Over the next few decades, global warming-related rises in winter temperatures could significantly extend the range of the southern pine beetle—one of the world’s most aggressive tree-killing insects—through much of the northern United States and southern Canada, says a new study. The beetle’s range is sharply limited by annual extreme temperature lows, but these lows are rising much faster than average temperatures—a trend that will probably drive the beetles’ spread, say the authors. The study was published today in the journal Nature Climate Change.