Assessing Urban Forest Threats across the Conterminous United States

Abstract

Numerous threats to urban forests are assessed for the conterminous United States, including projected changes in urban tree cover, air temperatures, precipitation, aridity, sea level rise, wildfires, and flooding, as well as threats from hurricanes, tornadoes, ice storms, and insects and diseases. All potential threats were integrated into a cumulative threat index to illustrate which areas of the United States will likely face the greatest overall threat to their urban forests. Urban forests with the greatest cumulative threat per unit area are in the eastern United States, particularly in some coastal counties. Urban forests that have the greatest cumulative threat proportional to the percent of the county that is urbanized are in the highly urbanized areas along the DC–Boston corridor and in other metro areas (e.g., Atlanta, Georgia; Indianapolis, Indiana; Columbus, Ohio; Houston, Texas; Charlotte, North Carolina). By understanding local urban forest threats, management plans and policies can be enacted to help mitigate the impacts of and adapt to future threats to sustain healthy urban forests and associated benefits. Study Implications: By understanding the magnitude and variation in potential urban forest threats, forest managers can be better prepared to potentially minimize and adapt to future urban forest damage. Threat type and intensities of threats vary by location. Understanding the distribution and intensity of urban forest threats can be used to help direct policies and forest management plans to sustain long-term urban forest health. A tool to assess urban forest threats by county is available in the supplemental materials.