Can Forest Plants Make a Comeback? Overcoming Decades of Over-browsing by Large Herbivores

Over the past several decades, changes in land use, extirpation of predators, conservation measures, and climate change have driven rapid and uncontrolled increases in large herbivore populations around the world. In temperate forest systems, selective foraging by overabundant ungulates has been negatively impacting the diversity and structure of plant communities for many years, with cascading impacts on arthropod and songbird communities as well. Species loss is often so complete that plant communities cannot recover diversity even when ungulate densities are reduced. However, an emerging body of research documents common landscape features providing localized relief from intense herbivory pressure. In these locations, diverse plant communities flourish, and they may also be effective propagule sources for re-colonizing the landscape if ungulate densities return to historical levels. Here, I explore the history and impacts of white-tailed deer herbivory on eastern North American forests (Chapter 1), I report the results of a deer exclosure experiment showing the legacy effects of chronic over-browsing (Chapter 2), and I present a systematic review of refuges from ungulate herbivory worldwide (Chapter 3). Despite the intense pressure of long-term herbivory and the persistence of legacy effects, refuges provide hope for a healthier and more diverse forest plant community in the future.