Insect pests and diseases such as beech bark disease and hemlock woolly adelgid could become more problematic in spruce-fir forests under a warmer climate.

Climate change may amplify several major stressors that are already affecting this forest system. Several pests, including beech bark disease and hemlock woolly adelgid, currently affect many forests. Studies suggest that insect pests may increase in northern forests due to increased metabolic activity in active periods and increased winter survival. Insect pests, such as the hemlock woolly adelgid, are expected to cause more frequent and severe damage under climate change. Pests such as Asian longhorned beetle may present new risks as they expand, and new pests present unknown risks. Trees stressed by heat, drought, or disturbance are also typically more vulnerable to insect pests and diseases.