Rethinking Invasiveness: Geographical Distribution and Abundance

Climate-smart invasive species management includes the proactive identification of potentially invasive species before they become widespread.  Past research conducted by a team of researchers with the Northeast Regional Invasive Species and Climate Change (RISCC) Management Network  has led to the development of decision support tools that identify range shifting invasive plants.  Although risk assessments often focus on the distribution (presence or absence) of invasive plants, a second paper authored by RISCC Management Network researchers indicates that abundance information might be a better indicator of invasiveness. In light of this work, Bethany Bradley, a co-founder of the RISCC Network, has worked with a group of collaborators to compile a comprehensive spatial database of invasive plant occurrence and abundance across the conterminous U.S., totalling nearly 5,000,000 observations recorded through 2022.  Their results have been published in Global Ecology and Biogeography. 

In their analysis, the team identifies 1,874 introduced plants reported in the conterminous U.S., of which 565 have a widespread distribution, occupy multiple habitats, and are locally abundant.  Their work  also notes species that have unexpectedly high abundance relative to their range sizes or length of time that they’ve been present in the U.S. - species that are prime candidates for further risk assessment as invasives.  This dataset has already been used to model climate-driven range shifts of abundant invasive plants in the eastern U.S. and associated models are presented as ‘future abundance habitat’ in selected county-level maps in EDDMapS. 

Take Home Points

• Introduced plants that have been observed at high abundance within your ecoregion are more likely to pose an invasion risk. 

Management Implications

• Many introduced species have become widespread and/or abundant within the conterminous U.S. A list of all species and their level of commonness can be found in Appendix S3
• Practitioners can create lists of abundant introduced species within their Level III EPA ecoregion and/or associated state using Appendix S4