Keeping Visitors Out To Keep Cave Paintings Safe
Guest post from Carmen Drahl, a C&EN's Associate Editor and Haystack blogger.
Growing up, I spent every summer in northern Spain, living in my grandmother's Oviedo flat and wandering the city and surrounding villages with distant cousins. One of my greatest regrets is never having taken the 3 hour drive to what my grandma called "las Cuevas de Altamira", the storied caves and UNESCO World Heritage Site that house some of the world's most striking examples of Paleolithic art.
The caves have been closed to visitors on and off since their discovery in the late 1870s. But they've been shuttered indefinitely since 2002, because microbial colonies encroached on the priceless scenes of bison and deer on the stone ceilings. Government officials in Cantabria, the Spanish autonomous community where the cave is situated, would like to reopen Altamira to tourists. Today, in a policy forum in the journal Science (DOI:10.1126/science.1206788), researchers led by Cesareo Saiz-Jimenez from the Spanish Council for Scientific Research (CSIC), argue that would be a bad idea. The team, which has been dealing with the microscopic invaders firsthand, says that letting visitors back into the cave's fragile ecosystem would quickly undo any good that the closure has done and could cause irreparable damage.
The Science piece is rich with detail about the single-celled interlopers that threaten Altamira's cave art. They include bacteria that make food through photosynthesis, fungi, and even corn pollen blown into the cave from farms in the outside world. The presence of the corn pollen is a telltale sign that airborne fungal spores could have settled into nooks and crannies in cave walls from the outside world as well, the CSIC researchers write. The invaders come in a panoply of colors, including yellow, gray, and white, the hue that's already besmirched some of the red pigments in the paintings.
Overview of the best preserved area of the famous Polychrome Chamber in Altamira Cave. At the end are members of the research team and micro-environmental monitoring station. © MNCN-CSIS, Spain
The scientists support their argument for keeping Altamira closed with an environmental study they conducted between 1997 and 1999, when the caves were still open but on a limited schedule. At the time the argument was that the small groups of 5 at a time allowed to visit would not perturb cave temperature, humidity, or carbon dioxide concentration, all factors that must be kept in check to prevent microbial flourishing. The team reports data from two consecutive days which suggest visitors have a negative impact on the cave environs. Visitors changed temperature and carbon dioxide concentration faster than the caves could bounce back.
The team notes that this data comes from a day during peak tour season, when weather conditions were such that air exchange between the cave and the outside world was likely to happen. Still, they're taking the stance that when it comes to conserving a cultural landmark, it is better to be safe than sorry.
The Cave's Board of Directors has called for a new working group to assess whether proper cave conservation is compatible with visits, so the caves' fate is literally and figuratively up in the air.
The recession has hurt many countries in the Eurozone, with Spain being among the hardest-hit. So it's not surprising that government officials would want to reopen a cultural crown jewel to entice tourists. Frankly, I don't think I would make a special trip to Cantabria just to visit the replica caves that have been set up for tourists. There's only so much you can do to imitate the dank yet majestic otherworldliness of the real thing. But given the limitations of preservation technology, it's a little selfish of me to want to risk destroying a landmark of Spain's cultural heritage just so my untrained eyes can gawk at it.
A wall of the Altamira Cave entrance hall where several types of microbial colonies are visible. © Science 2011