The Côa Valley in north-eastern Portugal is one of the most significant prehistoric open-air rock art sites in the world. The majority of engraved motifs has reliably been dated to the Upper Palaeolithic, although imagery from the Neolithic, Iron Age, historical and contemporary periods have also been identified. Most of the outcrops which contain rock art motifs are located in an area of schist bedrock, scattered along both banks of the final 17km of the river Côa and positioned at the foot of sharply inclined hills.
     The Côa Valley will become a 'live' laboratory where pioneering but reliable direct conservation interventions on vertical schist outcrops can be developed and tested together with methods to monitor systematically the evolution of weathering processes. So far we have been developing a conservation programme for the Côa Valley rock art that set the bases for such monitoring and conservation work. Among the actions already implemented, we should highlight pilot conservation interventions in un-engraved outcrops with weathering and erosion dynamics at work similar to those affecting the engraved ones. These experiments were designed to test the applicability and aging of conservation materials and techniques that might be used in the future to confer stability to fragile rock art outcrops and panels.
     It is indeed vital to devise a suitable method to assess the state of conservation of any given engraved outcrop and to develop priorities for conservation interventions. Some of the issues to consider are weathering and erosion of outcrops with rock art, or slope gradient and aspect of the hills where these are located. Such phenomena as biological colonisation, rainwater percolation or chemical exchanges at surface level will also be analysed. The goals of the new research is to create a tool kit adapted to determining the condition of outcrops and to identify systematically those in most urgent need of conservation. Interventions could then be prioritised within a total universe of 1000 outcrops with rock art.
     If this invaluable heritage is to be entrusted in the best possible condition to future generations, it is essential to implement well-planned conservation work that makes the most of the limited available resources. Furthermore, it is reasonable to expect that the outcome of this project may also be of use to conservators and managers elsewhere, thus broadening existing knowledge of open-air rock art conservation.

Source: Antiquity (March 2009)