AEBR 365 Summarising and updating knowledge on the distribution of kina barrens in key regions of Aotearoa New Zealand

Spyksma, A.J.P. (2025). Summarising and updating knowledge on the distribution of kina barrens in key regions of Aotearoa New Zealand. New Zealand Aquatic Environment and Biodiversity Report No. 365. 45 p.

Kelp forests are highly productive ecosystems but are increasingly threatened by overgrazing from sea urchins, creating persistent “urchin barrens.”

In New Zealand, kina is the main urchin barren forming sea urchin, with fishing pressure on predators like snapper and rock lobster considered a key driver of urchin barren formation, particularly in northeastern New Zealand.

Despite widespread reporting of urchin barren habitats there has been no previous efforts to collate urchin barren distribution information across the country.

This study collated 27 data sources to produce a nationwide overview of urchin barren distribution and extent.

Barrens occur throughout the country, with large areas in northeastern New Zealand, Marlborough Sounds, Tasman Bay, Fiordland, and Stewart Island.

Additional aerial imagery mapping revealed barrens along ~36% of northeastern NZ’s rocky coastline, mostly on shallow, nearshore reefs, though estimates are conservative.

The resulting datasets provide a national starting point for future work and will help to inform management, track kelp forest recovery, and support mana whenua and community involvement in restoration and management initiatives.

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