Resilience of the Roman Balneum in the face of Climate Change at Brexiza, Greece: Unravelling Pathology, Advancing Risk Assessment Methodologies and Adapting Preservation Strategies.

The Eastern Mediterranean’s archaeological heritage faces intensifying hazards under climate change, including higher temperatures, aridification, humidity fluctuations, and marine influences. Focusing on the Roman balneum at Brexiza, Greece, this paper translates a presentation-driven workflow into a concise assessment that connects observed pathologies with quantified climate risks and actionable preservation steps. Building on the Heritage Hazard Index (HHI), we advance the framework with two targeted indicators—Biological Degradation and Salt Crystallization—to better represent material-specific sensitivities. The Biological Degradation Index estimates microorganism richness (D, temperature-dependent) and biomass (B, temperature–precipitation-dependent). For Brexiza, increasing aridity contributes to improved resilience, with projected relative declines of 7.75–37.75 % in D and 2–6 % in B versus a 1971–2000 baseline under RCP4.5/8.5. In contrast, humid regions with longer growing seasons may face higher biodeterioration pressure. The Salt Crystallization Index distinguishes unhydrated (NaCl) from hydrated (Na₂SO₄) systems by counting dissolution–crystallization cycles driven by RH–temperature dynamics. For Brexiza, cycles are projected to decrease by 51.08–73.23% (NaCl) and 41.28–71.38% (Na₂SO₄) relative to baseline, implying reduced salt-induced stress, even as coastal exposure remains a concern. We close with an adaptation agenda aligned to these results—prioritizing drainage and moisture control, salt-risk monitoring, and staged measures for fabric stability—plus a refinement to HHI: site-specific baseline classification, graded absolute risk scales per parameter, and joint tracking of absolute and relative risk to support comparable, decision-ready outputs.