Predicting Plant Invasions in an Era of Global Change

Intentionally and unintentionally, humans have moved thousands of plant species outside of their native ranges.  Some of these species have become invasive, spreading away from the sites of their initial establishment, and often negatively affecting native and managed ecosystems.  One prominent example in New England and many northern states is purple loosestrife (Lythrum salicaria), which invades and dominates wetlands, altering habitat and outcompeting native species.  Scientists and managers are concerned that global change, including

land cover change, altered nutrient cycles, increased global trade, and climate change, will promote plant invasions.  In this talk, I will review recent research which sheds light on the complex relationships between invasive plants and global change.  Components of global change that increase plant resources (e.g., rising CO2, N deposition) most consistently promote invasion.  However, changing temperature and precipitation can either help or hinder plant

invasion.  Moreover, both experimental studies and models suggest that invasive plants often respond in unpredictable ways to the combined effects of different components of global change.  Such variability adds uncertainty to existing risk assessments and other predictive tools.  Managers should be prepared for both expansion and contraction of invasive plants due to global change; leading, respectively, to increased risk or unprecedented opportunities for restoration.