The canyon carved out by the Tarn river between the Causse Méjean and the Causse de Sauveterre is known as the Gorges du Tarn. Among the highest in the Occitania region, these gorges are located in the Lozère department but are also partially visible from Aveyron. The Tarn is a 236 miles (380 km) long river, one of the main ones in France, which originates in Mont Lozère before reaching the plateaus of the Grands Causses. The tree varieties found in the riparian forest (riverbanks forest) of the Gorges du Tarn are diverse, and alder, ash, willow, and other trees dot the banks of the river. Beech trees, however, occupy an ecological niche in the area as they are less common in this almost Mediterranean climate. They, therefore, draw the moisture necessary to their survival directly from the waters of the Tarn through their roots.