Regional differences in infilling and land-use conversion characterize woody cover increases across the Eastern United States

Trees and shrubs are expanding into historically open ecosystems across the globe, threatening ecological function and ecosystem services. Across much of the eastern U.S., increasing woody cover has been associated with ecological degradation of forest and savanna ecosystems, and more recently, heightened large wildfire risk. Understanding patterns in woody cover increases will be paramount for assessing potential ecological outcomes and developing region-specific management approaches. Using remotely sensed land-use and vegetation cover data, we quantified changes in woody cover between 2001 and 2021 across land-use types in the eastern U.S. to determine the relative contribution of forest infilling and land-use conversion to woody cover increases. Woody cover increased across a range of land-use types in the eastern U.S. including wetlands, pasturelands, and forests. Infilling of deciduous forests and encroachment in open land-use types such as pasturelands dominated the northeast. In contrast, high levels of land-use conversion from non-woody land-use types to forests along with increasing woody cover in wetlands dominated the southeast. Our findings suggest that increasing woody cover in the eastern U.S. likely reflects both intentional increases of woody cover by silviculture as well as unintentional increases tied to wetland woody encroachment and forest densification. Our findings highlight areas to target ecological impact assessments and management efforts. Further, we demonstrate a growing need to assess the potential impacts of expanding pine plantation area on forest ecology and changing wildfire risk.

Forest Ecology and Management