Natural processes in the degradation of open-air rock-art sites: an urgency intervention scale to inform conservation.

Abstract

Open-air rock-art forms one of the most widely distributed categories of prehistoric material culture with examples recognized across the Old and New Worlds. It is also one of the most threatened features of human heritage and is susceptible to accelerated decay as a result of anthropogenic and natural processes. Much attention has previously been given to the impact of identifiably human activities and their mitigation, but the aim of this research is to redress the balance and focus on understanding the short-, medium-, and long-term impacts of natural processes. The main objectives of research are to identify open-air rock-art natural degradation causes, create a suitable method to assess the state of conservation of any given engraved outcrop of the Côa Valley rock-art complex and develop a urgency scale for conservation interventions. The urgency scale will be established by thoroughly examining a sample of the most – in terms of conservation – representative engraved outcrops. Since more than one thousand outcrops with rock-art still subsist today, it would be impossible to examine them all. Therefore, a sample comprising outcrops that possess most, if not all, of the variables that might affect stability and conservation state will be chosen. Some of the issues to consider are weathering and erosion of outcrops, or slope gradient and aspect of the hills where these are located. Such phenomena as biological colonization, rainwater percolation or chemical exchanges at surface level will also be analyzed. The expected end result of research is the creation of a method to determine the condition of outcrops and to identify methodically those in most urgent need of conservation. As a result, informed conservation action plans can be systematically tailored to suit specific natural conditions. Moreover, conservation interventions can be prioritized within a total universe of 1000 outcrops with rock-art.