What is an urchin barren?

A An urchin barren is an area of underwater kelp forest that has been over-grazed by sea urchins – spiny echinoderms that live in colonies at the base of the plants and munch avidly on their stems. As keystone predators, sea otters usually keep urchin populations in check. Declines in their numbers directly correlate with increased ‘barrens’.

Giant kelp is a form of brown macroalgae. It typically extends from a holdfast on the seabed to the water surface tens of metres above, while other species extend a few metres above – or lie along – the seabed. Kelp’s dense underwater towers are of huge ecological importance, offering food and shelter to a vast range of marine species, as well as absorbing considerable amounts of CO .