Wildfire danger to increase due to climate change

SLF researchers expect an elevated wildfire danger in the Alpine Foreland from 2040 onwards due to changing meteorological conditions. The danger currently remains very low in that region, but there is likely to be a shift in this regard as a result of climate change.

There is likely to be a significant increase in the danger of wildfires through the 21st century. Indeed, the expectation is that by 2100 the danger will be high even in regions where it is very low today. Those are the findings of a study by Julia Miller, a PhD student in the Hydrology & Climate Impacts in Mountain Regions research group at the WSL Institute for Snow and Avalanche Research SLF.

Forecasts show that the potential danger will continue to increase, but from 2040 onwards it will exceed the natural range of climate fluctuations and so will be attributed to climate change from then on. Taking the example of the Bavarian Alpine Foreland, this means that the meteorological wildfire danger will rise more rapidly from 2040 onwards, developing from low at present to high by the end of the 21st century (Fig. 1). A weather-related event that currently occurs only once every 60 years will happen on average every 10 years by 2090 (Fig. 2). The projections also show that favourable weather conditions for wildfires will occur earlier in the year than today, i.e. in or around May. Currently, the wildfire season often begins in June. Vegetation that is already dry also means that fires can start more easily and get out of control more quickly. "Therefore, even regions with a temperate climate will need to prepare for wildfires in the future," says Julia Miller. Such preparations range from water reservoirs for fire-fighting helicopters to warning signs alerting local people to the danger.

"The number of days when the wildfire danger is at least 'high' will more than double by the end of the 21st century," predicts Miller. This trend is reinforced by factors such as hot, dry and windy weather. Summer heatwaves and drought events also reduce soil moisture, increasing the flammability of the vegetation. Miller is here addressing an issue that the Intergovernmental Panel on Climate Change (IPCC) raised in a 2021 report. For her study, she used a number of climate variables and took natural and climate-related fluctuations into account. She made her forecasts based on the Canadian Forest Fire Weather Index (FWI). The FWI is based on meteorological data and is a numerical rating of fire intensity and thus how readily combustible material (e.g. trees, dead wood, dry leaves) can ignite and how rapidly a fire can develop. While the Mediterranean region and Western Canada have historically been prone to fire and have been extensively studied at a broader regional level, scientists have so far paid less attention to wildfires in the temperate regions of Europe. For her research, Miller used weather data from 'hydrological Bavaria' (the river catchments of the Danube, Main and Elbe), which she divided into four geographical and climatic subregions.

Given that the FWI does not take the vegetation situation into account, in her next study Miller would like to identify the role played by soil moisture and vegetation dryness in wildfire danger. She also analyses the climatic conditions under which the danger is greatest and highlights the regional differences within Europe. "Our aim is to show that wildfires in Europe can have different drivers. To this end, we would like to identify regional and seasonal differences in order to better understand the climatic factors that lead to large and uncontrollable wildfires," explains Miller.




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