Formed essentially of siliceous and crystalline rocks, the Aiguilles Rouges constitute a privileged observatory, facing the glaciers and the summits of the Mont-Blanc massif.
The Vallon de Bérard nature reserve is located on the northern slopes of the Aiguilles Rouges mountain range, on the right bank of the Eau de Bérard stream. It culminates at 2965 m at the Aiguille du Belvédère, and its lowest point is at 1700 m in the Vallon de Bérard. Most of the territory covers the alpine and nival levels, and is marked by the presence of small relict glaciers.
The Bérard valley is an ancient glacial cirque which still shelters four hanging glaciers whose moraines feed the slope formations, scree and rockfalls which cover the slope and the ancient glacial flat with blocks and alluvium. On these crystalline blocks and scree, a diversified flora develops.
Twenty rare or protected species have been identified, including six protected in France. The natural forest in balance with the soil, the climate and all its components is sometimes decimated by avalanches. Whether it is a spruce stand, a melezin or a cembraie, it is then replaced by vast rhododendron bushes, topped by moorland, then by alpine lawns. The green alder colonizes the avalanche corridors.
The fauna is typical of high mountain areas, with emblematic species such as the ibex, the chamois, the black grouse, the golden eagle or the tichodrome. The Bérard pass is also an important migration corridor.