And now for something completely frightening.

The Louisiana coast is rapidly sinking into the sea. There are efforts and plans to move sediment around to save New Orleans and some pipelines and fishing grounds, but much of the Delta is doomed (and the planned fixes are hugely expensive, and Louisiana is a  poor state).

Southeastern Louisiana might best be described as a layer cake made of Jell-O, floating in a swirling Jacuzzi of steadily warming, rising water. Scientists and engineers must prevent the Jell-O from melting — while having no access to the Jacuzzi controls.

The problem is human-made. Over the last 80 years, Louisiana’s coast has been starved of sediment by river levees and eviscerated by canals dredged for oil and gas extraction. Now, southeastern Louisiana is sinking at one of the fastest rates on the planet as the Gulf is rising.

Already, 2,000 square miles have sloughed into the Gulf. Without action, the state could lose another 1,750 squares miles over the next 50 years.

If that happens, in 70 years New Orleans could be left on a razor-thin sliver of land extending into the open Gulf, battered by storms rolling over the watery graves of unprotected communities.

The economic effects will reverberate across the nation as the seas swamp half of the nation’s refineries and pipelines that transport 30 percent of the country’s oil and gas. The country’s largest port, an economic door to 31 states, would be vulnerable to run-of-the-mill tropical storms, causing shutdowns that cost the nation’s economy an estimated $300 million a day.

Not a trivial problem.

Most of us have known at least some of that ever since Katrina, but it’s easy to lose sight of just how drastic the situation is.

And the proposed fixes are no guarantee of anything themselves, because any fix they can do will have consequences elsewhere and it’s a mammoth engineering task to figure all that out. Sending a box to Mars looks easy in comparison.

“My concern is that a lot of people think if we just turn the river loose, it will just fill in all those holes we’ve created in the delta,” said Roberts. “Well, certainly it’s not as simple as punching holes in the levees.”

Every diversion project is a move in an ongoing chess match with nature. Each one faces different sets of variables and constraints, and engineers are struggling to anticipate the consequences of each step they take.

“Everything you do at one point on the river — anything you take out or put in — will have an effect on the rest of the river,” said Alex McCorquodale, a University of New Orleans researcher working on a study to determine how much sediment is in the lower Mississippi.

It’s a matter not so much of finding a fix as of juggling bad consequences in different places, or even the same places.

Considering how much remains unknown, a few scientists ask why Louisiana has staked so much on diversions. They worry the state could waste its last chance for the coast on a technique they believe poses its own habitat threats and exists only on computer models.

Gene Turner, a distinguished LSU coastal researcher, points to studies that show high levels of nutrients from fertilizer upstream can cause wetlands loss by damaging plants in areas with high organic soils. He is concerned that the state doesn’t have a backup plan if its computer models are wrong.

“Every building code requires a fire exit, and right now this plan doesn’t have one,” he said. “Saying, ‘This is going to work’ isn’t a backup plan, not when you’re doing something that has never been done before, except on computers.”

Turner has the minority view in the coastal scientific community. Nonetheless, the state coastal agency has asked the Water Institute of the Gulf to gather a panel of outside coastal experts to look into those questions.

And then, all this depends on climate predictions, and there’s reason to think current predictions could turn out to underestimate the rate of climate change.

So read the whole thing; it’s an education in itself.