A new global study has found that at least 80% of sites on the UNESCO World Heritage list are already burdened by climate stress, with nearly one in five sites (19%) constructed of key materials that are threatened, such as stone and wood.
The study showed that if the world follows a “low-emission” path — where strong global action is taken to cut pollution and limit climate change to safer levels, while keeping global temperature rise below 1.5° Celsius (2.7° Fahrenheit) above preindustrial levels — about 40% of threatened sites could be protected.
However, global greenhouse gas emissions are rising, with a trajectory for around 2.5-3°C (4.5-5.4°F) of warming by 2100, closer to a “medium-emission” path. Under this scenario, far fewer sites would be spared, according to the study.
In an increasingly warming world where climate change effects are growing worse each year, researchers decided to analyze the status of humanity’s most renowned historical sites made of stone and wood. The team analyzed the past (1961-91), present (2010-40) and future (2070-2100) climate risks to World Heritage sites by mapping the exposed surfaces of buildings with 3D models, which provided a site-level index of climate stress.
Interestingly, the researchers found that no single mitigation strategy could equally protect the sites due to regional and material variations, the study reveals.
Read also: Nigerian government validates NAP document to address climate change
Haiyang Cui, who is the corresponding author of the study and a professor at Guizhou University in China, noted in an email to Mongabay that the key motivation for the global-level study was to conduct a material-specific assessment. “Our goal was to help countries prioritize where to save first when budgets are tight,” he said.
Among the most striking findings of the study: a stark Global North-South divide in heritage conservation.
While more than 40% of affected heritage sites are in Europe and North America, the same fragilities play out differently in the Global South.
Haiyang said that climate risks are determined by differences across climate zones, such as tropical monsoon areas, subtropical coastal regions and arid inland zones and cannot be approached from a country-specific or continent-specific lens. However, he noted that low- and middle-income countries often face greater pressure from compound climate events but have the least access to conservation resources, creating a Global North-South divide in conservation efforts and impacts.
“Temperature, humidity, and weather patterns determine climate risks,” he said. For instance, in subtropical coastal climates, such as those found in Brazil, Morocco or China, he said that problems like salt spray, erosion and storm surges are especially severe. Whereas in tropical monsoon regions like Southeast Asia, heritage sites built from stone such as Angkor in Cambodia or the Borobudur Temples of Indonesia, face constant exposure to high heat, high humidity and heavy rainfall. “Often, these climatic conditions also trigger secondary effects, such as invasive plant roots or termite activity, which may damage structures from within,” he said.
The professor further explained a notable case in the mosque complexes of Isfahan, Iran, where delicate architectural elements are increasingly exposed to thermal stress. “Even in temperate inland Europe, recent years have brought more frequent heatwaves and dry wind events,” he noted.
Moreover, in places like the Old City of Zamość in Poland, the number of severe climate events has increased sharply, raising concern among conservation professionals, Haiyang said, explaining how stone and wood are made of fundamentally different components and react differently to climate change. “Stone dislikes sudden swings in heat and humidity, whereas wood suffers when it gets wet and then dries again, repeatedly.” The frequency of these climate jolts over the years, and the historic sites’ exposure to them, determine the stress thresholds for stone and wood.
“The type of threat varies greatly depending on local climate, and understanding this variation is essential to designing protection strategies that actually work in different parts of the world,” he noted.
Story was adapted from Mongabay.
