Contemporary fires are less frequent but more severe in dry conifer forests of the southwestern United States

This study brought together two spatially extensive, long-term datasets to quantify fire regime changes over the last three centuries in dry conifer forests in the southwestern US. At hundreds of tree-ring fire history sites, fire regimes were historically dominated by frequent and low-severity fires that effectively ended in the late 1800s. While the collapse of this fire regime and resulting change to forests is well documented, the extent to which recent increases in fire activity might fall within historical norms has not previously been rigorously analyzed.

The findings show that contemporary patterns of burning in dry conifer forests bear little resemblance to historical fire regimes in two important ways. First, despite rapid increases in fire activity observed over the last several decades, fires are still burning far less frequently now than they were historically. Second, trees in this forest type historically survived many fires over centuries, but recent fires are anomalously lethal.