Perched atop craggy bluffs in a beachside city north of San Diego, a railroad line offers passengers a sweeping view of the Pacific Coast. But the ground beneath it is crumbling.

No one denies the problem, but a fight over how to solve it highlights a broader challenge, and a worrisome reality, for California residents: how to adapt to climate change that threatens coastal living, a way of life that has long defined the state’s identity, from its economy to its culture.

The segment of track on the bluffs in Del Mar, Calif., connects San Diego to the rest of the state and the country, and is part of one of the busiest intercity passenger rail corridors in the nation. But the bluffs are eroding rapidly, and the track in some places is now only a few yards from the cliff edge.

Officials and residents in Del Mar and nearby communities broadly agree that the tracks need to be moved, but argue over where they should go. The debate has slowed progress, even as climate change accelerates the risks to the bluffs and the rail line.

On Friday, local representatives on the board of the county’s regional planning agency — the San Diego Association of Governments — voted to narrow the potential alternatives to four options, down from more than a dozen that were assessed in a recent report. But a final decision remains far off.

“It’s at a dangerous point, and with all the bureaucracy involved, it makes us wonder whether it will even be in our lifetime before it’s solved,” Barbara Myers, a former Del Mar school board member, said of the problem. She lives near the proposed location of a tunnel entrance to relocate the rail line, and she worries about toxic fumes or the possibility of street collapses.

With sea levels rising and stronger waves battering their shores, many other communities like Del Mar see a need to adapt, but are finding the options difficult.

Cliffside homes and apartment buildings teeter on the edge, some of them abandoned or demolished preemptively because of the threat of collapse from erosion. Infrastructure has taken a beating up and down the California coast: Sections of scenic Highway 1 have closed repeatedly because of landslides, and the Santa Cruz Wharf, a popular tourist attraction, was torn apart by towering waves in December. Communities are racing to protect shrinking beaches, reinforcing them with barriers and dredging sand from other areas in an effort to maintain and replenish them.

“The situation in Del Mar is a microcosm of a larger battle that’s unfolding,” said Charles Lester, a former official with the California Coastal Commission, a state agency that manages development along the coastline. He now directs the Ocean and Coastal Policy Center at the University of California, Santa Barbara. “What are we going to prioritize and try to maintain as these environmental changes happen?”

The Del Mar track is part of a 351-mile coastal rail corridor stretching from San Luis Obispo to San Diego. It is used by passenger, freight and military trains, including Amtrak’s Pacific Surfliner, whose name evokes the way sections of the route hug the coast. Millions of trips are taken along the route each year.

But the same coastal proximity that gives passengers scenic ocean views also makes the track vulnerable to erosion. Construction crews are now working on the fifth project since the early 2000s to stabilize the Del Mar bluffs, a $90 million effort that will, among other things, install additional support columns and retaining walls.

These projects are not a long-term solution. The rising ocean and erosion continue to pound the bluffs, leading to costly emergency repairs and repeated service disruptions. On average, the bluffs retreat a few inches a year, but there can be sudden collapses that chew away more than 20 feet at once. And not just in Del Mar: Erosion is also destabilizing parts of the rail corridor farther north, in San Clemente.

“Realistically, time is not on our side, with the acceleration of climate change,” said Fred Jung, who chairs the rail corridor’s board of directors. “We are forced to act right now.

City officials in Del Mar — a community of about 4,000 residents in an area of less than two square miles — have been talking for decades about moving the tracks off the crumbling bluffs. In 2017, the county planning agency completed a study outlining five possible new routes.

The idea gained momentum in 2022 when Gov. Gavin Newsom signed a state budget that allocated $300 million for relocating the tracks. In June 2024, the association of local governments announced that it had narrowed the options down to three, all involving inland tunnels.

The reaction was swift. Del Mar residents raised concerns about tunnel construction and operations beneath their homes, citing risks from vibration and pollution. People who lived near the entrance and exit points of the proposed tunnels worried that homes would be demolished.

A proposed route running through a lagoon was opposed by environmentalists because of how it might affect sensitive habitats. A route that would tunnel under the San Diego County Fair grounds and into neighboring Solana Beach met resistance from that city and from fair organizers.

And looming above the debate is the question of money. The project is expected to cost billions of dollars, and county voters rejected a half-cent sales tax increase in November that would have raised money for regional transportation and infrastructure projects, including the Del Mar track relocation.

In light of all that, the agency re-examined the issue, ultimately leading to the vote on Friday. Three of the options now on the table would move the line off the bluffs; a fourth would keep the track where it is, reinforce the bluffs and add a second track next to the existing one.

As required by state and federal law, the agency would also study a fifth option: no project at all.

The meeting, with two hours of discussion, grew emotional at times, as officials and residents voiced concerns about the proposed options. Mayor Terry Gaasterland of Del Mar abstained from voting.

The mayor said in an interview before the meeting that none of the remaining options is likely to satisfy everyone.

“We’re going to need to step back and minimize the sum total of the unhappiness,” she said. “And also spread it out.”

That debate was on display on a recent Saturday in Del Mar, as construction crews were working to stabilize a section of the bluffs supporting the tracks. Near the top, workers used excavators, a giant drill and other heavy equipment. In several areas, chunks of the bluffs had eroded and crumbled, sending dirt, rocks and vegetation tumbling down onto the beach.

Officials acknowledge that neither the current stabilization project nor emergency repairs offer a long-term solution to the challenges of the rising ocean and coastal erosion.

Jim Hindman, 64, a financial consultant, lives with his family just one house away from the bluff-top tracks. His voice was sometimes drowned out by the construction trucks that kicked up dust as they pulled in and out of his street, which ends at the tracks.

Mr. Hindman said the option to add a second track to the existing rail line would alter the character of his neighborhood and the bluff. He said the bluffs were a beloved community space where people gather to watch sunsets, spot whales and dolphins, and even celebrate weddings.

“Tranquillity by the sea? Not happening for the next couple of years,” he said, referring to the stabilization work and the potential for a tunnel project to follow.

Richard Sfeir, 66, has lived for three decades in Del Mar Heights, a San Diego neighborhood bordering the city of Del Mar. Many houses in the Heights perch high above downtown Del Mar along narrow, winding streets. One relocation proposal would route the tracks through a tunnel under the neighborhood, an idea that he called “crazy” because of its cost, timeline and impact on a protected environmental area.

But Mr. Sfeir, a businessman, said that something needed to be done.

“No solution is not an answer,” he said, “unless you get rid of the train, period.”