Estimating Future Forest Fire Risk in Gävleborg County Sweden in 2041-2070 Following RCP 8.5

Abstract: Forest fires can act as an ecosystem service by providing habitat renewal, controlling pests, and reducing the risk of extreme fires, but can at the same time disturb an ecosystem negatively. Furthermore, forest fires release carbon dioxide into the atmosphere, damage property, and lead to health issues. With climate change, forest fires are expected to increase in both frequency and intensity in many areas of the world. However, models predict different results for future forest fire occurrence. The recent increase of forest fires in Sweden calls for a greater understanding of the future change in forest fire risk. The aim of this thesis is to estimate the future forest fire risk score and fire occurrence in Gävleborg county in Sweden in 2041-2070. The future forest fire risk was adjusted to climate projections of RCP 8.5. The method included a development of a simple model using the most important forest fire risk parameters in Gävleborg county in present-day. The construction of the model was done by a literature study as well as fitting the models risk score areas to observed fire data. A present-day estimation of forest fire risk score in 2006-2010 was done based on the developed model. A validation of the model against past observations of actual fire occurrence was performed and lastly the future forest fire risk score was predicted. The validation of the model showed okay agreement. The results showed an increase of forest fire risk score in Gävleborg county in the future compared to the present-day. The factors deemed most important for forest fire occurrence were temperature, precipitation, aspect, forest type and distance to water course and water surfaces. In conclusion, the increase of areas with ‘very high’ risk score and ‘high’ risk score in the predicted future scenario could indicate an increase of the total annual number of fires in the summer season from 12 in the present-day to 16 in a future scenario in Gävleborg county.