Populations of purple sea urchin have exploded up and down the west coast, decimating kelp and crowding out other marine animals. In a recent count of one Oregon reef, the population of purple urchins was 350 million, an increase of 10,000 percent over the last five years. Shellfish biologist Scott Groth with the Oregon Department of Fish & Wildlife explains the factors that have led to this situation. We also hear from Tom Ford, the executive director of The Bay Foundation, about efforts to remove urchins and restore kelp on the southern California coast.