are sensitive to change. More frequent and intense storms will result in erosion of these sites, but the main threat could result from the opportunity offered by warmer mean temperatures and a longer growing season to push back the boundaries of farmland into the margins of this zone.
The adaptive, dynamic nature of sand dune habitats makes any prediction as to how they might respond to climate change problematic. However, in general terms, it is likely that a rise in sea levels and an increase in the frequency of intense storms and gales will result in changes to dune systems, impacting on the large number and important archaeological sites within and below them. However, dune systems are generally carefully managed, and thus change might be mitigated.
Ancient woodlands are similar to other historic assets in that they contain complex evidence for past human use. Climate change is considered the greatest threat now faced by ancient woodland. These threats include the migration of pests and diseases, stress on trees caused by hotter drier summers and more frequent and intense storms. However, woodlands are complex and varied ecosystems, and are therefore likely to respond in a variety of different ways, and although they are sensitive to climate change, this change will be mitigated to some extent by the careful management enjoyed by some ancient woodland areas. Thus although climate change on woodland will have the greatest impact on the woodland itself, mass loss of trees and subsequent soil erosion, change of land-use and replanting could impact on individual historic assets lying within woodland.
A longer growing season resulting from higher mean temperatures will not directly impact on archaeological sites on farmland, but it is the opportunities offered by these changes such as increasing the amount of land under cultivation, the introduction of new crops and other changes to farming practices that could have a significant impact.
This report is concerned with the direct impacts of climate change on the historic environment. Adaptive responses to climate change, mitigation to reduce the threat of climate change and opportunities offered by climate change on the historic environment are not considered.
This plan aims to encourage collaboration and action across all sectors that will:
increase our knowledge and understanding of the threats and opportunities for the historic environment from changing weather and climate in the short, medium and long term
increase our capacity by developing the awareness, skills and tools to manage the impacts of climate change on the historic environment
build the resilience of the historic environment by taking action to adapt and respond to the risks, reduce vulnerability and maximise the benefits.
The sector adaptation plan is aimed at policy and plan makers, including the Welsh Government, local authorities and other public and third sector organisations, as well as non-governmental organisations, including academic institutions. All of these organisations have a vital role to play in developing and implementing the actions identified in the plan.
Climate change adaptation pilot project 2020-21 – PDF report (opens in a new window)
In 2020-21 Dyfed Archaeological Trust undertook at project that adopted a GIS based approach to provide clear identification and understanding of the threats and impacts of climate change on the Welsh historic environment as identified by the Historic Environment and Climate Change in Wales Sector Adaptation Plan 2020. The governing principle was that the assessment of the impacts of climatic change on the historic assets should be evaluated in first instance by where they are not by what they are.
Climate change rivers and riparian environments 2021-22 – PDF Report (opens in a new window)
This project is funded by Cadw and links in with DAT’s Climate Change Adaption Scoping Project, which aims to identify valleys at high, medium or low risk depending on a range of factors. The main risk of climate change being more severe and more frequent flooding events that will increase the rate of existing natural erosion and degredation. In the shorter term NRW’s and West Wales Rivers Trust (WWRT) programme of weir removal is a threat to numerous historic weirs, as are local authority programmes of bridge replacement and maintenance.
Climate change and shoreline management plans 2021-22, PDF report (opens in a new window)
The Welsh coastline has been divided up by Shoreline Management Plans (SMPs) into 928 sections known as policy units. Each of these units define how the specified section of coastline will be managed in the short-term, medium-term, and long-term. The historic environment is a consideration of shoreline management, however, HER data which informs SMPs is not current. This project will provide up to date data on historic assets in the areas covered by the action plans. This report sets out the methodology used and the results of a pilot project.
Other Trust projects address specific climate change threats to the historic environment:
https://www.dyfedarchaeology.org.uk/wp/discovery/projects/st-patricks-chapel-whitesands-st-davids/
https://www.dyfedarchaeology.org.uk/wp/discovery/projects/porth-y-rhaw-coastal-promontory-fort/
