Most of the previous ANDYSEZs have been applicable to cave guides, cave area rangers and cavers - this one is directed to those who put lights in caves. The brilliant physicist Stephen J. Hawking has recently published a "best seller" on the nature of time. I wish somebody had done the same on light so I could pinch their good ideas and analogies.

What follows is a brief story on light and lampenflora. What the hell is it and what the hell it does sound like an awfully technical issue for this Newsletter but as usual there are some simple concepts and ideas which we need to consider before we put lights in caves. All of that is really in the next ANDYSEZ. This ANDYSEZ sets the scene by frightening you show cave managers.

The French talk about "la maladie verte" (the green sickness); the Germans use the term "lampenflora" (lamp plants). We all worry about a variety of plants - algae, slimes, molds, mosses and ferns whose colours contaminate our speleothems with black to green to light-lemon ghastliness. They range from single-celled organisms to the higher plants. The terms all refer to plants growing within caves stimulated by the light we provide so that tourists can have a "within-cave experience". We appear to have adopted lampenflora as an industry standard - this provides no problems - but the term does not imply the urgency of the French "green sickness".

When we light a cave we cannot avoid the problem of plant growth. Guy Cox (1976) describes photosynthesising (green) cave dwelling plants at levels of light below those we humans cannot detect. He talks about single-celled plants growing at levels as low as 0.002 lux producing a green tinge on the walls of Hemmings Cave at Jenolan. That is about one ten thousandth (0.0001) the amount of light Neil Kell thinks is adequate for safe pathway illumination.

We had obvious lampenflora in Glory Cave at Yarrangobilly Caves in 1982. For other reasons we closed the caves for eight months - no reduction in lampenflora was (subjectively) observed over this time period. One would have thought from first principles that the green colouration would have died away toward black - but this did not appear to be the case.

Again at Yarrangobilly, the Jillabenan has no more than 200-300 hours of illumination each year - but it does have a small scale lampenflora problem. Waitomo was just about into chainsaws to control their plant growth problems many years ago. Many (probably all) other show cave areas have this problem - I won't embarrass anyone else by using them as an example - although I could! Plant growth is an inevitable consequence of lighting.

La maladie verte or lampenflora is a disaster! Adjusting the quality and quantity of lighting can make an enormous difference but it will not remove the problem. The problem with lampenflora is that it cannot be cured - it can be slowed (by reducing light) or reduced (by using biocides or mechanical agents). Any methods that have been suggested in Australasia or further afield do not do anything more than that. That is, they do not cure the disease, but only address some of the symptoms.

I have carried out some measurements at Yarrangobilly, Buchan, Wee Jasper and Jenolan looking at existing light levels and the visual presence/absence of lampenflora (that is, whether I can see plant growth with my failing eyesight). What I did was to wander round various caves and look for plant growth. I took my trusty Gossen Lunasix 3 Light Meter; placed the base of it against the sickness, pressed the button and determined the incident light level on various surfaces. The light level can be expressed in different ways. What I did find was that there was no easily discernible plant growth at incident light levels below 3 foot candles, 30 lux, 3.5 EV, (or f8 at six seconds (at 100 ASA) if you have a camera that can measure and record light values).

This array of measurement units is not used in an effort to confuse but to allow you to use your friendly local photographer's light measurement gear to see if you are going to have problems - or to confirm that the green slime on your formations really is lampenflora - it is and it is problem.

As mentioned above the next ANDYSEZ is going to discuss what light is and the relationships between light quality (what sort of light bulbs/tubes you use), light quantity (how bright and close they are to speleothems) and la maladie verte. (If anyone has any quantitative data on this I would be delighted to have it to include in the upcoming review.)