Development of wind and fire risk indices for climate-mitigation forestry

Afforestation has long been discussed as a nature-based climate mitigation solution. Although it could be an economic, green, and safe climate mitigation method, several studies suggest the possibility of unforeseen consequences depending on how it is implemented. An important aspect to be taken into account when designing af- and reforestation plans is the risk of damage to the new forest system in the face of climate warming. Recent studies have already shown an increase in both wind and fire damage risks in northern latitudinal forests related to climate warming, with strong winds leading to breakage of individual branches as well as in the knock-over of individual trees or even entire forest areas.

However, the forest system is complex, with a high number of feedback loops between different types of damage and between forest structure and ecological parameters. A few examples: Trees that are weakened by damage from pest outbreaks and snowfall are more susceptible to damage from wind and fire; Gaps in the forest that are created by management or damage both increase wind flow due to an eddy effect and create new forest edges with poorly adapted trees, increasing the risk of wind-throw.

Due to this complexity, the resilience to damage and therefore ability of forests to mitigate climate on a regional scale are still poorly understood. Understanding this complexity requires model work and extensive literature research, as most studies only focus on a few aspects of the forest system, such as the management type or wind effects. The aim of the study is therefore to develop adequate and future-proof wind- and fire risk indices that boreal forest managers can use to improve management strategies to make climate-mitigation forests more effective, resilient and damage resistant.

To do this, output from the Weather Research and Forecasting (WRF) model is used in combination with data on damage, forest management and forest structure to shed some light on possible feedbacks between forest systems and climate on a small-scale basis, in this case 3kmx3km. This information is then used to expand the Canadian Forest Fire Weather Index (FWI) to include ecological, management-related and forest structural parameters. As the structure of the existing FWI is climate-based, the wind risk index will be based on the developed fire risk index.

Our preliminary results show that wind damage was most common and extensive in the south-western coastal area of Norway over the last two decades. In contrast, fire damage was most prevalent in the south, with increased damage extent in the south-west of the country. Furthermore, the FWI shows that under an afforestation scenario in Norway, the mountainous region will have the highest frequency of days with medium to high danger of forest fires under climate warming. In this presentation we will discuss these preliminary results, as well as the methodology we will be using to develop the risk indices. Policymakers and forest owners alike will be able to use the risk indices to make the climate-mitigation forests more resilient against damage in a warming climate.