Beech and Ash Dieback

Beech has historically thrived on the heavy clay soils of the Sundgau, forming the backbone of many communal forests. But these same soils, which retain water in wet periods, can become extremely hard and impenetrable when dry — cutting off tree roots from moisture during drought. The town of Altkirch has reported that beech, ash, and spruce are the hardest-hit species in its communal forests. The combination of repeated drought, warm winters that fail to kill off pathogens, and fungal infections has created a situation where the most common local tree species are all declining simultaneously. Foresters are harvesting weakened beech and ash preemptively — particularly along paths and roads for public safety — while trying to preserve some dead wood for biodiversity. The ONF is currently testing replacement species in the Grand Est, with oak and cedar among the leading candidates, alongside dozens of other species. But transitioning from beech-dominated forests to diverse mixed stands is a generational project, and there is still uncertainty about which species will thrive under future climate conditions on Sundgau soils specifically.