In June 2013, starfish on the western coast of North America started wasting away. At first, their arms curled from the tips, and they tied themselves into pretzel-like knots. Their bodies deflated. White festering sores appeared on their flesh. As the lesions spread, their flesh rotted away and their arms fell off. Within days, healthy animals had disintegrated into mush.

This condition, known as sea star wasting syndrome (SSWS), was recorded as far back as the 1970s, but the scale of this recent event is unprecedented. It has hit at least 20 species all along the Pacific, from Alaska to California. In less than a year, huge, thriving populations have completely wasted away.

As the stars blinked out, scientists compiled