How sea urchin population explosions following otter and sunflower sea star decline devastate kelp forest ecosystems.
Sea urchin overabundance following predator collapse represents a cascade of ecological welfare harm affecting thousands of species dependent on kelp forests. When urchins lack predators, they overconsume kelp until nothing remains, converting diverse, three-dimensional ecosystems into bare rock barrens. The welfare consequences extend from the disappearance of fish nursery habitat to the loss of foraging opportunities for marine mammals. Restoring urchin predators — through sea otter reintroduction and disease-resistant sunflower sea star recovery programs — addresses the ecosystem welfare problem at its source. Manual urchin culling provides interim management.