Kina have been a staple of the Māori diet for generations, but these voracious herbivores can wreak havoc on marine ecosystems. They primarily eat kelp, and where natural predators like snapper and crayfish have been depleted by fishing, kina populations explode, creating "kina barrens," vast stretches of bare rock stripped of vegetation. The loss of kelp forests dramatically reduces the ocean's capacity for nutrient cycling and carbon sequestration.

When kina are culled as part of restoration efforts (broken open underwater), their nutrients are recycled back into the local marine system. Harvesting them for food, however, removes those nutrients from the environment entirely.

In a balanced ecosystem, kina play a valuable role managing kelp growth. In an unbalanced one, they become destructive. Overpopulation in the Hauraki Gulf signals exactly that - an ecosystem out of balance.

To tackle the problem, an integrated management approach is underway: increased recreational catch limits, a new special permit system for large-scale removal, and the establishment of High Protection Areas to restore natural predator populations.