There is a general need in invasive species research to quantify the potential habitat of invasive plant species. We were interested in modeling the shifts in suitable habitat over time and environmental space, especially in the face of climate change. Many readily available climate scenarios are only available at very coarse spatial and temporal resolutions (e.g., 0.5° model outputs for the year 2100), which are not fine enough to be useful to local resource managers. We used 1-km climate scenarios projected to the years 2020 and 2035 for the continental United States, to get a finer look at potential invasive species habitat distributions. We chose 10 species with a broad range of characteristics to model, some more recently introduced, some well established, some habitat-generalists, and some habitat-specialist species. We harvested most of the data from on-line sources, especially the National Institute of Invasive Species Science (www.NIISS.org). We then used maximum entropy modeling (Maxent) to create three models for each species: (1) current potential habitat suitability, (2) potential habitat suitability in 2020, and (3) potential habitat suitability in 2035.
Results/Conclusions
Our potential habitat maps for each species showed areas where habitat suitability remains stable with climate change, areas where habitat suitability is increasing, and areas where habitat suitability is decreasing. Area under the curve (AUC) values for the models ranged from 0.92 for Pennisetum ciliare to 0.84 for Celastrus orbiculatus, suggesting strong and predictable species-environment matching. We examined the trends in potential habitat shifts by species and identified the implications of the leading and trailing edges of invasion for land managers. At the leading edge of the invasion, plant spread is constrained by diffusion, but this may not be a hard boundary if the species has adequate time to spread. At the trailing edge of the invasion, species may not be extirpated immediately, because it may be well entrenched with an adequate seed bank for persistence. If the habitat is no longer suitable, eventually the seed bank may be exhausted and the plant species may be extirpated in that portion of the range. These ideas and concepts have important implications for invasive species management under varying rates of climate change.
