Green alder forest

On the ubac slope (i.e. the slope with the shortest exposure to sunlight), little waterfalls sourced by glaciers help maintain a forest of green alders, known locally as “arcosses”, which grow in damp, shaded environments. Their supple arched branches reach downstream while their roots are anchored upstream. In avalanche corridors they can therefore bend under the weight of the snow and then right themselves without suffering damage. This “primary” forest, so called as it has existed since the end of the Ice Age, covers almost eight kilometres and is one of the largest in Europe.