Regional Mountain Conference

Mountain forests can lower the frequency, magnitude, and intensity of gravity-driven natural hazards such as snow avalanches and rockfall, thereby protecting people, infrastructure, and livelihoods. These so-called protective forests constitute a key nature-based solution (NbS) for Disaster Risk Reduction (DRR), which can be complemented by technical protection measures. However, ongoing climate change increasingly exposes forests to stressors and natural disturbances that reduce their resistance to future impacts and their capacity for recovery.

In this study, we transferred the concept of compound events to protective forests, defining them as multiple, spatially and/or temporally interacting climate-induced stressors and disturbances. Such events can alter forest structure, species composition, and spatial extent, thereby reducing the forests’ protective functions and effects against natural hazards and creating compound risks for people and infrastructure. For example, windthrow and bark beetle infestations can create large forest openings, increasing the likelihood of snow avalanche release.

Compound risks pose novel challenges for pre- and post-disturbance protective forest and natural hazard management. Given the high level of uncertainty and complexity involved, it is necessary to develop a shared understanding of compound risk. There is also a need to quantitatively assess compound risks to enable the implementation of effective protective forest management and compound risk mitigation strategies.

Based on a systematic literature review, we synthesized existing knowledge on compounding stressors and disturbances affecting protective forests to develop an operational definition of compound risk. To support its assessment and management, we proposed a risk-based decision-making framework grounded in adaptive pathways. We applied this framework to two case studies of compound events in forests protecting against rockfall and snow avalanche hazards. For each case study, vulnerabilities and opportunities were characterised through the development of a range of plausible scenarios. The framework further identified different types of actions to mitigate compound risk and evaluated their effectiveness across the defined scenarios. In an additional step, contingency actions were specified to enable risk-based interventions in response to changes in the system.

Overall, we demonstrate that this framework can support flexible and adaptive decision-making in protective forest and natural hazard management under uncertainty arising from compound risk.