POLICYFORUM CONSERVATION

Paleolithic Art in Peril: Policy and Science Collide at Altamira Cave

Despite evidence of damaging human impacts, cave paintings may again be threatened if visitors are allowed access.

I

n the last decade, considerable attention has been paid to the deterioration of the caves that house the world’s most prominent Paleolithic rock art. This is exemplified by the caves of Lascaux (Dordogne, France) (1) and Altamira (Cantabria, Spain), both declared World Heritage Sites. The Altamira Cave has been closed to visitors since 2002. Since 2010, reopening the Altamira Cave has been under consideration. We argue that research indicates the need to preserve the cave by keeping it closed in the near future. In the 1970s, Altamira Cave sparked a political dispute between local and regional administrations and the state and received a great deal of public attention. In October 1977, Altamira had to be closed to the public because of severe deterioration of the paintings after decades of visits (e.g., 175,000 visitors in 1973). In 1978, the Spanish government took over ownership of the cave, which today belongs to the Spanish Ministry of Culture and is managed by the National Museum of Altamira (2). In 1982, after a microclimatic survey, Altamira reopened to the public with a limit of 11,000 people per year (3) or, in another document, 8500 visitors per year, excluding guides (4). However, in September 2002, Altamira had to be closed to the public because of the presence of phototrophic microorganisms on the paintings (5) (see the figure and fig. S1), a phenomenon similar to that suffered by Lascaux 50 years before. Colonization by these microorganisms was a consequence of decades of use of artificial lighting in the famous Polychrome Hall and was accompanied by development of white microbial colonizations directly on the red paintings (6) (see the figure and fig. S3). This showed that Altamira Cave might be mimicking the deterioration processes at Lascaux. Institute for Natural Resources and Agrobiology, Spanish National Research Council (IRNAS-CSIC), 41012 Sevilla, Spain. 2Universidad de Alicante, 03080 Alicante, Spain. 3 National Museum of Natural Sciences, Spanish National Research Council (MNCN-CSIC), 28006 Madrid, Spain. 1

*Author for correspondence. E-Mail: [email protected]

42

Harmful Impacts of Visitors

The current status of the cave is the result of the accumulation of multiple microenvironmental changes and impacts suffered from the time of its discovery in 1879 (2) (figs. S1 to S6). In its natural state, the cave should be an oligotrophic (nutrient-poor) environment with very little connection to the outside atmosphere. The numerous conditioning projects, changes in the top soil and cave sediments, archaeological digs, and massive amounts of visitors transformed the pristine ecosystem into one with an abundance of available nutrients. Preservation of a large part of the Polychrome Hall ceiling paintings from their creation more than 14,000 years ago until their discovery was aided by several factors: absence of light; low rates of water infiltration, precipitation of speleothems (mineral deposits) and exchange with the external atmosphere; and the maintenance of very stable microenvironmental conditions because of limited airflow in the Polychrome Hall. The Spanish National Resource Council (Consejo Superior de Investigaciones Científicas, CSIC) studied the cave between 1996 and 1999. The studies focused on determining the impact of visitors on the micro-environmental conditions of the Polychrome Hall and highlighted the need to revise the criteria used by the University of Cantabria to design the 1982 visitation schedule (7) because deterioration processes had not stopped. Sanchez-Moral et al. (3) concluded that corrosion caused by visitors under the 1982 visitation schedule would be up to 78 times that arising from natural processes. Phototrophic microorganisms were observed in 2000 in the Polychrome Hall, as resting forms or with their metabolic activity reduced to a minimum. Cañaveras et al. (8) predicted that in the event of a change in the lighting conditions—such as permanent or extensive lighting, as subsequently occurred—growth of these communities would take place. This did indeed occur in 2002 (fig. S1A) and led to the second cave closure. Once the cave was closed in 2002, the Ministry of Culture appointed the CSIC team

to survey and control the cave from 2003 to 2005 and from 2007 to 2009. Thereafter, CSIC is controlling cave microclimate through successive contracts, the last ending on March 2012. Research focused on the cave as an ecosystem dependent both on microenvironmental and geochemical characteristics of the underground environment and an energy-matter exchange with the external atmosphere. The conclusions of the research were against the reopening of the cave to visitors (9–11). This was supported by environmental, geochemical, hydrological, and microbiological data put at the disposal of the Ministry of Culture. Progress, but Persistent Problems

The 2002 closing represented a clear benefit for conservation of the paintings: The green phototrophic colonizations did not continue to progress; however, small patches are still evident (fig. S1B), and the corrosion rate of the paintings’ host rock decreased. A decrease was also noted in the content of organic matter and nitrogen compounds in the infiltration waters after the elimination of cattle activities in the land above the cave and regular mowing and removal of grasses. Installation of a new access door in 2007, equipped with a thermal insulation system, followed 20 m after by a second door, reduced the entry of airborne particles, the condensation rate in the entrance area, and the metabolic activity of the main visible microbial colonies (10–12) [see supporting online material (SOM)]. These preventive conservation actions were quite different from steps taken in Lascaux, where chemical products and antibiotics were used (1). However, in Altamira the conservation problems are still far from being solved. Evidence of microbial colonies consisting of different-colored patches are mainly located in the area near the cave entrance (fig. S2) but have already reached the Polychrome Hall (10) (see the figure and fig. S3). The objective of the corrective measures implemented in recent years was depriving the ecosystem of carbon in order to inhibit bacterial growth and to reduce exchange between the cave atmosphere and exterior.

7 OCTOBER 2011 VOL 334 SCIENCE www.sciencemag.org Published by AAAS

Downloaded from www.sciencemag.org on October 7, 2011

Cesareo Saiz-Jimenez,1* Soledad Cuezva,2 Valme Jurado,1 Angel Fernandez-Cortes,3 Estefania Porca,1 David Benavente,2 Juan C. Cañaveras,2 Sergio Sanchez-Moral3

POLICYFORUM

www.sciencemag.org SCIENCE VOL 334 7 OCTOBER 2011 Published by AAAS

Downloaded from www.sciencemag.org on October 7, 2011

1st door (entrance) Our team has modeled the impact of visitors on the cave and gathered data Microbial colonies from hundreds of visits Yellow colonies monitored between 1996 Gray colonies and 1999 (fig. S5). If the White colonies Cyanobacteria cave reopens to the public, continued entry of visiMicroenvironmental monitoring system tors would cause increases in temperature, humidity, and CO 2 in Polychrome Entrance Hall Hall, reactivating condensation and host-rock corrosion (3). Air warming and Polychrome Hall 2nd door the inevitable turbulence caused by visitors favor an air exchange between Poly- Conduit through the wall Corridor chrome Hall and areas closest to the entrance, where N there are microbial colonizations on walls and ceilings (10) (see the figure). 0 5 10 Crossing In addition, visitors walkConduit through the wall Meters ing will cause f ine particle resuspension from Spatial distribution of the visible microbial colonies on the ceiling at Altamira Cave. The Polychrome Hall features ground sediments. Air cur- dozens of paintings of bison, deer, and other animals, spread across 150 square meters of cave ceiling that were painted more rents caused by visitors than 14,000 years ago. [Figure modified from (10)] will erode wall and sediment surfaces, provoking microparticle Politics and Uncertainty caux Cave with continued fungal outbreaks detachment (releasing bacterial and fungal Since 2010, reopening the cave to visi- is in the hands of the Ministry of Culture to spores). Additionally, new nutrient sources tors has been seriously considered, with keep the cave closed to visits. will be supplied to the ecosystem by tourists the belief that this will boost the local tourReferences and guides. This could lead to a new stage ism economy (13). In December 2010, the 1. F. Bastian, V. Jurado, A. Nováková, C. Alabouvette, of proliferation of microorganisms whose Board of Directors of the cave called for a C. Saiz-Jimenez, Microbiology 156, 644 (2010). 2. J. A. Lasheras, C. de las Heras, Coalition 12, 7 (2006); current trend appears to be moving toward new international scientific commission to www.rtphc.csic.es/PDF/NL12.pdf. a stationary state. prepare a report deciding whether cave con3. S. Sánchez-Moral et al., Sci. Total Environ. 243-244, 67 In addition to bacterial colonization, servation is compatible with visits. (1999). 4. Museum of Altamira, http://museodealtamira.mcu.es/ fungi have been observed in Altamira Cave Although our recommendations, based ingles/historia_museo.html. (11, 12), as in Lascaux (fig. S4 and table on data collected over the past 15 years, do 5. C. Holden, Science 297, 47 (2002). S1). These fungi have three well-defined not support reopening of the cave, as sci6. C. Schabereiter-Gurtner, C. Saiz-Jimenez, G. Piñar, W. Lubitz, S. Rölleke, FEMS Microbiol. Lett. 211, 7 (2002). origins: plant saprophytes introduced from entists, we are in favor of the possibility 7. E. Villar et al., in Estudios Físico-Químicos de la Sala the exterior, entomopathogenic fungi intro- of evaluating our data with other specialde Polícromos. Influencia de la Presencia Humana duced by arthropoda, and coprophilous ists. We are hopeful that the international y Criterios de Conservación (Ministerio de Cultura, Madrid, 1984), pp. 95–110. fungi growing on rodent feces (fig. S4A). scientific commission to be appointed by 8. J. C. Cañaveras, S. Sanchez-Moral, V. Soler, C. Saiz-Jimenez, In 2007, the scientific instruments control- the Board of Directors, which has declared Geomicrobiol. J. 18, 223 (2001). ling cave environment were repeatedly col- that this cave is one of the best scientifically 9. S. Sanchez-Moral et al., in Redescubrir Altamira (Grupo Santander, Madrid, 2002), pp. 245–257. onized by fungi (fig. S4B) after an archae- studied in the world (14), will consider the 10. S. Cuezva, S. Sanchez-Moral, C. Saiz-Jimenez, J. C. ological excavation was carried out within data we have collected. Cañaveras, Int. J. Speleol. 38, 83 (2009). the cave in October 2006, despite the recTourist visits to many caves and other 11. V. Jurado et al., Naturwissenschaften 96, 1027 (2009). ommendations of CSIC. Periodic cleanings subterranean sites should be looked upon 12. E. Porca et al., Ecol. Indic. 11, 1594 (2011). T. Constenla, El Pais, 21 December 2010, of instruments were required using envi- as a potential risk for the conservation of 13. www.elpais.com/articulo/english/The/prehistoric/art/that/ ronmentally friendly methods and com- cultural heritage. Archaeologists, environwon/t/be/seen/elpepueng/20101221elpeng_4/Ten. pounds. For example, periodic mechanical mentalists, and microbiologists agree on 14. Ministry of Culture, Spain, www.mcu.es/ archivoswebmcu/gabineteprensa/notas/23952010/ removal of the ground sediments adjacent the beneficial effect of closing subterranean altamira.pdf. to the instruments, which were colonized by sites for their conservation, as shown by 15. M. Pitts, The Guardian, 17 January 2011, p. G2; www.guardian.co.uk/culture/2011/jan/17/tutankhamunfungi, and treatment with hydrogen perox- the recent announcement that some Egyptomb-to-close. ide. Biocides have not been used because tian tombs including Tutankhamun’s will be the experience of Lascaux showed that ben- closed to visits, with the tourists rerouted to Supporting Online Material zalkonium chloride applied between 2001 a replica (15). Altamira Cave, although cur- www.sciencemag.org/cgi/content/full/334/6052/42/DC1 and 2004 is being used by microorganisms rently closed, is at real risk. Whether or not 10.1126/science.1206788 as a carbon and nitrogen source (1). this cave follows the dangerous path of Las-

43