Extensive land development, invasive species and too many deer may make it difficult for tree migration to keep pace with climate change in the Northeast, according to newly published research. The study, led by Kathryn Miller, a plant ecologist with the National Park Service Inventory and Monitoring Division, and Brian McGill, a University of Maine professor of ecological modeling, analyzed U.S. Forest Service data covering 18 states from Tennessee to Maine. The researchers found a large swath of land in the mid-Atlantic states that was severely lacking in forest regeneration. Even where present, species regenerating on the forest floor were different than those making up the forest canopy. Earlier studies have raised concern about regional regeneration, but this is the first to document the sheer extent and severity of the problem.