Are Nature-based Solutions for Built Heritage Conservation Resilient to Climate Change? The Response of Grass-based Soft Caps in Britain and Ireland to Future Climate Scenarios

Abstract

ABSTRACT Nature-based solutions (NbS) offer an exciting opportunity to work with nature to conserve heritage sites and objects. Soft capping is a novel form of NbS used commonly in Britain and Ireland to help conserve ruined and free-standing walls; soil and vegetation is placed on the wall head to help reduce deterioration by buffering thermal fluctuations and regulating moisture. While this conservation practice has proved cheaper and more effective at reducing deterioration than traditional hard capping, soft caps need to be resilient to future environmental changes. Previous research has shown that the sedum species commonly used in soft caps are vulnerable to climate change. Thus, following feedback from an interactive webinar with practicing heritage professionals, here we assess the climate resilience of four grass species commonly found in western Europe as possible soft-capping species: Festuca rubra (red fescue), Poa pratensis (smooth meadow-grass), Catapodium rigidum (fern-grass) and Poa annua (annual meadow-grass). We use species distribution modelling (Maxent) to assess the likelihood of species survival by mid and end century based on presence probabilities derived using three climate models (HadGEM3-GC31-LL, IPSL-CM6A-LR, and MIROC6). Results show that all four species are resilient under mid-century projections, and P. annua proved resilient under all scenarios. Therefore, using turf-based soft caps incorporating one or more of these grass species could enhance the future resilience of this conservation technique. Given the growing interest in the use of nature-based approaches to heritage conservation, our study represents an important attempt to account for and adapt to a changing climate.