A risk assessment based proactive management strategy for aquatic weeds in New Zealand

Abstract

Aquatic weeds are notoriously difficult to manage once established. This paper discusses a range of proactive management actions undertaken by regulatory authorities based on the assessment of risk posed by those organisms using the Aquatic Weed Risk Assessment Model (AWRAM). AWRAM scores potential risk characters such as habitat range, ability to displace other species, seed and vegetative propagule output, dispersal mechanisms, potential economic and environmental impacts, potential distribution and ease of control. Species with the largest sum of risk character scores are regarded as the worst potential aquatic weeds and AWRAM provides a decision support tool for management agencies. Management actions include prevention of deliberate introduction into New Zealand and subsequent spread within that country, as well as eradication programs targeting high-impact, low-incidence aquatic weeds species. Progress to date has been the exclusion from sale and distribution of 29 potential aquatic weeds and the ban from importation of a further 10 species. Current regulations have effectively ceased legal importation of aquatic plants into New Zealand, but evidence of illegal importation provides concern. Six freshwater weeds have been eradicated nationally and central and regional government agencies have initiated eradication programs for a further 13 aquatic weeds, with additional species managed in this way at a regional or island level. These proactive management activities are effective methods to achieve elimination or reduction of both propagule and colonization pressure of high-risk aquatic weeds, thereby reducing the likelihood of those species becoming widespread problems in the future.