Small trees are often removed from conifer forests in dry areas to reduce the risk of wildfires, but a US study has revealed that insect outbreaks pose a greater threat to such forests than fire does.

William Baker and Mark Williams at the University of Wyoming in Laramie studied records of fires and insect outbreaks in dry forests in the western United States from 1999 to 2012, and found that insects caused the loss of 5.6 times more forest area than did wildfires. The team also analysed land surveys from the late nineteenth century and found that small trees — of about 40 centimetres or less in diameter — made up almost 62% of total trees, a higher proportion than was thought.

The findings suggest that, historically, forests were resilient because of the smaller trees, and that removing these to control fire risk could be misguided.

Front. Ecol. Evol. http://doi.org/zfj (2015)