Forest resilience in a changing world: A tale of three mountains

orests are a key element of mountain ecosystems around the globe. They provide crucial ecosystem services to mountain communities, contributing to rural livelihood and protecting from gravitational hazards. Mountain forests are particularly sensitive to climate change: They are slow systems that are strongly thermally limited, and the rapid pace of climate warming could cross critical thresholds. A crucial element in this regard are climate-mediated disturbances from wildfire, wind, or insect outbreaks. Here, I highlight how disturbances can both challenge and foster the resilience of mountain forests. I illustrate my points by comparing three temperate mountain forest landscapes on three continents, selected to span the full gradient of disturbance activity in temperate forests. Mountain forests are generally well adapted to cope with disturbances, but if disturbances increase beyond an annual rate of approximately 2% per year tipping points could be crossed. At the same time, climate change is particularly likely to exceed the resilience of forests that have experienced very little disturbance in the past. Across all three mountain systems subalpine forests close to the tree line emerge as being particularly sensitive to change. I conclude that climate change will substantially alter mountain forest ecosystems, with important implications for mountain communities.