The railroad tracks that slice through downtown Freehold, N.J., used to be lined by dozens of men, waiting for work. Each morning, the men — day laborers, almost all from Latin America and undocumented — would be scooped up by local contractors in pickup trucks for jobs painting, landscaping, removing debris.

In recent weeks, the tracks have been desolate. On a gray February morning, a laborer named Mario, who came from Mexico two decades ago, said it was the quietest he could remember.

“Because of the president, we have a fear,” said Mario, 55, who agreed to be interviewed on the condition that only his first name would be used because he is undocumented. His two sons are also in the United States illegally; one works in paving, the other in home construction. “We are in difficult times,” he said.

This scene has been playing out on the streets of Freehold, on the farms of California’s Central Valley, in nursing homes in Arizona, in Georgia poultry plants and in Chicago restaurants.

President Trump has broadcast plans for a “mass deportation,” and the opening weeks of his second term have brought immigration enforcement operations in cities across the United States, providing a daily drumbeat of arrests that, while so far relatively limited, are quickly noted in group chats among migrants.

Fear has gripped America’s undocumented workers. Many are staying home.

The impact is being felt not only in immigrant homes and communities, but also in the industries that rely on immigrants as a source of willing and inexpensive labor, including residential construction, agriculture, senior care and hospitality. American consumers will soon feel the pain.

“Businesses across industries know what comes next when their work force disappears — restaurants, coffee shops and grocery stores struggling to stay open, food prices soaring, and everyday Americans demanding action,” said Rebecca Shi, chief executive of the American Business Immigration Coalition.

An estimated 20 percent of the U.S. labor force is foreign born, and millions of immigrant workers lack legal immigration status.

Hundreds of thousands more have been shielded from deportation and have work permits under a program called temporary protected status, offered to nationals of countries in upheaval, which has enabled corporate giants like Amazon and large commercial builders to hire them. But Mr. Trump has already announced that he will phase out the program, starting with Venezuelan and Haitian beneficiaries.

Refugees from around the globe, who have settled in the United States after fleeing persecution, have supplied a steady pipeline of low-skilled labor for poultry plants, warehouses and manufacturing. But that pipeline could dry up since Mr. Trump shut down the U.S. refugee program. Last month, a federal judge restored it temporarily while a lawsuit is pending, but the program remains at a standstill and no refugees are arriving.

The White House did not respond to questions about the strategy of deportations and how the Trump administration envisions filling the gaps left behind by the immigrant work force.

Leaders of industries that are the most exposed warn that the impact will be widespread, with far-reaching consequences for consumers and employers.

Kezia Scales, vice president at PHI, a national research and advocacy organization focused on long-term care for older adults and people with disabilities, said her industry was already facing a “recruitment crisis.”

“If immigrants are prevented from entering this work force or are forced to leave the country by restrictive immigration policies and rhetoric,” she said, “we will face systems collapse and catastrophic consequences for millions of people who rely on these workers.”

Warning of Higher Costs

In construction, up to 19 percent of all workers are undocumented, according to independent estimates — and the share is higher in many states. Their contribution is even more pronounced in residential construction, where industry leaders have warned of an acute labor shortage.

“Any removals of construction workers is going to exacerbate that problem,” said Nik Theodore, a professor of urban planning and policy at the University of Illinois Chicago. “Inevitably, it will slow the work, which leads to cost increases, because of the production delays.” This would have a profound impact on the construction industry and everybody involved, from developers to private homeowners, Mr. Theodore said.

In commercial construction, a tightening labor market would raise costs because of upward pressure on wages, said Zack Fritz, an economist with Associated Builders and Contractors, a national construction trade association.

The group’s chief executive, Michael D. Bellaman, said he welcomed many aspects of what he deemed Mr. Trump’s “deregulation, pro-growth agenda.” But he and others in the industry also called for an overhaul of the immigration system, including by expanding work visas.

Commercial building relies on many workers with temporary protected status, Mr. Bellaman said; some have been in the industry for decades.

The mayor of Houston, John Whitmire, said people who think his city and the country can thrive without the labor of undocumented immigrants “don’t live in the real world.”

“You know who’s paving our roads and building our houses,” said Mr. Whitmire, a Democrat.

Challenges in Elder Care

The senior care industry faces a similar challenge: growing demand for workers, and not enough native-born Americans to do the work. Those jobs have increasingly been filled by immigrants with varying legal statuses.

Adam Lampert has spent 15 years in the industry in Texas, mainly managing care for the parents of baby boomers. The business is thriving — and a silver tsunami is on the horizon, he warns: The number of adults 65 or older in the United States totaled 60 million in 2022, and is projected to exceed 80 million by 2050.

“Baby boomers are yet to wash through the system, and they will be a full new generation we will have to address,” said Mr. Lampert, the chief executive of Manchester Care Homes and Cambridge Caregivers, based in Dallas.

Some 80 percent of his caregivers are foreign born. “We don’t go out looking for people who are immigrants,” he said. “We go out hiring people who answer the call — and they are all immigrants.”

Everyone he hires has permission to lawfully work in the United States, he said, but if the mass deportations promised by Mr. Trump materialize, recruitment will become tougher in an industry already struggling with it.

There are five million people working directly with clients in what is considered the formal senior care industry, made up of those who can legally hold jobs in the United States.

In New York, two-thirds of those working in homes are foreign-born, as are nearly half in California and Maryland. Countless others take part in the vast gray market, potentially worth billions of dollars, employed by families who hire in-home aides, many of them undocumented, by word of mouth or online.

The caregivers in private homes support seniors with essential activities of daily life, helping them eat, dress, bathe and use the toilet. They escort them to doctors’ appointments and manage their medications. It is low-skill, low-pay work, but requires a certain temperament, physical strength and patience.

If tens of thousands of undocumented caregivers were deported, there would be more competition for fewer caregivers, experts say. The cost of in-home care would climb.

Often green card holders and U.S. citizens have undocumented family members, and these mixed-status families have been under strain as immigration crackdowns have intensified.

Molly Johnson, general manager of FirstLight Home Care, a licensed agency in California, has rapidly expanded her roster of caregivers to meet galloping demand since starting the business five years ago. All her workers have passed background checks, she said, and are U.S. citizens or legal permanent residents.

But recently, one of the standout caregivers, a native-born American, suddenly quit because her mother was detained by immigration agents. The person she cared for was distraught.

“Unfortunately, we are going to be seeing more of this trickle-down effect,” Ms. Johnson said. “If it’s not our caregiver, it’s their loved one impacted by enforcement actions.”

A Test for Growers

During the Covid-19 pandemic, the immigrant men and women employed at Deardorff Family Farms in Oxnard, Calif. — and across the country, in vast fields and food processing plants — were anointed “essential workers” by the government.

Like other growers, Tom Deardorff, who runs the vegetable farm, printed cards for his workers to show law enforcement officers, in case they were stopped on their way to the fields, declaring that the Department of Homeland Security considered them “critical to the food supply chain.” Their immigration status was not of concern.

“These people have come into our country to do this work,” said Mr. Deardorff, a fourth-generation grower. “We owe them not just ‘thank you.’ We owe them the common decency and dignity to not be threatened by government draconian penalties.”

Now, with Mr. Trump in the White House, many immigrants who harvest strawberries, vegetables and citrus in this agriculture-rich stretch of Southern California face possible detention and deportation.

The U.S. farming sector has suffered a labor shortage for decades. Immigrants, mainly from Mexico and Central America, have filled the void: Farmers say they cannot find American-born laborers to do the strenuous work. More than 40 percent of the nation’s crop workers are immigrants without legal status, according to estimates by the Department of Agriculture, yet many have lived in the United States for decades.

“The argument that some have made, from time immemorial, is that people will do these jobs if all the immigrants leave,” said Janice Fine, a professor of labor studies and employment relations at Rutgers University. “But there is no guarantee that employers will raise wages or improve working conditions.”

She said there had been a “misunderstanding of the labor market.” The reason American citizens aren’t in the agriculture sector — or elder care, or residential construction — isn’t solely about money, she said. These jobs, she said, “are low-wage, low-status, high-exploitation unless workers organize unions.”

A three-day crackdown in California’s Central Valley in January, before Mr. Trump took office, showed the potential effects of large-scale enforcement in farming areas. Absenteeism soared after Border Patrol agents conducted sweeps in Bakersfield. They stopped and arrested people at a Home Depot, at gas stations and along a heavily trafficked route to farms, according to the Nisei Farmers League, a grower association.

Some 30 to 40 percent of workers failed to report to the fields in the days that followed, according to the league, which represents about 500 growers and packers.

Gregory K. Bovino, a Border Patrol chief in Southern California, called the operation an “overwhelming success” that resulted in the arrests of 78 people in the country illegally, including some with “serious criminal histories.” Farmworker advocates said many others without criminal records had been rounded up, too.

Bracing for More Raids

Migrants and advocacy organizations are bracing for more raids.

In Princeton, N.J., one rainy February evening, around a dozen day laborers gathered for a meeting with Resistencia en Acción, a New Jersey group focused on immigrant workers, part of a sprawling organization called the National Day Laborer Organizing Network.

The workers had different immigration statuses — some had temporary protected status or other forms of protection; others were undocumented. They worked as drivers and pavers, in restaurants and in mechanic shops. One man, who worked in a window factory, said he was terrified that federal agents would come to his workplace, where dozens of other Latin American immigrants toiled. Others said they had been working fewer hours in recent weeks, out of fear.

One man, who said he worked chopping fish, fruits and vegetables for a small grocery store, wondered aloud: “What white person is going to do these jobs?”