The devastating impacts and staggering mitigation and control costs of invasive species are well documented. Recent estimates place the annual economic impacts of aquatic invasive species in the United States at $166 billion and globally at $345 billion, with invasive aquatic invertebrates accounting for 70% of the global total. In addition to these economic impacts, invasive species also cause pervasive changes in ecosystem structure and function. Preventing invasions is widely recognized as the most cost-effective management action, and a federal early detection and rapid response (EDRR) strategy has been developed through a series of executive orders that includes horizon scanning as part of the initial EDRR planning phases.

A collaborative core team of Dr. Mike Kaller, of RNR; Dr. Rodrigo Diaz, of the Department of Entomology; Dr. Wes Daniel, of the U.S. Geological Survey; RNR graduate students Joe Brown (B.S., 2022; M.S., 2024) and A. Henry Gasperecz (B.S., 2022); RNR research associate Kaydence Dubroc; and USGS scientists Cayla Morningstar and Audrey Jordon are working on a U.S. Fish and Wildlife Service-funded global horizon scan of potentially invasive aquatic and terrestrial invertebrates. The horizon scan involves several stages: 1) building a list of potential invasive species based on published literature; 2) climate-matching to determine suitability of environmental conditions in the United States for each species; 3) a review and risk assessment scoring process by taxonomic experts; and 4) consensus building among taxonomic experts to produce a final watch list of potential invasive species with the highest risk of invasion and impact. Brown served as principal core team meeting coordinator and conducted climate matching as part of his thesis research and worked with Gasperecz, Jordan and recent graduate Emillee Monahan (B.S., 2025) in the list building process. Consensus building began with a kickoff meeting at the Ione Skye Burden Conference Center in November 2023. The 28 attendees also included RNR faculty member Dr. Garrett Hopper; current and former RNR students Dr. Patricia Wooden (M.S. 2019), Jake Duhe and Bailey Pentz (B.S. 2022) and Emily Steen; and Drs. Chris Carlton and Britanny Owen, from entomology.

List building resulted in 7,617 potential invasive invertebrate species, including 5,781 insects, 889 arachnids and 383 mollusk species. The magnitude of the climate matching scores reduced the list to 587 taxa (550 species and 37 genera) for consensus building, which resulted in a watch list of “high” and “moderate” risk organisms. Once reviewed, this list will be distributed to the U.S. Fish and Wildlife Service, U.S. Department of Agriculture and other agencies concerned with the spread of invasive species.

The golden mussel (Limnoperna fortunei; photo by P.R.F. Fernandes De Oliveira, C. Carvalho Rodrigues, M. I. Grano-Maldonado, and T. Lopes Rocha) is shown at the top. At the bottom left is the demon shrimp (Dikerogammarus haemobaphes; photo by A. J. Cann), and at the bottom right is the brush-clawed shore crab (Hemigrapsus takanoi; photo by Hans Hillewaert). All three species were identified as high-priority targets for prevention efforts.