By Lauren Sommer, Madeline K. Sofia, Rebecca Ramirez

Hoards of purple sea urchins have decimated kelp forests off the coast of northern California. The kelp here normally grows 30 to 60 feet tall, and is a key ecosystem for other plants and animals.

These sea urchins have always eaten some kelp — but usually not enough to hurt the entire forest. In the past they were kept in check by predators like the sunflower sea star. But there have been some big ecological shifts, exacerbated by climate change, that have led to an urchin explosion.

Scientists are tackling the problem on multiple fronts:

Manually removing sea urchins near healthy kelp and sending them to the compost heap.
Reintroducing natural urchin predators, like sea otters, in the hopes that they eat the urchins.
Putting them on the dinner table — getting people to eat the purple urchins.

This episode was produced by Rebecca Ramirez, edited by Geoff Brumfiel and fact-checked by Rasha Aridi.