Insect pests like forest tent caterpillar and spongy moth (Lymantria dispar) and diseases like hypoxylon canker may become more active and damaging in aspen-birch forests under a warmer climate.

Under a high emissions scenario, researchers forecast more insect pest damage in northern forests due to increased metabolic activity in active periods and increased winter survival. Drought-stressed trees are also typically more vulnerable to insect pests and diseases. The possibility exists for interactions among multiple stressors to lead to more severe climate change impacts. For example, warmer temperatures may simultaneously increase drought stress on trees and create conditions more suitable to some forest pests and diseases, which could combine to increase the risk of insect and disease outbreaks, tree mortality, and ultimately, wildfire risk.