Does tree removal along railroads in Sweden influence the risk of train accidents with moose and roe deer?
After the storm Gudrun in 2005, the Swedish Transport Administration started clear-cutting of railroad corridors to reduce the risk of trees falling down on the tracks. Simultaneously, train accidents with moose and roe deer have become more frequent and the costs for consequent delays and repairs of engines are of growing concern. There is reason to assume that tree-clearance of railroad corridors may have contributed to an increase in number of accidents with moose and roe deer because the cleared areas provide attractive forage and thus may attract wildlife. The objective of my study was to investigate how clearing of trees affected the number of accidents with moose and roe deer. I compared deer-train collision frequencies before and after clearance of the selected railroads and compared these with uncleared control railroads in a BACI (before-after control-impact) approach. I have further investigated possible differences between regions and seasons. The results suggest that although there was a significant increase in the frequency of accidents on both controls and tree-cleared railroads over time, there was no effect of tree-clearance. Only in two regions and only during the summer months, significantly more accidents were observed along cleared sections. However, when performing a Bonferroni correction, the p-values were very close to the adjusted significance level. I discuss possible reasons for the observed increase and the lack of effect of tree clearance. More research is needed to unveil the reasons for the overall increase and to better understand why and how train-deer collisions occur.