Northward shifts in tree species distributions are a potential impact of climate change on northern hemisphere forest ecosystems.  It has been hypothesized that some tree species may become extirpated as climate change effects may exceed their ability to propagate northward.  The goal of this study was to compare tree species compositions in northern urban areas and middle latitude/southern forests in the eastern U.S. as an indicator of the potential for urban trees to serve as a seed source for future migration.  The tree compositions of urban forests in selected cities of the northeastern U.S. were compared to those found in forestland inventories of middle and southern latitudes.

Results/Conclusions

Results indicated that a number of tree species, endemic to eastern U.S. forests of the middle and southern of latitudes, are currently present in urban forests north of their current range.  Furthermore, results indicate that urban forests of northeastern U.S. may serve as a seed source to increase rates of possible tree migration.  The same mechanism that facilitates invasive species dispersal through northern U.S. urban centers (e.g., emerald ash borer and Chicago’s port-of-call) could perhaps facilitate native tree migration under a scenario of a warming climate.