On Wednesday evening, fresh off a conciliatory meeting with Mexican President Enrique Peña Nieto, Republican presidential nominee Donald Trump took his theory that immigrants are the major source of America's ills to a new extreme.

"All energies of the federal government and the legislative process must now be focused on immigration security," Trump said. "Whether it's dangerous materials being smuggled across the border, terrorists entering on visas, or Americans losing their jobs to foreign workers, these are the problems we must now focus on fixing."

Trump's prescriptions for fixing those problems, however, would have a profoundly negative impact on the American economy - and Texas, in particular - where immigrants, here illegally and otherwise, build new homes, pick crops, clean hotel rooms, landscape suburban properties and spend their earnings to support a wide variety of businesses. Texas hosted 1.7 million unauthorized immigrants - about 80 percent of whom are from Mexico - or nearly 9 percent of the labor force in 2012, according to the Pew Research Center, a nonprofit, nonpartisan public policy group.

Although Trump downplayed his previously outlined plan to immediately deport all those living in the United States illegally, he reiterated that none would be able to gain legal status without first leaving the country, and none would be able to work without legal status.

If enforcement went as planned, that would decimate the workforces of industries such construction, agriculture, hospitality and landscaping.

"It would have a devastating impact on the economy," says Charles Foster, an immigration attorney who also heads the Greater Houston Partnership's immigration task force and has advised several presidents on immigration policy, including George W. Bush and Barack Obama. "We have unemployment in Houston in the oilfield sector, but that doesn't mean those workers are going to go do a job in a restaurant. It would create a recession much, much bigger than the last recession of 2008 and 2009."

Employers, naturally, deny they have unauthorized immigrants working for them - that would be a crime. But workers have proven adept at obtaining forged documents, allowing businesses to at least look the other way. And some business people will speak in broad terms about what could result from Trump's proposals.

"It would be to our detriment as a state if they had a mass exodus of people that did not have legal status to work here," said Julie Parish, president of a Houston cleaning service called Home Keepers.

That's not just because of jobs that would go unfilled. It's also the housing that would go unoccupied, the cars that wouldn't be purchased, and the families that would be left unsupported if parents were sent out of the country.

Growth slowed in Arizona

In Arizona, after the state adopted a law cracking down on illegal immigration, the population of undocumented workers plunged by 40 percent and economic growth slowed significantly - 2 percent a year between 2007 and 2012, according to an analysis by Moody's Analytics for the Wall Street Journal.

It's true, as Donald Trump points out, undocumented immigrants come with some costs. They bear children, who go to state-run schools; they have health problems, and go to municipal hospitals; and they sometimes commit crimes, which requires local jails.

But immigrants in the county illegally are ineligible for most government benefits, like cash welfare and unemployment insurance. And while much of their income might be off the books, they still pay their share of sales and property taxes. The last time Texas took stock of the equation in 2006, the state comptroller found that illegal immigration created a net benefit to the state of $425.7 million a year.

Trump argued that deporting undocumented immigrants would free up jobs for Americans - "in particular," he argued, "African-American and Latino workers who are being shut out in this process so unfairly."

But Horace Brown, chair of the labor and industry committee of the Texas chapter of the NAACP, rejected that assertion, noting that minorities face far greater barriers to employment, such as racial discrimination, poverty, and inadequate public schools, than competition with immigrants in the country illegally.

"I don't see that deporting the immigrants would do anything to help African-Americans gain employment," he said. "What would help that is businesses creating jobs, and looking to hire minorities, whether they're immigrants or whomever."

In low-skilled fields, where the presence of undocumented immigrants is strongest, economists say it would usually not be possible for employers to offer a wage high enough to attract American workers (as Trump himself has argued, in defending his requests for foreign worker visas for his hotels in Florida). If they did, said Madeline Zavodny, an economics professor at Agnes Scott College in Atlanta, it would send some of the low costs for goods and services that Americans take for granted skyrocketing.

"Would I pay $20 for a tomato?" said Zavodny, who has studied immigration in Texas. "There's a wage people would work for. The problem is that it wouldn't be slightly higher."

Decline in immigrants

Lately, due in part to an aggressive deportation campaign mounted by the Obama administration, it seems there may not even be enough immigrants to fill jobs that Texas has available. The Mexican-born population in the United States peaked in 2007 and has fallen slowly since, according to Pew. In fact, the number of people moving back to Mexico exceeds those coming in - suggesting that Trump's proposal for a "an impenetrable, physical, tall, powerful, beautiful southern border wall" wouldn't have much of an impact anyway.

That decline has left Texas' agricultural industry, in particular, complaining of a shortage of workers for labor-intensive products such as fruits and milk. "The farm labor situation in America is in crisis right now, and it's getting worse," said Gene Hall, a spokesman for the Texas Farm Bureau, which advocates for an expanded guest worker program that would allow businesses to hire foreigners temporarily. "Just sending all of the people home, without having them be able to come back and work, would be problematic."

The Farm Bureau is silent on what to do with the undocumented workers already here. But many economists, including those at the Dallas Federal Reserve Board, suggest that the best solution might be to grant them legal work status. Since undocumented immigrants can't speak up against labor violations for fear of deportation, and are usually paid in cash, it drives down wages for other workers, and deprives the state of tax revenues.

That's been frustrating to business people like Stan Marek, the chief executive of a construction company and a vocal supporter of legalization. As someone committed to above-board business practices, he could get outbid by a contractor who instead pays unauthorized immigrants under the table and fires them if they complain.

"If you have one contractor in one market who treats their workers as a disposable tool, everyone has to compete with them," Marek said.

It's true, allowing immigrants in the county illegally to bargain for better wages would raise labor costs. But not as much as kicking all of them out.