Palaeolithic decorated caves are a heritage site of the highest order, whose conservation is not guaranteed solely by closing off access, but requires defined protocols to assess biological, geological and water-related risk factors. The overall objective of the project is to develop an administrative roadmap and a management tool using an intuitive database. Specific objectives include the geomorphological characterisation of natural containers, archaeological and 3D graphic documentation, and the development of colorimetric profiles to monitor structural or chromatic alterations over time.
Methodology
The research employs a multidisciplinary approach that includes:
- Environmental monitoring: Installation of HOBO devices to measure temperature and humidity, as well as advanced weather stations in Ekain that record CO2, suspended particles and air flow in real time.
- Photogrammetric monitoring: Use of Structure From Motion (SFM) techniques to obtain sub-millimetre 3D models that allow comparison of changes in the rock surface, such as exfoliation or mineral deposits.
- Colorimetric monitoring: Application of non-invasive methods using standardised colour scales and calculation of the Delta E (ΔE*ab) metric to objectively quantify pigment degradation.
Results
The work carried out between 2024 and 2025 yielded the following conclusions for each cave:
- Ekain Cave: Identified as a closed system with horizontal stratification. The Zaldei sector is the most affected due to recurrent condensation and summer CO2 peaks that promote carbonate dissolution.
- Altxerri Cave: It has high thermal stability, but humidity saturation (95-100%) increases the risk of biocolonisation and biofilm development on the decorated panels.
- Aitzbitarte Hill: It shows vertical thermal stratification; while Aitzbitarte IV is more sensitive to external changes, level IX stands out for its total thermal inertia and stability.
- Condition of the pigments: Colorimetric control confirms general stability, although the Red Panel of Aitzbitarte IV shows active degradation linked to water dynamics and surface washing.
Conclusions
The report concludes that the state of conservation of the wall art is satisfactory and stable, as the alterations detected are of natural origin and evolve at a slow pace. The main risks for the future are prolonged condensation and biocolonisation resulting from extreme humidity and poor ventilation. It is recommended to maintain seasonal CO2 monitoring, carry out periodic colorimetric monitoring and periodically review the physical closure systems to prevent alterations in the microclimate of the caves.