OXNARD— Ana Rosa Perez emigrated from central Mexico to work in Oxnard’s strawberry fields more than 10 years ago. She remembers she was excited about earning a steady income to feed her young son.

Since then, she has endured long hours picking strawberries, often under an extreme California summer heat. On some occasions, she has taken home $30 a day, hardly enough to pay for the bedroom she rents for $500 in a private home.

Now, her son, a high school senior who is fluent in English and Spanish, aspires to secure employment outside agriculture—a trend among a younger generation of immigrants and U.S.-born children who have seen their parents toil in California’s billion-dollar agriculture industry while living in poverty.

“They want to prepare themselves for a better job,” says Perez.

Leaning against a four-foot fence that divides the street from the vast strawberry farm, the 39-year-old looks at her co-workers as they move across the lush terrain. Their crouched bodies come upright only to fill their strawberry cases.

Covered from head-to-toe with layers of sweaters, handkerchiefs and hats, agricultural laborers work with fumigants and pests. Perez encourages her son to study hard to get a job outside the fields.

Employers say there are just not enough farmworkers to pick the fruits and vegetables. “There’s a grower who was bringing in 40 workers to pick lemons from Arizona,” said Daniela Ramirez, coordinator with House Farm Workers! Her group works primarily to assist workers obtain adequate housing.

“Right now, the labor supply is fairly tight,” says Nick Frey, president of the Sonoma County Winegrape Commission.

“The people who are documented and have their lives here—their children grow up and go to college. Some will come back and work for us as line packers but others move on to other careers,” Frey, who himself is the son of a farmer, told the California Health Report. “That’s not too uncommon in American agriculture.”

As Congress inches toward reshaping immigration laws, few agree on what measures should be included in an overhaul. Citing a sharp labor shortage, farmers and ranchers in California—one of the largest farm states in the nation—say a short supply of field workers is hurting their businesses. They are aggressively lobbying Congress for agricultural work visas.

On the laborers’ side, immigrants like Perez and their advocates are pushing for a solution that will allow people like her to adjust their immigration status. They say that any temporary visa program leaves an already vulnerable population susceptible to exploitation.

Earlier this month, hundreds of farm workers, students, religious leaders and grassroots organizers rallied in cities across the Golden State, including Bakersfield, Fresno and Oxnard, to urge lawmakers to allow the estimated 11 million undocumented immigrants to live here lawfully.

Frey says that while agriculture employers have the H-2A visa, a type of temporary program that allows farmers to hire foreign workers when they can’t fill the jobs with U.S. employees, these visas are expensive and “are not user-friendly to operate under.”

“The H-2A program is not very robust. It doesn’t meet the demands,” he says.

Employers are poised to face years of labor shortages as an older generation retires and fewer new immigrants decide to cross the border, Frey says. Research suggests that Mexican immigrants are no longer moving to the U.S. in waves as they did starting in the 1970s.

Tighter borders, mass deportations, and a sluggish U.S. economy have deterred some from migrating here. That, combined with long-term declines in birth rates in Mexico and improving economic conditions there, has resulted in a zero-net migration in 2011, a recent Pew Hispanic Report showed.

“There’s a real concern,” Frey says. “Where are you going to find the workforce?”

Some immigrant advocates have a message for these employers: raise wages.

“In any other industry, when employers confront labor shortages, they raise their salaries and take pains to make their jobs more attractive to potential and current workers,” Farmworker Justice President Bruce Goldstein wrote in a recent opinion piece. “If they can’t compete on that basis, something is wrong with their business model.”

But the labor shortage is the result of more than just strict immigration laws, says Niam Rafferty, operations manager for the Western Farm Workers Association in Yuba City, a city about 40 miles north of Sacramento.

Increased mechanization, market downturns, the rise of agro-businesses and trade policies such as the North America Free Trade Agreement have transformed the landscape of agriculture.

To reduce the price of labor, for instance, some producers have moved jobs abroad, making it harder for U.S. farmers to compete when those products are trucked back into the country. American farmers unable to compete with Mexican-grown asparagus, which can sell more cheaply, simply stopped growing it.

Stockton’s Asparagus Festival attracts hundreds of thousands of visitors from all parts of the state each year. Yet the labor camps that once employed a bounty of asparagus pickers have been dwindling as the state’s growers have drastically reduced production.

Not long ago, five area asparagus labor camps were filled to capacity. This time around, Rafferty says, only one was open. Workers told her their earnings do not justify their traveling expenses.

Even during a labor shortage, Rafferty explains, farm workers continue to be among the lowest paid workers.

On a perfectly mild Wednesday afternoon, Perez’s supervisor, a man driving a red pickup truck who would not give his name, says he’s paying workers more money to ensure he has enough employees during the strawberry peak season.

Standing only a few feet from him, Perez is eager for the season to arrive. Since she began earning a dollar more per hour at the start of the year, she’s received fewer hours to work.

With a worried look on her face, the single mother says will be lucky if she gets to work 20 hours on this week.