Anthropogenic impacts on the Glowworm Cave, Waitomo, New Zealand: a microclimate management approach

Waitomo Glowworm Cave is a highly visited cave where the highlight is viewing the bioluminescence display of a large colony of glowworms. The visitation levels result in the build-up of anthropogenic CO2, to the extent that it could cause corrosion of speleothems. The cave experiences chimney-effect ventilation with air flowing either upward or downward through the main cave chambers depending on air density differences between the cave and the outside environment. Lack of airflow leads to CO2 build-up; however, unrestricted airflow can draw in cool, dry air which is harmful to the glowworms. Consequently, airflow is managed by controlling the opening and closing of a door that seals the upper-most entrance, preventing ventilation under drying conditions and promoting ventilation when it is necessary to clear CO2 and when inflowing air has high relative humidity. A network of microclimate sensors in the cave allows prediction and management of the ventilation pattern. Management leads to asymmetric airflow through the year, which has a flow-on effect on cave temperature. Microclimate monitoring supports the current management practices that use door control to enhance cave ventilation when people are in the cave. Suppressing airflow, especially in winter, reduces the introduction of dry air.