Invasive plants, forest pests, diseases, droughts, and floods are expected to become more damaging under climate change, and these factors may interact in unpredictable ways. Drought and increased temperatures due to climate change have caused extensive tree death across the Southwest. In addition, winter warming due to climate change has exacerbated bark beetle outbreaks by allowing more beetles, which normally die in cold weather, to survive and reproduce. Wildfire and bark beetles killed trees across 20% of Arizona and New Mexico forests from 1984 to 2008. The Mexican pine beetle, previously known only in Mexico, has been recorded in the southwestern United States and represents one of several species of Mexican bark beetles that may expand into Southwest forests with continued warming trends. Severe wildfires are also expected to become more frequent under climate change, particularly in high-elevation forests.