Saving the oceans is key to fighting the climate crisis, according to Ayana Elizabeth Johnson, a Brooklyn-born marine biologist and activist, who is a rising figure in the climate movement.

Dr. Johnson, 39, is the founder of Ocean Collectiv, a conservation consultancy, and of Urban Ocean Lab, a think tank, and speaks frequently at TED Talks, climate rallies and her salons at Pioneer Works in Brooklyn. Protecting the ocean is crucial for people at all economic levels, she said, not just bicoastal elites who look down their noses at plastic straws.

You have talked a lot about how the oceans are crucial in the fight against climate change. How so?

When people talk about the destruction of the Amazon, and how forests in general are the lungs of the planet, I always want to jump in and say the ocean is a huge part of that, too.

Phytoplankton — these tiny little plants in the ocean — produce a huge percentage of the oxygen we breathe, and the population of phytoplankton is declining. That should be a cause for concern for every single person.