Highlights
- COVID-19 restrictions created a natural experiment in cave tourism
- Regular tours generated a detectable high-frequency thermal signature
- Thermal disturbances propagated throughout interconnected cave airspaces
- Tour scheduling governed visitor-induced thermal signal emergence
- Frequency-domain analysis revealed hidden anthropogenic signals
Abstract
Tourist activity is widely recognised as a source of cave microclimate disturbance, yet visitor-induced variability is difficult to distinguish from natural environmental fluctuations. The coronavirus pandemic created a natural experiment at Poole’s Cavern, United Kingdom, in which periods of complete closure could be compared with contrasting visitor access regimes. Two years of high resolution temperature records from six monitoring points were analysed. Harmonic regression and a state space model removed deterministic diurnal cycles and lower frequency temperature variability. The remaining residual variability differed systematically among visitor access regimes and between daytime and nighttime conditions. Spectral analysis of the residuals identified a recurrent oscillation centred on 48 cycles per day, the frequency of guided tours departing every 30 minutes. This oscillation formed no distinct spectral peak during pre-pandemic tourism, when tours ran on demand, but emerged consistently when tours ran to a fixed schedule. Whether visitor-induced thermal forcing can be detected therefore depends on how regularly visits are organised in time. The signal was present throughout the cave, from monitoring points near the entrance passage to locations beyond the principal tourist route. Reconstructed by inverse Fourier transformation, the 45.5–50.5 cycles per day band accounted for up to half of the daytime residual temperature variability at some monitoring points. Scheduled cave tourism can thus impose a distinct thermal signature on cave microclimates that conventional analyses of mean temperature do not detect. More broadly, the study shows how high resolution monitoring and frequency domain analysis can reveal subtle anthropogenic forcing within complex cave microclimate records.
DOI
https://doi.org/10.5038/1827-806X.ijs2630
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.
Recommended Citation
Rowberry, M., Gunn, J., Smith, A., 2026. Hidden thermal signatures reveal the microclimatic influence of scheduled cave tourism. International Journal of Speleology, 55(3), ijs2630. https://doi.org/10.5038/1827-806X.ijs2630
