– Decades of shortsighted decisions by industry and government have put the Mississippi River’s future at risk, and degradation at its southern Louisiana delta is contributing to “the greatest land loss on the planet,” a five-state environmental coalition warned Wednesday.

As much as $50 billion will be needed to secure Louisiana’s port system, but “there is no hope in the current budget of the United States. Zero,” said Democratic Sen. Mary Landrieu of Louisiana, who addressed a diverse group of political, environmental and private-sector leaders at a conference in Washington on the river’s future.

Despite a $14 billion federal infusion after Hurricane Katrina ravaged the state in 2005, Landrieu said, southern Louisiana is losing land masses the size of the nation’s capital to the Gulf of Mexico every year.

“New Orleans is going to be very close to being under water,” she said. “If you don’t have wetlands around you and a healthy delta, you just can’t live there.”

The conference, sponsored by America’s Wetland Foundation, laid out the findings of forums attended by more than 400 government, nonprofit and private-sector leaders over a 12-month period in Minneapolis, Chicago, St. Louis, Memphis, Tenn., and New Orleans, all cities that are in states whose economies depend heavily on the river.

Attendees spoke of galvanizing a coalition of mayors up and down the river to muster enough clout to win a massive federal financial commitment to save the river and the Gulf Coast, especially in southern Louisiana and southwestern Mississippi.

Among the findings from the forums:

– The construction of locks and dams along the river to control flooding and facilitate shipping has resulted in a glut of silt along its northern stretches, reducing the flow of crucial, nutrient-containing sediments to the delta and impairing the growth of wetlands that shield the coast.

– Agricultural runoff has polluted the river with high levels of nitrogen and phosphorus that are running into the Gulf of Mexico, contributing to an oxygen-depleted zone that can’t support marine life.

– Levees along the river have severed its connections to floodplains, reducing their water-retention capabilities and exacerbating floods and droughts.

However, building a coalition to address those and other threats has been difficult because interests are localized, various regions bear the consequences of inaction unequally and the states have lacked a systemic view to motivate action, the forum found.

Environmentalists back a plan to divert the silt that’s flowing beyond the Outer Continental Shelf back to shore, but they need money.

Landrieu has proposed allotting a portion of the federal royalties that oil and gas companies pay for Gulf of Mexico mineral leases to address the problem, perhaps $2 billion annually.

R. King Milling, the wetland foundation’s chairman, said after the meeting that he thought mayors in cities along the river “are beginning to coalesce” and that trade groups “are beginning to panic” over the impact of droughts and floods.

Ultimately, he told McClatchy, he hopes that a broad coalition will “come to Washington and say, ‘Look, we have a crisis. And you’ve forgotten about it.’ ”