7 OCTOBER 2011 VOL 334 SCIENCE www.sciencemag.org 42

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

CONSERVATION

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

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

In the last decade, considerable atten-tion has been paid to the deteriora-tion of the caves that house the world’s

most prominent Paleolithic rock art. This is exemplified by the caves of Lascaux (Dor-dogne, France) (1) and Altamira (Canta-bria, Spain), both declared World Heritage Sites. The Altamira Cave has been closed to visitors since 2002. Since 2010, reopen-ing the Altamira Cave has been under con-sideration. 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 paint-ings after decades of visits (e.g., 175,000 visitors in 1973). In 1978, the Spanish gov-ernment 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 sur-vey, 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 Septem-ber 2002, Altamira had to be closed to the public because of the presence of photo-trophic 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 microorgan-isms 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.

Harmful Impacts of VisitorsThe current status of the cave is the result of the accumulation of multiple microenviron-mental 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) environ-ment with very little connection to the out-side atmosphere. The numerous condition-ing 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 Poly-chrome 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 infiltra-tion, precipitation of speleothems (mineral deposits) and exchange with the external atmosphere; and the maintenance of very sta-ble microenvironmental conditions because of limited airflow in the Polychrome Hall.

The Spanish National Resource Council (Consejo Superior de Investigaciones Cientí-ficas, CSIC) studied the cave between 1996 and 1999. The studies focused on determin-ing the impact of visitors on the micro-envi-ronmental 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 cor-rosion caused by visitors under the 1982 visi-tation 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 activ-ity reduced to a minimum. Cañaveras et al. (8) predicted that in the event of a change in the lighting conditions—such as perma-nent 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. Thereaf-ter, 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 micro-environmental and geochemical characteris-tics 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 envi-ronmental, geochemical, hydrological, and microbiological data put at the disposal of the Ministry of Culture.

Progress, but Persistent ProblemsThe 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 sys-tem, 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 Las-caux, where chemical products and antibiot-ics were used (1). However, in Altamira the conservation problems are still far from being solved. Evidence of microbial colonies con-sisting 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 imple-mented in recent years was depriving the eco-system of carbon in order to inhibit bacterial growth and to reduce exchange between the cave atmosphere and exterior.

1Institute for Natural Resources and Agrobiology, Spanish National Research Council (IRNAS-CSIC), 41012 Sevilla, Spain. 2Universidad de Alicante, 03080 Alicante, Spain. 3National Museum of Natural Sciences, Spanish National Resource Council (MNCN-CSIC), 28006 Madrid, Spain.

*Author for correspondence. E-Mail: saiz@irnase.csic.es

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Our team has modeled the impact of visitors on the cave and gathered data from hundreds of visits monitored between 1996 and 1999 (fig. S5). If the cave reopens to the pub-lic, continued entry of visi-tors would cause increases in temperature, humidity, and CO2 in Polychrome Hall, reactivating conden-sation and host-rock corro-sion (3). Air warming and the inevitable turbulence caused by visitors favor an air exchange between Poly-chrome Hall and areas clos-est to the entrance, where there are microbial coloni-zations on walls and ceil-ings (10) (see the figure). In addition, visitors walk-ing will cause f ine par-ticle resuspension from ground sediments. Air cur-rents caused by visitors will erode wall and sedi-ment surfaces, provoking microparticle detachment (releasing bacterial and fungal spores). Additionally, new nutrient sources will be supplied to the ecosystem by tourists and guides. This could lead to a new stage of proliferation of microorganisms whose current trend appears to be moving toward a stationary state.

In addition to bacterial colonization, fungi have been observed in Altamira Cave (11, 12), as in Lascaux (fig. S4 and table S1). These fungi have three well-defined origins: plant saprophytes introduced from the exterior, entomopathogenic fungi intro-duced by arthropoda, and coprophilous fungi growing on rodent feces (fig. S4A). In 2007, the scientific instruments control-ling cave environment were repeatedly col-onized by fungi (fig. S4B) after an archae-ological excavation was carried out within the cave in October 2006, despite the rec-ommendations of CSIC. Periodic cleanings of instruments were required using envi-ronmentally friendly methods and com-pounds. For example, periodic mechanical removal of the ground sediments adjacent to the instruments, which were colonized by fungi, and treatment with hydrogen perox-ide. Biocides have not been used because the experience of Lascaux showed that ben-zalkonium chloride applied between 2001 and 2004 is being used by microorganisms as a carbon and nitrogen source (1).

Politics and UncertaintySince 2010, reopening the cave to visi-tors has been seriously considered, with the belief that this will boost the local tour-ism economy (13). In December 2010, the Board of Directors of the cave called for a new international scientific commission to prepare a report deciding whether cave con-servation is compatible with visits.

Although our recommendations, based on data collected over the past 15 years, do not support reopening of the cave, as sci-entists, we are in favor of the possibility of evaluating our data with other special-ists. We are hopeful that the international scientific commission to be appointed by the Board of Directors, which has declared that this cave is one of the best scientifically studied in the world (14), will consider the data we have collected.

Tourist visits to many caves and other subterranean sites should be looked upon as a potential risk for the conservation of cultural heritage. Archaeologists, environ-mentalists, and microbiologists agree on the beneficial effect of closing subterranean sites for their conservation, as shown by the recent announcement that some Egyp-tian tombs including Tutankhamun’s will be closed to visits, with the tourists rerouted to a replica (15). Altamira Cave, although cur-rently closed, is at real risk. Whether or not this cave follows the dangerous path of Las-

caux Cave with continued fungal outbreaks is in the hands of the Ministry of Culture to keep the cave closed to visits.

References 1. F. Bastian, V. Jurado, A. Nováková, C. Alabouvette,

C. Saiz-Jimenez, Microbiology 156, 644 (2010). 2. J. A. Lasheras, C. de las Heras, Coalition 12, 7 (2006);

www.rtphc.csic.es/PDF/NL12.pdf. 3. S. Sánchez-Moral et al., Sci. Total Environ. 243-244, 67

(1999). 4. Museum of Altamira, http://museodealtamira.mcu.es/

ingles/historia_museo.html. 5. C. Holden, Science 297, 47 (2002). 6. C. Schabereiter-Gurtner, C. Saiz-Jimenez, G. Piñar, W.

Lubitz, S. Rölleke, FEMS Microbiol. Lett. 211, 7 (2002). 7. E. Villar et al., in Estudios Físico-Químicos de la Sala

de Polícromos. Influencia de la Presencia Humana y Criterios de Conservación (Ministerio de Cultura, Madrid, 1984), pp. 95–110.

8. J. C. Cañaveras, S. Sanchez-Moral, V. Soler, C. Saiz-Jimenez, Geomicrobiol. J. 18, 223 (2001).

9. S. Sanchez-Moral et al., in Redescubrir Altamira (Grupo Santander, Madrid, 2002), pp. 245–257.

10. S. Cuezva, S. Sanchez-Moral, C. Saiz-Jimenez, J. C. Cañaveras, Int. J. Speleol. 38, 83 (2009).

11. V. Jurado et al., Naturwissenschaften 96, 1027 (2009). 12. E. Porca et al., Ecol. Indic. 11, 1594 (2011). 13. T. Constenla, El Pais, 21 December 2010,

www.elpais.com/articulo/english/The/prehistoric/art/that/won/t/be/seen/elpepueng/20101221elpeng_4/Ten.

14. Ministry of Culture, Spain, www.mcu.es/archivoswebmcu/gabineteprensa/notas/23952010/altamira.pdf.

15. M. Pitts, The Guardian, 17 January 2011, p. G2; www.guardian.co.uk/culture/2011/jan/17/tutankhamun-tomb-to-close.

Supporting Online Materialwww.sciencemag.org/cgi/content/full/334/6052/42/DC1

10.1126/science.1206788

1st door (entrance)

2nd door Polychrome Hall

Microbial colonies

Microenvironmentalmonitoring system

Conduit through the wall

N

0 5 10

Meters

Conduit through the wall

Corridor

Crossing

Yellow coloniesGray coloniesWhite coloniesCyanobacteria

Entrance Hall

Spatial distribution of the visible microbial colonies on the ceiling at Altamira Cave. The Polychrome Hall features dozens of paintings of bison, deer, and other animals, spread across 150 square meters of cave ceiling that were painted more than 14,000 years ago. [Figure modified from (10)]