Ecological risk assessment for invasive or non-indigenous species is a developing field of study. Most research on the risk assessment of invasive or non-indigenous species have focused on hazard and exposure,  not on risk as currently understood or at a regional scale. At a regional scale there are always multiple other stressors, a variety of environmental gradients, spatial heterogeneity and a wide variety of valued characteristics.  These factors make estimating risk a daunting but achievable task. 

In the last several years the Institute has conducted several research programs to develop a risk assessment framework for invasives.

Conceptual Model Development and Testing for Invasive Species

This US Environmental Protection Agency funded project was to develop a conceptual model and eventually an entire computational framework for estimating risks due to invasives. The conceptual model was derived from Landis (2004) and the relative risk model approach. Into this basic model was incorporated the Hierarchical Patch Dynamics Paradigm as proposed by Wu and David (2002).

The risk assessment framework was then tested using the European Green Crab and Sargassum as test invasives at Cherry Point, WA. After this initial testing the risk assessment framework was applied to the Asian Oyster within the Chesapeake Bay and the Nunn Moth in the Mid-Atlantic States. The results of the risk assessment on the European Green Crab have been published (Colnar and Landis 2007 download) and the full EPA project report " Development of a conceptual model for non-indigenous species for the Mid-Atlantic States” is available.

As part of this project we also constructed a simulation model to investigate the relationship between landscape patch structure, toxicants, and competitive interactions in the establishment of an invasive species. This modeling effort gave rise to the beach head hypothesis, where the probability of introduction of an invasive is improved by having a patch free of competition from its native competitor until a sufficient population size has been established. The invasive then uses this beach head as a location for further colonization. The study was recently published (Deines, Chen and Landis 2006 download )

Risks due to Cross Border Transportation of Invasive Species

Impacts of non-indigenous invasive species (NIS) are a multi-million dollar cost to society every year.  Incongruities exist between the Canadian and American policies that regulate the introduction and control of invasive species.  Policies may ineffectively overlap across terrestrial, freshwater, and marine jurisdictions.  NIS are easily overlooked at border crossings due to the small size of propagules and because immigration, customs, and security concerns take precedence.  The Relative Risk Model was used to conduct an ecological risk assessment to evaluate the risks posed by human mediated transport of NIS across the Washington State-British Columbia border.  This project investigated the terrestrial, freshwater and marine transport pathways of invasive plants and animal species to the major habitat types in Washington, using Western Canada as the hypothesized source.  Risks of impacts by NIS were calculated for economic, cultural, and ecological endpoints of importance to stakeholders. 

The RRM results indicated that the transport pathway with the highest risk was freshwater recreational boats, which had a higher relative risk score than the next three highest scores, freight, trucks, and ships, combined.  Pathways with the lowest risk were containers, garden escapes, and trains.  The heavy weight of the freshwater pathway was driven by the fact that all three high risk NIS stressors were freshwater species; zebra mussel, purple loosestrife (semi-aquatic) and Eurasian watermilfoil.  The fact that all three freshwater NIS were ranked as high risk NIS due to their aggressiveness in out-competing native species heavily influenced the other risk scores (risk to endpoints, habitats, and subregions).  For instance, subregions with higher amounts of freshwater habitats tended to have high risk scores also.  The subregion of highest risk, the King-Snohomish-Pierce Tri-County region, has many freshwater boating locations; however, the risk score was also heavily influenced by the mere fact that as the urban hub of Washington, this subregion accommodates high volumes of all the various transportation modes, providing direct linkages (pathways) to other regions.

This program was supported by the Border Policy Research Institute of WWU and funded by the US Department of Transportation.

A PDF of the Final Project Report is Available for download.

For more information contact Wayne G. Landis email: wayne.landis@wwu.edu Contact Information: Institute of Environmental Toxicology, Huxley College of the Environment, MS 9180, Western Washington University, Bellingham, WA 98225-9180. Phone: 360-650-6136