If you plant it, they will come

Beaury EM, Patrick M, and Bradley BA. 2021. Invaders for sale: the ongoing spread of invasive species by the plant trade industry. Frontiers in Ecology and Environment, doi:10.1002/fee.2392. PDF.

More original research from the RISCC team suggests known invasive species continue to be spread via ornamental trade, including federal- and state-regulated species. For more information, or for access to state-specific data, please contact Eve Beaury (ebeaury@umass.edu).

Summary

Nearly half of invasive plants in the U.S. today were imported through ornamental trade, and imports of new exotic plants continue to rise. Measures have been taken to spread awareness about ornamental invasives, however it is unclear how effective these efforts have been at removing harmful invasive plants from ornamental trade. Therefore, Beaury et al. (2021) used Google and a database of nursery catalogs to identify which U.S. invasive plants are still marketed and distributed as ornamentals. Out of all 1285 invasive plants searched, 61% were available for purchase from an online, retail, or wholesale nursery in the lower 48 US states. This included about 50% of all species regulated by one or more state governments, several of which were found for sale in the state where they are currently being regulated. However, most sales of state-regulated species occurred in adjacent states, suggesting that regulations are effective for reducing within-state trade of invasives. Nonetheless, ornamental invasives continue to spread because of inconsistent state regulations. As climate change progresses, the U.S. will undergo rapid environmental changes that will cause plant ranges to shift into newly suitable habitats. The widespread availability of known invasive plants may allow unassuming customers to seed new invasions in areas becoming increasingly vulnerable due to climate change. Consequently, Beaury et al. (2021) suggests that states should work together to coordinate regulations regionally and promote public awareness of invasive plants in order to effectively protect our ecosystems against further invasion.

Take home points

  • 61% of 1285 U.S. invasive plants were found for sale as ornamentals within all the lower 48 states. This includes 343 of 688 state-regulated plant species and 20 of 98 federal noxious weeds.  Find the full list of invaders for sale here.

  • 1330 different online, retail, and wholesale nurseries sell invasives, and these vendors are located in all of the lower 48 United States. 

  • The number of times a species was found for sale decreased with the number of states within which a species was regulated. State regulations work, but more consistent regulations are needed to reduce sales.

Management implications

  • Ornamental trade continues to be a pathway for the introduction of known, high-impact invasive plants. This is particularly concerning as climate change makes new habitats vulnerable to invasion. 

  • States successfully reduced sales of their regulated invasive plants, but regulated species were often sold legally in neighboring states. Coordinating lists regionally may be a more effective strategy for reducing sales of invasives.

  • Spreading awareness of regulations (particularly across state borders) and marketing native alternative plants could persuade the public to stop buying invasive plants.

Keywords

Novel introduction pathways; management efficacy; range expansion; ornamental plant trade; plant regulations