Will our slice of the Pacific Ocean still be healthy in 2050?

Ask Ben Lyles, a former biology teacher, if the ocean off the coast of Southern California will still be a good place to swim or surf in, say, 2050, and he answers by saying how much he wants to teach one of his great-granddaughters to fish.

Two hurdles, he said, stand in his way: “Time and greed.”

The time thing is clear. Lyles is 88. And while he’s still vibrant (he spoke during a sunrise “power walk” on a bluff overlooking the beach at Crystal Cove State Park), he’s also only...