Any astronaut can tell you you've got to do everything you can to learn about your life support system and then do everything you can to take care of it.

Never before have we known what we know.

Many of us ask what can I, as one person, do, but history shows us that everything good and bad starts because somebody does something or does not do something.

There are now more than 4,000 places in the sea around the world that have some kind of protection. The bad news: You have to look hard to find them. What you find instead is destructive fishing, mining, gas and oil exploration.

We humans have this idea that the ocean is so big, so vast, so resilient that it doesn't matter what we do to it. That may have been true 1,000 years ago. But in the last 100, especially the last 50 years, we have destroyed the assets that make our lives possible.

I'm haunted by the thought of what Ray Anderson calls 'tomorrow's child,' asking why we didn't do something on our watch to save sharks and bluefin tuna and squids and coral reefs and the living ocean while there still was time. Well, now is that time.

The value of sharks' lives is now widely understood to be more important than their value as products. And when you have sharks in an area, it's a sign of good health. They're top predators, which means they feed on old, sick, and slower fish, keeping an entire population healthy.