Quantifying the impact of human visitation in two cave chambers on Mona Island (Puerto Rico): Implications for archaeological site conservation

Recent archaeological research has discovered well preserved historic and pre-Columbian art covering numerous walls inside caves on Mona Island. Human visits can pose a serious threat to the long term conservation of these fragile engravings and paintings by increasing condensation corrosion rates. The quantification of environmental changes to caves related to human visitation is relevant for prediction of condensation corrosion processes and cave site management policies. This study addresses the threat of increased condensation corrosion to cave art. Data collected in two caves show changes in cave air temperature (T), relative humidity (RH) and CO2 partial pressure (pCO2) caused by visitation. Based on the environmental observations, cave air exchange times and condensation corrosion rates of different visitor group sizes were quantified. The corrosion rates increase with the number of visitors and also depend on the chamber ventilation characteristics. Periods of visitation might be the only times when condensation corrosion can occur, especially in cave chambers distant from the cave entrance. This evidence points out the need to develop a conservation management plan that takes account of visitation levels to ensure preservation for future generations.