What is the future for our earthen heritage? Modelling the risk of environmentally-driven deterioration at sites located in dryland areas

Earthen heritage forms ~10% of UNESCO’s World Heritage List, with sites generally concentrated in dryland environments. Many sites are exposed to environmental processes such as wind, sediment movement and rain, which can result in extensive deterioration of the earthen heritage. To improve the effectiveness of conservation strategies that aim to minimise deterioration, there is an urgent need to understand how multiple environmental processes interact and impact earthen heritage, particularly over longer (centennial) timescales. We therefore apply the ViSTA-HD model (Vegetation and Sediment TrAnsport model for Heritage Deterioration) to Suoyang Ancient City, an archaeological site in north-west China made of rammed earth. ViSTA-HD is a cellular automata model developed by the authors to model the risk of environmentally-driven deterioration at earthen heritage sites. It is comprised of two modules: (i) an environmental module that spatially resolves environmental processes across an earthen site, and (ii) a deterioration module that spatially resolves the risk of deterioration across a wall face. The risk of deterioration is simulated for three common deterioration features at Suoyang - polishing, pitting and slurry. We use ViSTA-HD to investigate variations in deterioration risk under future potential climate scenarios across the 21^st century. We also use the model to robustly test the impact of potential nature-based conservation strategies.