A Risk-Assessment System for Screening Out Invasive Pest Plants from Hawaii and Other Pacific Islands

Abstract:  Ecosystems of Hawaii and other Pacific Islands have been greatly affected by invasive pest plants, and ongoing, deliberate plant introductions make it likely that additional pest plants will become established. We tested the ability of a modified version of the Australian and New Zealand weed risk-assessment system to identify pest plants in Hawaii and other Pacific Islands. We used information taken from outside Hawaii to predict the behavior—"pest" or "not a pest"—of almost 200 plant species introduced to Hawaii and other Pacific Islands. The screening system initially recommended further evaluation of 24% of these species, but an additional secondary screening was applied to this group, thereby reducing the rate of indecision to only 8%. To independently test the accuracy of the screening system, we compared its decisions—pest or not a pest—to opinions of 25 expert botanists and weed scientists who had substantial field experience in Hawaii or other Pacific Islands. We asked the experts to rate each species as "major pest,""minor pest," or "not a pest" in native or managed ecosystems. The screening system correctly identified 95% of major pests and 85% of nonpests. Among minor pests identified by the experts, 33% were classified as nonpests by the screening system. Use of the screening system to assess proposed plant introductions to Hawaii or other Pacific Islands and to identify high-risk species used in horticulture and forestry would greatly reduce future pest-plant problems and allow entry of most nonpests. The screening process is objective, rapid, and cost-efficient. With minor modifications, it is likely to be useful in many parts of the world.