Cynthia Barnett is an environmental journalist who has covered water and climate stories around the world.

Her latest book "Voice of the Sea: Shells and the Fate of the Sea" tells the cultural and natural history of shells and the mollusks that make them. These creatures have existed on Earth for much longer than humans and have helped shape our world.

Cathy Carter of WUSF recently had a conversation with Barnett about seashells on our oceans.

Cynthia, one of your comments on shells is that people really like their beautiful appearance. But we did not think too much about their inner life.

That's right. These are all magical animals. I began to think that shells and their makers are a good metaphor for how we view the ocean itself, right? We regard the ocean as the beautiful background of life, not the source of life. And I think the ocean is so huge and beautiful that it is difficult to understand what is happening under the waves, especially when it comes to something invisible, such as ocean acidification.

Yes, so what does the shell tell us about our ever-changing ocean?

As a result, the shells are beginning to signal to us that the ocean is acidifying, and the ocean has absorbed nearly a third of the extra carbon dioxide emitted by humans into the atmosphere. They absorb more than 90% of the extra heat, which increases with the increase in carbon emissions. For mollusks, certain parts of the ocean have become too warm. As far as the shell itself is concerned, molluscs use the minerals in the surrounding seawater to build the shell, mainly calcium carbonate. These additional carbon emissions make it difficult for mollusks to absorb carbonates in the surrounding ocean. This makes it more difficult for molluscs to build their shells.

So, it sounds like the shell provides some kind of warning signal.

Yes, I began to think that shells and their makers are the greatest fact checkers in the world. There is an amazing paleontologist at the University of South Florida in Tampa, who is very helpful to this book. His name is Greg Herbert, and he did some fascinating analyses off the coast of the Gulf of Mexico. He compared the shells that exist now with those 50 years ago. His research shows that the number of marine molluscs is indeed not as large as in the United States in the middle of this century. So it’s not just climate change, overfishing or toxic algae, it’s really our way of life and our countless impacts on the ocean.

So, given our knowledge of the ocean and the pressure on shells, is it okay to pick up shells on the beach?

I think this is a good question. I think it fully illustrates our ever-changing world, you know, sometimes you feel guilty and even really enjoy the things you liked when you were a kid. Even the enjoyment of seafood has become even more worrying for me. Now, because of my knowledge of the ocean, I have made very different choices for seafood. I think this is the same as collecting shells. But I still think it is very important to experience the fun of picking shells, especially for children. In fact, finding your own empty shells on the beach is more sustainable than buying tropical shells in a shell store, which may import shells from Indonesia or other endangered animals. So, I think picking up local shells is a good thing and a good memory of the beach.

Cynthia Barnett (Cynthia Barnett) will discuss and sign The Sound of the Sea at Tampa Bay Watch (3000 Pinellas Bayway S, Tierra Verde) on July 11th at 4pm on July 20th. 30 points.