Last month’s news that the Army Corps of Engineers had pulled the permit for the Mid-Barataria Sediment Diversion was disappointing for many reasons.

But it may also be the final push the state needs to face critical coastal questions already fast approaching due to increasing climate impacts: Is it still possible to have a functional and habitable large coastal zone, or is it time to turn our efforts to a managed retreat south of U.S. 90 and reducing risks due to storm surge north of there?

The corps alleges the state “deliberately withheld information” during the permitting process.

The “whistle blower” is the Coastal Protection and Restoration Authority installed by Gov. Jeff Landry, which went to the corps with documents supporting its claims that the costs were underestimated by the previous administration of Gov. John Bel Edwards.

If proven, the corps’ claim will damage the plan’s scientific credibility.

Landry and team have been supporters of the project’s main opponents, some in the fishing industry. They oppose the plan because the amount of river water needed to move marsh-building sediment will drop salinity levels, pushing their brackish water target species southward. They would rather see the marsh rebuilt by just pumping mud from the river, a process that would not dramatically change salinities.

They say the more than $300 million set aside to help them make the transition is too little.

That’s a self-defeating position.

The dredge-and-fill method will not stop the increase in marsh salinity levels that have been climbing as the Gulf drowns the sinking marshes. Louisiana research shows that as brackish marshes become salty, the production of estuarine shrimp, oysters and fish species such as speckled trout and redfish falls. It’s why the daily limit for speckled trout in Texas and Florida has been three for years.

That’s also why we’ve spent millions over decades on projects bringing river water into those oyster grounds at the request of the industry. In fact, these opponents still want a diversion — but only large enough to help oyster reefs, not large enough to build and maintain marshes.

So, while today’s fishers push to make as much money as long as they can, their success likely means their grandchildren will have much less to fish for.

Finally, the project includes funds to build levees and raise roads in communities around the edge of the Barataria Basin. That could also be lost.

Killing the project largely over the economic hit to one stakeholder group would be foolish, especially after almost half of its estimated $3 billion cost has already been spent — and the state might have to pay back $1 billion of that.

Yes, the diversion is an experiment. But it’s one needed to verify what years of research suggest is the only sustainable way to maintain functional, habitable wetlands — even if they will need to be further north than they are today.

Which brings us back to that critical question facing the state: Is it already too late for most of the landscape south U.S. 90?

That´s because the major cause pushing the coastal zone to extinction — the fossil fuel emissions driving the record acceleration of sea levels — still has not been effectively addressed.

The average elevation of our coastal wetlands is 2.5 to 3 feet. The National Oceanic and Atmospheric Administration says the worst-case scenario for our coast in just 25 years is 1.5 to 2 feet of rise, not including the rate of subsidence. But with the Trump administration declaring war on all climate regulations, that worst-case has become more certain.

Is there enough time or sediment and funding to keep ahead of that pace over a large enough area of the coast to make a difference?

Or should we start moving communities south of U.S. 90, and begin building higher floodwalls north of there to reduce the risk of storm surge, and perhaps insurance premiums?

These questions must be addressed.