Sea Urchin Removal as a Tool, Not a Solution: Practical Lessons for Kelp Restoration in Aotearoa New Zealand

Abstract

The increasing awareness of the extent of urchin barrens and impacts of sea urchin overgrazing on rocky reefs in Aotearoa New Zealand has led to a rapid increase in the use of sea urchin removal as a tool for kelp forest restoration. Here, we review these restoration projects, focusing on three case studies, with the aim to provide context on what urchin removal does and does not achieve and guidance on when, where and how it might be both ecologically and culturally appropriate. At least fifteen known iwi Māori, hapū, community and research‐led urchin removal projects are underway nationally. We consider multiple components of the urchin removal process, including respect for Māori practice and traditions, large‐scale practicality, and ecological effectiveness. Urchin removal from urchin barrens is labour intensive but can promote rapid kelp recovery. However, without addressing the cause of sea urchin overpopulation (i.e. overfishing of sea urchin predators), kelp recovery is temporary as sea urchins will eventually return. Ongoing removals may provide longer‐term benefits but not a fully functioning and resilient kelp forest ecosystem. Therefore, urchin removal is best used as part of well‐planned, iwi‐supported and permitted restoration projects including marine protection. Finally, we caution that urchin removal should not detract or take away from restoration strategies to address the root cause of sea urchin overpopulation, particularly the rebuilding of predator populations.

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