Rising sea levels near Leeville, La., during the past 100 years have left this 1905 cemetery entirely underwater. (Tim Osborn/National Oceanic and Atmospheric Association)

Here on the side of Louisiana’s Highway 1, next to Raymond’s Bait Shop, a spindly pole with Global Positioning System equipment and a cellphone stuck on top charts the water’s gradual encroachment on dry land.

In 1991 this stretch of road through the marshlands of southern Louisiana was 3.9 feet above sea level, but the instrument — which measures the ground’s position in relation to sea level — shows the land has lost more than a foot against the sea. It sank two inches in the past 16 months alone.

That’s a problem because Highway 1, unprotected by levees, connects critical oil and gas resources in booming Port Fourchon to the rest of the nation.

Ten miles of the highway is now standing 22 feet above sea level on cement piles. But another seven miles is not, and if less than half a mile of this highway succumbs to the 14-foot storm surges expected in the future, the highway will need to be shut down, cutting off the port.

Local residents and business leaders are demanding that the federal government help pay to rebuild and elevate the remaining section of Highway 1, adding two miles to span the levees. Federal officials have provided scientific and technical expertise but will not contribute funding unless the state pledges to complete the road.

Louisiana says it doesn’t have the money.

The dilemma facing this important lowland road is one shared by communities across the country as climate change begins to transform the nation’s landscape. By 2030, many areas in the United States are likely to see storm surges combining with rising sea levels to bring waters at least four feet above the local high-tide line, according to a report released last Wednesday by Climate Central, a nonprofit research group. Nearly 2.6 million homes are on land that would be inundated.

The Obama administration is trying to plan for a country altered by shifts in precipitation, higher oceans and more intense periods of heat. It is rethinking infrastructure projects and creating a new plan for how to manage plants and wildlife in the face of global warming. Every agency is required to come up with a plan by June for how to adapt to climate change.

“It’s about how do we incorporate planning for a future that may look very different from the way the world looks today,” said Nancy Sutley, chair of the White House Council on Environmental Quality, who is spearheading the administration’s federal adaptation strategy.

Researchers at the National Oceanic and Atmospheric Administration, who started measuring tides in Louisiana in the mid-1800s, have analyzed the numbers for Highway 1, and they do not bode well. At today’s rate of sea-level rise — 9.24 millimeters a year — the road would be under water roughly 22 days of the year by 2030.

Windell Curole didn’t need NOAA’s number-crunching to tell him what’s coming. The 60-year-old general manager of the South Lafourche Levee District said he couldn’t see open water from this road when he was growing up. Now, it is in plain sight, just yards away.

The land is sinking, in part because engineers have redirected sediment flowing from the Mississippi River more directly into the Gulf of Mexico, improving navigation but no longer shoring up the wetlands.

And climate change is starting to make the problem worse. Not only is the sea rising as the ocean warms and expands, but heavier rainfall in shorter bursts is battering Highway 1.

Curole has devised a simple mantra that he believes will address sea level rise, as long as the federal government heeds it: “Elevation is the salvation from inundation.”

The road’s closure could have an economic impact far beyond the surrounding parish. The Department of Homeland Security completed a study last July that showed that a 90-day shutdown of Port Fourchon could translate into as much as $7.8 billion in lost national gross domestic product because neighboring ports could only replace 25 percent of the service the port provides, and it would come at a higher cost.

On a broader level, the Transportation Department is already analyzing how global warming will affect the gulf. Its preliminary assessment, issued in 2008, estimates that relative sea-level rise “will make much of the existing infrastructure” in the region “prone to frequent or permanent inundation.” It will complete a study this year examining climate impact on transportation infrastructure in Mobile, Ala.

Tim Osborn, NOAA navigation manager for the central Gulf Coast, describes the Highway 1 predicament as “a way we can look at climate change as having near-term impacts that are national in scope and impact.”

A group of area residents and businesses, dubbed the LA 1 Coalition, have spent the past 15 years lobbying for funding to build the highway well above any possible storm surge or sea-level creep. Replacing the 10 miles closest to the port cost $371 million, paid for with local, state and federal funds plus a new bridge toll.

“We can’t raise any more money locally,” said Henri Boulet, the coalition’s executive director. “We’re maxed out, financially.”

But the Transportation Department has so far rejected funding the second phase of Highway 1’s elevation. The department is not only deluged with requests for its $2.6 billion discretionary grant program, it can only support projects that build completed roads, so officials have said they could likely provide $20 million if the state agrees to fund the rest of the $320 million project over the next four years. That would consume about a third of Louisiana’s total construction budget in a single year.

Beth Osborne, deputy assistant secretary for transportation policy, said the Obama administration has pressed to expand the grant program but has not gotten its full funding request. “Frankly,” she said, “there’s not much money to go around.”

Many Louisiana officials and residents feel as if they’re being forced to fend for themselves. Curole said local residents constantly reassess whether it makes sense to take unusual measures to stay and continue exploiting the region’s productive coast, and right now it still does.

“Who benefits from that hard work?” he asked. “Everybody.”

The LA 1 Coalition is now trying to focus on raising $45 million to elevate a shorter segment of the road, three-quarters of a mile long, with a combination of state funds and $6.6 million in donations from businesses in Port Fourchon.

One Louisiana firm has done more than any other to help the region adapt: after completing a climate analysis of the region, Entergy has embarked on a series of projects including upgrading its transmission lines to Port Fourchon and moving poles and wires right next to Highway 1, where there is a sliver of land to support them.

Entergy’s chief executive, Wayne Leonard, who fought unsuccesfully for national limits on greenhouse gas emissions, said executing these projects can be challenging because he needs to justify the expenses to ratepayers.

“If all the costs are today to do climate adaptation but you don’t see the benefits for fourteen, fifteen years, then it’s zero benefits, all costs,” he said.

And even all the steps Entergy is taking, Leonard said, may not keep the port above water.

“When we’re done with this, I can assure you the lights will still be on,” Leonard said. “I can’t say the port will be there.”