Unintentional effects of light in the Carlsbad caves


Since I’m used to almost every place so people can see their way, I haven’t paid much attention to lighting the greatest natural underground wonders in the United States. My first trip through the great room of the Carlsbad Caves was on Thanksgiving. We arrived soon after this amazing natural wonder opened to the public. With so few people there, we could share a trail in the Great Room of the Carlsbad Caves to ourselves for a few minutes.

It took us a few minutes for our eyes to adjust, especially to my escort who needed cataract surgery in a few months. The lighting was dim. In some places there seemed to be lights at one point that were now either on or off. Where we could see, we stood in awe at the incredible natural growths that hung from the ceiling or emerged from the ground.

Since most people at home were getting ready to eat Thanksgiving, we were able to have long conversations with the various park rangers who walked this wide underground wonderland. One of our questions was about lighting.

Ranger told us that the lighting setup was designed by a theater expert. There used to be much bigger and brighter lights spreading across the Great Room. After some time, an unintended consequence was noted. Green algae began to appear on the walls. That hadn’t happened before because the Carlsbad Caverns had turned black, before people wanted to see what was inside. Earlier explorers came down either with oil lamps or with lamps on solid hats worn by the miners. They did not lead to algae growth.

To prevent the growth of green on the damp walls of Carlsbad Cave, some light bulbs were turned off and the intensity of others was reduced. While this reduced algae growth, it also reduced what you can see. If we had imagined it, we would have brought a high-intensity lamp. This is strongly suggested on some of the water tours where the trails are completely dark.

In the next few years, the park service will install LED lighting. They do not encourage algae growth and will last longer than what is there now. The park ranger explained that many more natural wonders will be seen and that the LED will allow Carlsbad Caverns to remain in its more natural state … if you dismiss the fact that “natural” means resin black.