Spatial distribution of megalithic monuments in the subalpine belt of the Pyrenees: Interpretation and implications for understanding early landscape transformation

Using a database of all the catalogued dolmens and stone circles in six Pyrenean valleys, we investigated the distribution of these megalithic monuments on the basis of elevation, gradient, aspect, terrain ruggedness, and terrain position, and identified factors potentially explaining the distribution of the monuments. A map of the areas having the highest probabilities of occurrence of megalithic monuments was developed, and showed that megalithic monuments are located in relatively accessible areas having gentle gradients and low terrain ruggedness close to the fluvial network, with wide U-shaped glacial valleys being the preferred locations. The altitudinal distribution showed one concentration of dolmens and stone circles at relatively low elevation (1250–1400 m a.s.l.) in the mid montane belt, and another at high elevation, at approximately the level of the timberline (1750–1900 m a.s.l.) adjacent to the alpine belt. Today, both areas are pastures that have historically sustained livestock, the traditional economic basis of Pyrenean valleys. The map showing the probability of occurrence of megalithic monuments in the study area suggests that a number of potentially favorable areas were largely inaccessible or too far from the main livestock routes, and remained forested until the Middle Ages. These findings and a variety of archaeological studies contribute to propose that the first shepherds: (i) understood the altitudinal organization of mountain areas; (ii) used the best accessible flat areas in the mid montane belt in late spring and early summer; and (iii) used the upper subalpine/alpine belt in summer.