A review of the impacts from invasion by the introduced kelp Undaria pinnatifida

Report: TR 2016/40

Author: K James (Insitute of Marine Science, University of Auckland)

About this report

Invasive species are considered one of the foremost threats to marine ecosystems. Undaria pinnatifida is considered one of the most dangerous invasive seaweed species in the world; however, information around impacts from invasion remains limited and is often contradictory.

This report provides a review of the impacts from Undaria invasion to improve the ability of those managing impacts from marine invasive species to appropriately define (and weight) risks associated with Undaria invasion.

It concludes that Undaria invasion can modify intertidal and subtidal communities and that impacts can occur across all trophic levels. While there are knowledge gaps, enough evidence is available to warrant real concern over Undaria invasion and the subsequent ecological impacts on native communities.

The presence and impacts from Undaria invasion undermine efforts to conserve biodiversity and representative native ecosystems in particular. Furthermore, future interactions between environmental stressors such as high levels of coastal modification, eutrophication, and ocean warming may give Undaria a significant advantage over native species as community resilience is lowered.

It is suggested that risk assessments are used to provide timely information to decision-makers on risks posed by Undaria invasion. The set of attributes which make Undaria one of the most invasive species in the world, and a current lack of tools or methods to control or eradicate Undaria post invasion, make interception or removal of pathways to introduction the only effective approach for limiting impacts. Better understanding around the invasion patterns and processes associated with the spread of Undaria, human mediated pathways in particular, will allow the development of strategies to reduce the spread of Undariaand hence mitigate ecological impacts.

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A review of the impacts from invasion by the introduced kelp Undaria pinnatifida
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