Missing Protectors

Kelp forests are some of the most important habitats in coastal waters around the world. They provide breeding grounds for fish and shellfish, and protect juveniles from predators. They absorb carbon dioxide, which helps control climate change. But the forests are vanishing—they’re being devoured by sea urchins. In part, that’s because the forests are losing their protectors.

In New Zealand, one of those protectors is rock lobsters—known locally as kōura. But they’re vanishing, too, as the result of overfishing.

Kōura are different from the lobsters in the United States—they don’t have the big claws, and their bodies are spikier. Sea urchins are among their favorite prey. So a healthy population keeps the urchins in check—and the kelp beds lush.

Much of New Zealand is bordered by big beds of kelp. They’re populated by two main species. One of them is the fastest-growing organism on Earth—it can grow by more than two feet in a single day. But warming oceans have damaged some of those beds. Sea urchins like the warmer waters, so they move in and feast on the weakened kelp.

Commercial fishing operations began harvesting huge numbers of kōura in the early 1900s. Today, there are some restrictions—including complete bans in marine reserves. Even so, the population continues to drop. With fewer kōura, urchins not only devour the kelp, they can block any recovery—unmolested by the one-time protectors of the forests.