Humanity lavishes billions of dollars annually on its art objects, art repositories, and art industry. By comparison, its endeavors to look after its oldest and most valuable art treasures are miniscule. Despite its appearance of relative robustness, rock art is quite fragile, and what we see today is only the tiny surviving fraction of what was once created. Two factors need to be distinguished in the deterioration of rock art: the effects of natural processes, and the damage occasioned by human agency. The mitigation of the former is often difficult, whereas that of anthropic destruction is in most cases easily achievable. Importantly, deterioration by humanly introduced factors far outweighs natural degradation. In understanding the interplay between these two factors it is important to appreciate that the rock art that exists today does so because it has survived a great many natural decay processes, often surviving in a state of relative equilibrium with its ambient environment. Hence, it is likely to persist much longer unless there is a significant change in its preservation conditions, especially one introduced by human intervention. This may be as simple as the introduction of human visitation to a formerly pristine site, or as complex as the occurrence of acid rain caused by industrialization.
The principal natural agent of rock art loss is moisture, mainly in the form of rainwater, capillary moisture in porous rock, condensation in caves and shelters, freeze-and-thaw cycles, surface run-off, and secondary effects such as salt efflorescence or exfoliation. Physical weathering of rock art panels occurs as insolation (solar radiation), lightning strikes, brush-fires, Kernsprung, tectonic adjustments, and kinetic damage (aeolian, gravity, or water induced). Many forms of biological factors can contribute to weathering, including bacteria, fungi, lichens, algae, mosses, larger plants, insects (mud-daubing wasps, termites, bees), nesting birds, and various larger animals, especially domestic and feral species. For many of these threats, protective measures have been found. Site hydrology, for instance, can be controlled by artificial silicone driplines in shelters; condensation can be eliminated by climate control.
One animal, however, is causing far greater rock art destruction than all other factors taken together. Of the many forms of damage occasioned by humans the perhaps most repulsive is that occasioned by researchers, be it through misguided recording activities or through their role in permitting or condoning the destruction of rock art by industrial or infrastructure development. The former has been largely eliminated in recent decades, but the latter continues unabated. At one Australian site complex alone, at Dampier, it has been responsible for the obliteration of about 100 000 petroglyphs. Tourists and site visitors contribute to rock art deterioration, though it has often been found necessary to sacrifice some sites to them in order to preserve many others. The locations of new sites are no longer made public, and well-known pristine sites such as Chauvet, Cussac, and Cosquer Caves in France are totally closed to all, except a few researchers who only enter these sites with careful precautions to prevent contamination. For instance, researchers are not allowed to walk on the floor of Chauvet Cave. In Australia, most of the cave art sites are only accessible to two or three researchers and their locations are generally confidential.
There are very few professional rock art conservators worldwide, and the standards they apply vary from one region to another. Their tasks include graffiti removal, moisture and climate monitoring and control, and the design of site management measures. The latter differ according to local circumstances, and include such measures as the erection of fences to keep out animals, the installation of visitor boardwalks and paths, and in some regions protective grilles. In modern site management practice, the concept of ‘site fabric’ is paramount, referring to all physical and nonphysical aspects of a place, including accretionary deposits on the rock, even its ambience or religious significance. The primary principle of intervention at a rock art site is that any modifications must be fully reversible. Today’s site conservation and management practices may well be superseded tomorrow, and the cultural resource in question is, after all, not renewable.