When Bren Smith was 14, he dropped out of high school and went to sea.

Smith was born and raised in a small fishing village called Petty Harbour, in Newfoundland, Canada. Petty Harbour is 700 miles east of Maine, and it juts out into the Atlantic like the herald of the entire North American continent. It's so tiny that it's basically just a few saltbox houses painted in bright colors, helping fishermen find their way home in the fog.

Smith worked on boats for years, and he loved his job.

"That's where I want to spend my days," he said. Smith is now in his mid-40s. Pictures of him show a lean, bald man with varying stages of beard. He says that like a lot of fishermen, he fell in love — not so much with the ocean itself, but with the feeling of working on the ocean.

"Farming the ocean is really meaningful work," he said. "There are certain jobs, traditional jobs, like coal workers who help power the country, steel workers who helped build the country, and fishermen and farmers, who help feed the country — there's real satisfaction and meaning that comes with that."

But under the ocean's surface, things weren't going too well. One day, the jobs seemed to just disappear.

The Grand Banks, off the coast of Newfoundland, are some of the richest fishing grounds in the world. And at some point, they must have seemed endless. In 1968, fishermen brought home over 800,000 tons of cod from those waters, for instance. That's more than the weight of eight full aircraft carriers.

But starting in the 1970s, the cod's numbers started to fall. Overfishing, trawling, dragging, and government mismanagement destroyed the cod stock. And after centuries of being one of nature's greatest wonders, in 1992, the Canadian government told Newfoundland's cod fishermen that they couldn't go out fishing anymore. There were essentially no cod left to catch.

As the Earth changes, jobs go away.

The ban on cod fishing snapped the economic backbone of hundreds of rural Newfoundland communities. Over 40,000 people lost their jobs. Some fishermen got government assistance or found new jobs on land, but Smith says the real shock ran much deeper than that.

There's a famous story in Newfoundland, Smith said, about a former fisherman who got a government buyout — a check to beach his boat, essentially — "and then every morning he drives down to the dock at 5 in the morning, with his brand-new truck he bought with that government check, and drinks himself to death looking out over the ocean, wishing he was working at sea."

This tragedy wasn't about money, you see. It was never about the money. Instead, losing that job meant losing part of their culture. It meant losing a sense of meaning.

Smith had been working elsewhere, but watching his hometown's collapse affected him. So Smith changed jobs, looking for work that was truly sustainable. Over the years, he tried a bunch of different things, but it never seemed to work out. Hurricanes Irene and Sandy put an end to his oyster farming idea, for instance.

Realizing that he needed to adapt, Smith decided to invent a new job altogether. Now, he's what he calls a "3D ocean farmer."

Smith owns and runs the Thimble Island Oyster Company in Connecticut, but oysters are only part of what he does. He's actually growing an entire forest underwater.

From the shore, Smith's farms don't look like much — just a few buoys bobbing up and down in the surf. But running beneath those buoy are long ropes from which dangle kelp, seaweed, mussels, and scallop nests. Below, resting on the sea floor, Smith has cages full of oysters. Clams live in the mud below those cages. And holding it all together are heavy, hurricane-proof anchors studded along the edges.

The result looks a lot like an underwater garden or kelp forest.

These 3D farms might actually be one of the most sustainable forms of agriculture in the world.

Unlike many common foods, Smith's seaweed and shellfish need no land, fresh water, or fertilizer. Kelp also grows extremely quickly.

And while seaweed is largely absent from the American diet, it's a really common food in other parts of the world, especially in Asia. Many American chefs are now testing it in their menus.

There are secondary benefits to the environment from the underwater farms as well. The kelp can trap carbon, removing it from the atmosphere and reducing the impact of global warming. Shellfish can help filter pollutants and excess nitrogen out of the water. The farms can even act like coral reefs, providing a hiding place and habitat for other creatures.

"The best fishing in the entire area is surrounding our farms," said Smith. "We have seals, we have ducks, we have sea horses — all these different species that are returning to our areas."

Because of what he's learned, Smith is now helping other fishermen start underwater farms too.

In addition to running his farm, Smith is in charge of GreenWave, a nonprofit that helps other farmers start their own 3D ocean farms. They have a blueprint for 3D farmers to get started as easily as possible. The GreenWave team also helps farmers evaluate locations and feasibility, get permits, and set up and expand their farms.

GreenWave is still a small operation — just a handful of people working toward something they believe could change the world. But what they're doing is actually working, and they've even been awarded the 2015 Buckminster Fuller Prize for ecological design. They've also just opened a big new project, a seaweed hatchery, to help farmers supply other farmers with seed.

Ultimately, Smith thinks we could build a whole new food system using 3D ocean farms.

He wants to break the logic that leads to big, industrial farms on land and create a whole new kind of food industry — one that has sustainability and food justice at its heart.

For example, GreenWave doesn't charge farmers extra for seed, and it encourages farmers to only use local species. A farm in California won't grow the same kind of seaweed and shellfish as a farm in Maine, a practice that can help keep our food system safe from climate change and disease. And Smith says the minimum wage in their processing plants starts at $15 an hour.

There are still a lot of hurdles, of course. Americans still aren't known for their love of seaweed. And it seems like GreenWave will need to build a lot of their infrastructure from scratch, too. But these obstacles do not seem insurmountable.

To me, the most encouraging part of this story is that we can revive the kind of job Smith fell in love with.

Sometimes it's easy to think of conservation like a museum, trying to capture the world in some unchanging, static preservation, like a bug under glass.

But that's not what Smith is interested in. For him, the question has always been as much about economics as environmentalism. The question isn't "How do we make sure things never change?" The question is "How do we prepare for the future?"

"We need to build a new economy, we need to feed people, we need to create jobs, and we have to give people meaning if we're going to save the planet," Smith said. He finds that the work on his farm still has that meaningful heart that propelled him to the ocean as a teen.

As Smith put it, we have to find the space for "jobs we can still sing songs about." And we can.

Whether that's transitioning coal miners to solar power-plant workers, oil drillers to dam workers, or fishermen to ocean farmers, we can reinvent the old industries into the new.

We can still have jobs you fall in love with.