Carl Hodges holds a salicornia plant. Salicornia packs as much high-quality vegetable oil per acre as soybeans, making it an ideal biofuel crop.
Carl Hodges holds a salicornia plant. Salicornia packs as much high-quality vegetable oil per acre as soybeans, making it an ideal biofuel crop. - 

SAM EATON: Big ideas, the kind that change the world, often come from the oddest places.

For atmospheric scientist Carl Hodges that place was 6,000 feet above Mexico's coastal desert, south of the Arizona border. And his idea, if it works, could stop one of global warming's most serious threats: Rising seas.

CARL HODGES: Alfredo, we're gonna make a pretty sharp turn and we're going to follow that water inland, that river.

We fly along the coast of the Sea of Cortez and then bank inland. In recent years entrepreneurs have transformed the dry desert below us into a network of saltwater lakes so large they're visible from space. They were built to grow shrimp.

But the source of Hodge's inspiration isn't the shrimp farms, it's the giant man-made canal that supplies them with a constant river of seawater.

HODGES: That one pumping station with four pumps is as big as many rivers in the world.

And that's what gave Hodges his "eureka" moment.

HODGES: These shrimp farms between here and Guaymas, which is only 100 miles to the south, pump more than 20 percent of the ice melt of the Antarctic.

Hodges started crunching the numbers and came up with the total volume of water flowing from the world's thawing icecaps and glaciers.

HODGES: Four o'clock in the morning I'm at, "Jesus, that's not very much." I mean, I had this image of what it was and how much the sea level was rising. And I knew there was thermal expansion and all this, and that's not very much. And then I realized, my God, we can stop sea-level rise.

Especially with the right profit motive.

Near the Mexican fishing village of Bahia de Kino, Hodges is experimenting with what he hopes will become the world's next big cash crop. What look like rice fields stretch in every direction, turning this patch of desert scrubland into a green oasis.

HODGES: This is Salicornia bigelovii. To be slightly modest, which I have propensity not to do at times, it's probably the reinvention of irrigated agriculture.

That's because it doesn't use a drop of fresh water. The only thing these plants need to grow is the desert sunshine and a daily soaking of seawater.

HODGES: We'll pick out one that we want to play with, and we'll pull it up. OK, here are seeds in the center, and each section like a pinwheel with eight areas will become a seed.

Those seeds are key to Hodges' vision. They pack as much high-quality vegetable oil as soybeans, making salicornia an ideal biofuel crop -- and a highly profitable one. Especially if the fertile effluent from those shrimp farms we saw from the air is used as the irrigation source.

Today that water flows back into the Sea of Cortez, causing huge dead zones along the coast. But it's not the environmental damage that bothers Hodges. It's the wasted opportunity.

HODGES: Why not you take it inland, green the earth, make some money, and give a whole bunch of people jobs?

But for any of this to counter rising seas another step has to be taken. All that seawater pumped inland has to stay inland -- forever. And this is where the big science comes in.

Hodges drives me into the heart of the desert. We pass miles of abandoned farms. Agriculture is in retreat here as the vast underground aquifer has slowly been pumped dry.

We stop at a deserted farmhouse at the side of the highway. Hodges is trying to get a sense of how far the water table has dropped. And an old well at the back of the house could hold the answer.

HODGES: OK, what I'm going to do is I'm going to drop a rock. Based on what we've been able to put down there with string we don't think there's any water. But I'm gonna listen really close. The rock is now going down, going... I didn't hear anything that sounded like water.

This well, and the hundreds of others like it, supply crucial data points for the most controversial part of Hodges' plan. He wants to use the drained coastal aquifers as giant storage tanks for the world's brimming oceans.

Hodges says the process is not only safe, it would actually boost the remaining freshwater supply further inland. And he's got the science back it up.

The main obstacle, he says, isn't whether or not it can be done. It's whether the planet's 6.5 billion people are willing to think a little bit bigger when it comes to adapting to a warmer world.

HODGES: We always have choices. One of my favorite authors is Robert Grudin, and he said true freedom, when given a choice between A and B, is to create C. That's what we're doing.

In Sonora, Mexico, I'm Sam Eaton for Marketplace.

Follow Sam Eaton at @eatonsam