Edinburgh Castle is named as one of the world’s historic sites at risk from the world’s changing climate, finds Sandra Dick

Perched atop its craggy volcanic rock, Edinburgh Castle stood strong in the face of enemy attack for centuries, providing a haven for Scottish nobles and a vantage point for the nation’s armies.

With parts dating from the 12th century and its instantly recognisable ramparts, it may seem almost indestructible.

Now – perhaps as a wake-up call not to take arguably Scotland’s most famous building for granted – Edinburgh Castle has been included in a major global project aimed at highlighting the risks that historic structures face from climate change.

Edinburgh Castle features alongside four international heritage sites including Rapa Nui, otherwise known as Easter Island, renowned for its collection of tall stern-faced statues.

With no reef surrounding the Pacific Ocean island to protect its fragile coast and their positioning on light, mineral-poor soil which easily runs off into the ocean, the enigmatic Moai are at risk of damage from rising sea levels.

As well as highlighting the risks brought by changing weather, the project shows how 3D modelling and a range of other innovative processes have been used to create highly accurate models, drawings and digital images to provide preservation teams with vital knowledge of their every corner and crevice.

As well as helping to build action plans, the drawings and models are being used as a baseline to identify erosion in years to come and guides for repairs and restoration.

Edinburgh Castle and Easter Island feature in the online project alongside the ancient desert mud city of Chan Chan in Peru, which is threatened by drought and flood, Bagerhat in Bangladesh, where salt water is eroding the centuries-old mosques, and the Tanzanian port city of Kilwa Kisiwani, where buildings are being affected by coastal erosion.

In Edinburgh Castle’s case, the Heritage on the Edge project shows how rising levels of rainfall, combined with the porous sandstone and increasing incidents of wetting and drying, freezing and thawing, leave the structure at risk of decay.

Meanwhile, rainfall saturating the ground aiding the erosion of the

Castle’s volcanic rock is said to pose a potential safety risk to pedestrians, vehicles and tourists, as well as impacting on the very foundations of the ancient structure.

Spanning 60 pages on Google’s Arts & Culture platform, Heritage on the Edge draws together photography, 2D maps, 3D models and historical background plus interviews with conservationists to hammer home the risks facing built heritage, the significance of the sites, and the battle against the changing weather.

It highlights the work of California-based 3D-surveying firm CyArk, which since 2003 has used pioneering technology to digitally record, archive, and share images and data related to some of the world’s most famous sites.

As well as mapping Edinburgh Castle, CyArk’s technology has been used to map Skara Brae in Orkney, the Antonine Wall, Roslin Chapel and John Muir’s Birthplace in East Lothian, New Lanark, St Kilda, Stirling Castle, and Edinburgh’s Old and New Towns.

While it uses lasers to make 3D scans of structures, high-resolution imagery is captured at ground level and by overhead drones to create highly accurate drawings and detailed maps.

Dr Ewan Hyslop, head of technical research and science at Historic Environment Scotland (HES), said: “We are seeing the effects of climate change right across our estates. “We are also seeing quite startling statistics – the average rainfall in Scotland is now 20-25% higher than it was in the 1960s, temperatures have risen, sea levels have risen. It’s warmer and wetter.

“The growing season is a month longer than it was in the 1960s, so there is more vegetation growing and more cleaning out gutters. And when you are managing monuments and castles, all of that is significant.”

He added: “3D scans give us a snapshot in time and are a very accurate view of what these monuments are like. We can then go back in some cases after two years to rescan them and see where there is evidence of decay.

“Edinburgh Castle, like many other sites, is very exposed, and our job is to maintain and protect it for the future.”

Thermal imaging and microwave moisture monitors are also being used to pinpoint dampness in ancient stone walls and track sources of water leaks – a major challenge in complex and large structures such as Edinburgh Castle.

Software companies, meanwhile, are working on programmes which could help estimate the impact certain weather conditions may have on centuries-old walls. Hyslop added: “The key is not to be reactive. It’s about being proactive and knowing what you are dealing with.”

Two years ago, the Government agency, which manages almost 340 castles, Neolithic sites, abbeys and ruins across Scotland, issued red warnings indicating a need for urgent protection on almost one-fifth of its sites. Amber “high risk” warnings were placed against 70% of the agency’s properties.

It warned that many sites were exposed to risks such as flooding, coastal erosion and slope instability which are expected to be exacerbated by climate change.

Some, such as Fort George near Inverness, 800-year-old Inchcolm Abbey in the Firth of Forth and Brough of Birsay, a Pictish and Viking-settled island in Orkney, were identified as being at particular risk and requiring protection.

Edinburgh Castle received a red warning due to the risk of landslide and groundwater flooding. But because of the high level of supervision by HES, it was also given an amber rating.

However, concern over the impact of climate change on Scotland’s built heritage spreads beyond ancient monuments to privately-owned buildings such as Georgian terraces, Victorian villas and sandstone tenements which could also be adversely affected by wetter and more extreme weather conditions.

Hundreds of coastal heritage sites around the country have also been identified as at risk from rising sea levels and erosion.

Last month, HES issued its Climate Action Plan 2020/25 which includes a pledge to enhance monitoring of climate change impacts with remote sensing and satellite data, crowdsourced imagery and “citizen science” projects.

Already members of the public are being encouraged to upload photographs of certain historic structures to help HES preservation teams to monitor changes.

Speaking in a video presentation linked to the Heritage on the Edge project, David Harkin, climate change scientist at HES warned: “Climate change really is the defining issue of our generation.

“There’s not been anything like it in the past. If we don’t get a handle on it, we risk losing some of our historic assets that we quite rightly are proud of.”

For more information about the Heritage on the Edge project, simply search “Heritage on the Edge” in your search engine.

The other sites at risk

As well as Edinburgh Castle, the Heritage on the Edge project spotlights the risks facing four other key cultural sites:

Chan Chan, Peru: Once the largest earthen city in pre-Columbian America, Chan Chan is under threat from heavy rain, floods, drought, strong winds and storms from El Nino. Humidity increases salt contamination and encourages vegetation, damaging the foundations.

Bagerhat, Bangladesh: The ancient coastal city of mosques and mausoleums is in danger from rising sea levels and changes in salinity affecting the structure of the 600-year-old buildings.

Kilwa Kisiwani, Tanzania: Once the wealthiest city in East Africa and an important coastal centre of trade and commerce, Kilwa Kisiwani faces rising sea levels and coastal erosion which has already led to the loss of some structures.

Rapa Nui, Easter Island: Rising sea levels, droughts and soil erosion place the enigmatic structures in peril. Work is under way to strengthen ocean-facing walls and protect the statues for future generations.