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8.03.00 - Natural hazards and risk management


Frédéric Berger, France


Peter Bebi, Switzerland

About Unit

Natural hazards in forest environments are increasing significantly due to anthropogenic pressure and a higher frequency of extreme weather conditions. It is thus urgent to find solutions for managing natural and urban forests so that their resilience to disturbances is increased against a background of climate change. Society also needs to shift from the maximum sustainable yield paradigm to an adapted forest management which builds ecological resilience through a holistic understanding of the ecological and physical processes involved. We unite researchers and practitioners to explore new concepts, models and tools for improving natural and urban forest resilience. We examine resistance and resilience at different scales: tree individual, forest stand and landscape, and ask how resistance and resilience can be integrated across these scales. We focus on common hazards that disturb forest systems (i) geomorphologic, e.g. landslides, water and coastal erosion and snow avalanches (ii) weather, e.g. strong winds, snow, ice and rain storms and extreme temperatures and (iii) a topic new to our research unit; radioactive contamination.

State of Knowledge

Forests subject to severe anthropogenic pressure, or naturally occurring in marginal environments, are extremely susceptible to climate change. Extreme weather events, such as excessive temperatures, storms and droughts will have short- and long-term effects on tree health and mortality. Tree uprooting or breakage of stems or branches in response to soil-saturating rains and flooding, strong winds, or heavy ice or snow loading during a storm or damage induced by avalanches, or landslides after heavy precipitation in mountainous terrain, will require a rapid response from forest managers. Any immediate danger to people and infrastructure can be dealt with and insurance claims pursued. However, the long-term consequences can be more difficult to discern. For example, storm damage which has injured trees without causing immediate mortality can weaken trees, rendering them susceptible to insect and pathogen attack, and ultimately resulting in death. Physical damage within branches, stems, and roots may not be evident upon initial inspection and could result in future structural failures of trees which withstood the initial event, but were not removed. In this group, we focus on both the short- and long-term consequences of natural hazards on natural, plantation and urban forests. We explore how forests can withstand geomorphological, weather and radioactive hazards and, through either natural processes, or adapted management methods. We also investigate the mechanisms of ecosystem failure and resilience if a disturbance does occur in a forest. The novelty of our group is that we ensure that different spatial and temporal scales are represented, allowing a holistic overview of the problems encountered and solutions envisaged.