Threats to North American forests from southern pine beetle with warming winters

In coming decades, warmer winters are likely to ease range constraints on many cold-limited forest insects^1-5. Recent unprecedented expansion of the southern pine beetle (SPB, Dendroctonus frontalis) into New Jersey, New York, and Connecticut in concert with warming annual temperature minima highlights the risk that this insect pest poses to the pine forests of the northern United States and Canada under continued climate change⁶. Here we present projections of northward expansion in SPB-suitable climates using a statistical bioclimatic range modeling approach and current-generation general circulation model (GCM) output under the Representative Concentration Pathway (RCP) 4.5 and 8.5 emissions scenarios. Our results show that by the middle of the 21^st century, the climate is likely to be suitable for SPB expansion into vast areas of previously unaffected forests throughout the northeastern United States and into southeastern Canada. This scenario would pose a significant economic and ecological risk to the affected regions, including disruption of local ecosystem services⁷, shifts in forest structure⁸, and threats to native biodiversity⁹.