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American Association for the Advancement of Science

If you love something, close it up? The weird world of caves

In the center of this image you can see the famous deer present in the painted ceiling of Polychrome Hall. In the lower left are the temperature, humidity and wind speed sensors located a few inches from the ceiling to detect any changes in the microclimate.
[Image MNCN-CSIS, Spain]

How would you feel if someone told you they'd discovered someplace amazing, but if other people came to visit, it would be ruined? Would you wonder, what's the point of protecting it, if nobody can enjoy it? Or, could you appreciate the place without having to actually see it in person?

This is a dilemma faced by people interested in caves, particularly the ones that hold rare and delicate wonders inside. These treasures might be beautiful mineral formations, like stalactites and stalagmites, or they might be prehistoric wall paintings, such as the images of wild animals and human handprints at Altamira Cave in Spain.

Unfortunately, tourists were loving Spain's Altamira Cave and its amazing artwork to death before it was closed to the public in 2002. Caves are such delicate places, often very separate from the surface world, that people can damage them by simply walking through. Our bodies can change the temperature of the cave and the chemistry of the air. Tiny organisms can hitch a ride in on our clothes and shoes. Also, when people visit caves they need light, which is a radical change for most caves. At Altamira, microbes that don't naturally grow in the cave started to colonize the paintings.

Closing the cave to the public helped stop the growth on the paintings. Recently, the managers of this unusual site have been under pressure to reopen the cave so that people can visit it.

But, reopening Altamira Cave would be a big mistake, say a team of Spanish scientists writing in the 7 October 2011 issue of the journal Science. Cesareo Saiz-Jimenez of IRNAS-CSIC and his colleagues explain in a Policy Forum that they've studied the impact of visitors on the cave and gathered data from hundreds of visits monitored between 1996 and 1999.

If the cave reopens to the public now, they say, it will lead to increases in temperature, humidity and carbon dioxide, thus reactivating condensation and rock corrosion. Ultimately, if the cave is not protected, its resources could be lost forever.