Modelling Multiple Interconnected Hazards to Forests in a Changing Climate

Forests face increased threats from multiple hazards, with clear evidence of rising levels of disturbance across the world. In Europe part of this increased disturbance is from the increasing areas of forest across the continent, part is due to the management of the forests, and part is due to the changing climate. Recently the levels of damage have become alarming, with windstorms causing catastrophic damage, forest fires appearing in new and unexpected locations, and extended droughts followed by bark beetle infestations leading to very high mortality in Norway spruce across Central Europe.

The disturbance agents that affect forests are often linked together so that, for example, drought can lead to bark beetle outbreaks, windstorms will often lead to secondary damage from bark beetles, and dead wood from any disturbance can raise the fuel loading in the forest and increase the risk and intensity of any subsequent forest fires. Usually when forest risk has been studied or modelled each disturbance has been studied and modelled separately. In this paper we present a modelling effort to link together, in the R software environment, existing and new disturbance models for wind (fgr), bark beetles (IpsR), drought (SPEI) and forest fires (cffdrs). When coupled with climate sensitive growth models we are able to investigate predicted levels of damage until the end of the century for different climate scenarios. The disturbance models have been linked to the European Forest Dynamics Model (efdm) to assess levels of risk across Europe, and they have been linked to the 3-PG growth model (r3PG) to assess forest risk across Germany at a finer spatial scale. The results allow us to determine the effect of different forest management options and to search for optimal management approaches that can help in the development of more climate resilient forests.