Weed risk assessments and NREPA:
The Michigan Department of Agriculture and Rural Development regulates aquatic species through a Prohibited and Restricted species list, under the authority of Michigan’s Natural Resources and Environmental Protection Act (NREPA), Act 451 of 1994, Part 413 (MCL 324.41301-41305).
- Prohibited species are defined as species which “(i) are not native or are genetically engineered, (ii) are not naturalized in this state or, if naturalized, are not widely distributed, and further, fulfill at least one of two requirements: (A) The organism has the potential to harm human health or to severely harm natural, agricultural, or silvicultural resources and (B) Effective management or control techniques for the organism are not available.”
- Restricted species are defined as species which “(i) are not native, and (ii) are naturalized in this state, and one or more of the following apply: (A) The organism has the potential to harm human health or to harm natural, agricultural, or silvicultural resources. (B) Effective management or control techniques for the organism are available.”
- Per a recently signed amendment to NREPA (MCL 324.41302), MDARD will be conducting reviews of all species on the lists to ensure that the lists are as accurate as possible.
What is the purpose of a weed risk assessment?
MDARD uses the United States Department of Agriculture’s, Plant Protection and Quarantine (PPQ) Weed Risk Assessment (WRA) process (PPQ, 2015) to evaluate the risk potential of plants.
How is a WRA developed?
The PPQ WRA process includes three analytical components that together describe the risk profile of a plant species (risk potential, uncertainty, and geographic potential; PPQ, 2015).
- At the core of the process is the predictive risk model that evaluates the baseline invasive/weed potential of a plant species using information related to its ability to establish, spread, and cause harm in natural, anthropogenic, and production systems (Koop et al., 2012).
- Because the predictive model is geographically and climatically neutral, it can be used to evaluate the risk of any plant species for the entire United States or for any area within it.
- A stochastic simulation is used to evaluate how much the uncertainty associated with the risk analysis affects the outcomes from the predictive model. The simulation essentially evaluates what other risk scores might result if any answers in the predictive model might change.
- Finally, Geographic Information System (GIS) overlays are used to evaluate those areas of the United States that may be suitable for the establishment of the species.
For a detailed description of the PPQ WRA process, please refer to the PPQ Weed Risk Assessment Guidelines (PPQ, 2015), which is available upon request.
Considerations regarding the WRA process
- The WRA process is designed to estimate the baseline—or unmitigated—risk associated with a plant species.
- It uses evidence from anywhere in the world and in any type of system (production, anthropogenic, or natural) for the assessment, which makes the process a very broad evaluation. This is appropriate for the types of actions considered by MDARD (e.g., State regulation).
- Risk assessment and risk management are distinctly different phases of pest risk analysis (e.g., IPPC, 2015). Although MDARD may use evidence about existing or proposed control programs in the assessment, the ease or difficulty of control has no bearing on the risk potential for a species. That information could be considered during the risk management (decision making) process, which is not addressed here.
