Trouble in the air at Waitomo Caves

By ELIZABETH BINNING

Scientists won't hesitate to close the Waitomo Caves if the threat of irreversible damage, caused by people breathing, becomes too great.

More than 2500 people visit the popular tourist attraction each day at this time of year and each breath they take can seriously damage the fragile limestone features.

So environmental scientist Chris de Freitas and his team are closely monitoring the caves and managing visitor access to them.

They're using a new sophisticated piece of equipment, which monitors the cave environment every 30 seconds, to ensure no unnecessary harm is done to the caves.

The Waitomo Caves, which are known worldwide for their glow-worms, tunnel systems, stalagmites and stalactites, opened to the public in 1880.

In 1979 people started noticing a big drop in glow-worm numbers so Dr de Freitas was called in study their microclimate.

Since then the Auckland University scientist and his team of colleagues have spent countless hours investigating the cave environment and the impact humans have on it.

They have discovered the presence of just a few people can dramatically change heat, humidity and moisture levels in the caves.

Carbon dioxide from people's breath gathers in the restricted cave space. If the air flow is not strong enough to carry the carbon dioxide outside, it reacts with moisture in the air and dries out the caves. This stresses the glow-worms and, over time, corrodes the limestone features which take hundreds of thousands of years to develop.

Dr de Freitas says the key to preserving the caves and keeping glow-worm numbers up is management of those carbon dioxide levels.

It means restricting access to some smaller parts of the cave where the airflow is limited and, as on December 29, closing the caves until the carbon dioxide levels drop to an acceptable level.

Monitoring the caves is not a new process, but this year an Assmann Psychrometer takes automatic readings of air flow, heat and carbon dioxide every 30 seconds.