Increasingly, Ted Grosholz's research is addressing the interaction between climate change and biological invasions. As the result of participation in an NCEAS (National Center for Ecological Analysis and Synthesis) working group on climate change and invasive species, he has continued his collaborative work on synthetic analyses of climate change impacts on the invasion process that began with participation in an NCEAS working group on climate change and invasive species. One project included a comprehensive study of field and lab experiments that varied climate change variables and assessed the impacts simultaneously on native and non-native species. The results of these analyses demonstrated that in terrestrial systems, native and non-native species responded similarly to experimentally manipulated climate change variables. However, in aquatic systems (freshwater and marine), increased temperature and CO2 more strongly impacted native species relative to introduced species. Overall, Grosholz has found that with respect to future climate change projections, aquatic systems may be particularly at risk from invasions. This may help managers determine which systems should be the priority for reducing stressors that can be managed in order to lessen risks due to changing climates. In a second project, he brought together the few dozen studies that have documented the effects of extreme climatic events on biological invasions. As trends in temperature, pH, sea level rise and other markers of change increase, so does the magnitude and frequency of extreme events. Most of the evidence suggests that these events selectively facilitate successful growth and spread of existing invaders.
This work is significant in bringing attention to two key issues. The first is the focus on extreme climate events, which are likely to have the greatest influence on ecosystem function in the future. The second issue is the effects on these rare events on invasions, since most other studies to date have only addressed the effects of mean values of climate variables on invader success. The Grosholz Lab has developed a set of analytical tools for distributional and demographic data from invasive species to assess invasion potential at different invasion stages. They have used data from three case studies (a vine, a marine mussel, and a freshwater crayfish) using current and projected climatic conditions to generate three examples of this integrated assessment approach. Their results show that the particular climatic variables can have contrasting effects or operate at different intensities across habitat types that can be invasion stage specific. They found that projected climate trends may increase the likelihood of invasion in some habitats and decrease it in others. This approach is likely to provide information that can inform management decisions and help to optimize invasion phase-specific management efforts for a wide range of invasions.