Why are plants being screened using a weed risk assessment?

The purpose of the weed risk assessment  is to identify high-risk species (likely invasive pests plants), allowing us to make informed decisions that will reduce the economic and ecological harm caused by invasive plants in Hawaii and on other Pacific Islands.  Of course, many introduced plants provide significant benefits to humans, and such benefits also need to be considered when making planting or importation decisions. 

If you are unfamiliar with invasive pest problems in Hawaii, you may wish to see the overview: The silent invasion

Are the weed risk assessments legally binding?

No. The assessments allow you to make informed decisions.

How are weed risk assessments done?

The weed risk assessment (WRA) uses  49 questions to obtain a score for each species.  A high scoring plant poses a high risk of becoming an invasive pest in Hawaii and other Pacific Islands.  The weed risk assessment is a pro-active tool to identify plants that pose the highest risk of causing ecological or economic harm. It is based on the species' biology, geographic origin, and pest status elsewhere as well as published information on the species' behavior in Hawaii. It does not make use of unpublished observations on the species' behavior in Hawaii.

Blank assessment sheet

How well does the assessment system work?

Based on test runs with nearly 200 plant species, the weed risk assessment system correctly identifies approximately 95% of serious pest plants in Hawaii and other Pacific Islands. The system correctly classifies 80-85% of non-pest plants.

      More details on scientific findings

Can WRA ratings change?

The goal of the assessment process is to provide the best available information about the behavior of introduced plants in Hawaii and on other Pacific Islands. Currently, there are two processes by which the WRA rating for a species may change: 1)New or overlooked published information could change the answers to one or more of the 49 risk assessment questions, thereby changing the WRA score and rating, or 2)Unpublished information reported to and reviewed by a committee of plant experts (HEPEP) indicates that an "ok" rated species currently causes significant harm in native or managed ecosystems of Hawaii. This second process is evolving. Nevertheless, in the interest of providing the most accurate assessments possible, we invite you to submit information:

    Report new or missing information

Why can't I find an assessment for my favorite species?

Please use our search interface to be certain that your species is not listed under a synonym. We are working to complete additional assessments. If you would like to recommend a species for assessment, please contact Teresa Trueman-Madriaga (Kaulunani Urban Forestry Program, ttm@hawaii.rr.com)

back to main page