Maintain or improve the ability of forests to resist pests and pathogens

Many forest pests and pathogens are expected to expand or shift their ranges under climate change, and climate change may also increase the susceptibility of urban forests to damage from pests and pathogens through increased stress. Avoiding the introduction of pests is often not possible, but certain tactics may increase resistance of trees and forests to these stressors. The tactics are similar to those outlined for nonurban forests. The primary difference is likely to be a much greater ability and incentive to manage individual trees in urban forests.

Climate change may result in increases in biological stressors such as pests, pathogens, and invasive plant species. Urban areas are especially prone to attacks by nonnative pests and pathogens. Pests that are currently limited by cold temperatures or growing season (e.g., hemlock woolly adelgid in New England) could also affect urban areas sooner than surrounding rural areas due to the effects of the urban heat island. Reducing or eliminating stressors that might make a tree more susceptible to new or existing pests or pathogens will be important to maintaining forests in urban areas.