Sea urchins play complex ecosystem roles as herbivores, but in the absence of their predators including sea otters and sunflower sea stars, urchin population explosions devastate kelp forests and the welfare of dependent species.
The welfare dimension of urchin barrens extends to all the species that depend on kelp forests - rockfish without shelter, marine mammals without food, invertebrates without habitat. The transformation from kelp forest to urchin barren represents a welfare collapse for an entire ecosystem community. Urchin welfare itself in barren zones is compromised - starving urchins in barrens lose their gonads and become physiologically empty, maintaining themselves through metabolic minimum while waiting for food. Restoring ecosystem balance through predator recovery and urchin harvesting addresses welfare at the community rather than individual level.