Risk assessment tool for invasive plant spread in the northern Rocky Mountains

Photo Credit

U.S. Fish and Wildlife Service

A field of the invasive grass, Ventenata dubia.

A number of tools are available to land managers for assessing the risk of invasive plant species, such as USGS INHABIT and the widely used Australian Weed Risk Assessment. However, current risk assessment tools are not useful at a local project level, and they are not specific to Forest Service activities such as thinning, prescribed fire, grazing, and recreation. This project supports the Forest Service National Environmental Policy Act (NEPA) process by creating a standardized platform for quantifying the risks of introduction, invasion, and spread of invasive plants when planning resource management activities. It uses a ranking approach and parameters such as dispersal vectors (how a plant can spread) and occupied habitat (how widespread a plant is already) to quantify the likelihood of introducing certain invasive plant species. 

Under this framework, potential risks can be clearly compared across several scenarios proposed for a project area (comparing various action and no action alternatives). We also plan on incorporating specific fire management activities in the platform, including historical wildfire, prescribed burns, and thinning operations.

Keywords: Invasive Plant Species, Risk Assessment, Environmental Assessment, Fire Management, Grazing, Recreation Impacts

Key Research

Photo Credit

Rebekah Fields, University of Montana Spatial Analysis Lab

This conceptual version of the planning tool shows the process for determining the risk of a given management activity (x) introducing or spreading a plant species (y) in the Northern Region of the Forest Service. 
Starting in Box A, follow the arrows through the five major determining factors, which each can add up to one point, for a total of five possible points. Box A and C are yes/no responses. A “Yes” response adds 1 point and the decision tree continues, while a “No” response adds 0 points and the decision tree ends there. Boxes B, D, and E are all variable factors that range between 0 and 1. Box B uses the USGS INHABIT tool habitat suitability ranking, and Boxes D and E use the provided equations. Once all the boxes are calculated, the final score is tallied, which corresponds to a risk threshold at the bottom left of the figure.

Land management activities can unintentionally spread invasive plants, with long-term consequences for habitats, water systems, and potentially wildfire risk. This project offers insight into the risks and trade-offs of management actions through a risk-assessment decision tree framework designed to generate outputs that depict the likelihood of introducing invasive plant species when undertaking specific activities across a defined project area. These outputs will provide information to facilitate day-to-day planning for more resilient landscapes.

The framework will include an interactive application where resource managers can choose an activity from a dropdown menu, select or upload a shapefile for the location, and receive a set of results. These include the risk of introducing invasive plants and the reasoning behind each risk rating, which facilitates decision documentation.