Michael Dear is emeritus professor in the College of Environmental Design at the University of California, Berkeley, and author most recently of Why Walls Won’t Work: Repairing the US- Mexico Divide (2015, Oxford University Press).

“Oh, we’re going to build a wall, don’t worry about it,” President Donald Trump told the crowd gathered to hear him at the Conservative Political Action Conference on Friday. “In fact, it’s going to start soon. Way ahead of schedule. Way ahead of schedule. Way, way, way ahead of schedule. It’s going to start very soon.”

So much for my hopes that Trump might have abandoned his campaign pledge to build a “big, beautiful” wall on the Southern border. The president seems convinced that a 1,300-mile contraption will solve America’s immigration woes. According to the executive order the president signed in late January, the wall is supposed “to prevent illegal immigration, drug and human trafficking, and acts of terrorism.”


But the reality is that a wall, no matter how “big,” how “beautiful,” and how “ahead of schedule” Trump builds it, cannot be an effective enforcement tool. The immigration system is plagued with problems and factors that building a wall cannot fix. It might just end up making some of them worse.

Here are five problems the wall can’t solve.

1. A lot of undocumented immigrants are already here.

The president implies that a border wall will keep out droves of undocumented immigrants each year. But new Department of Homeland Security (DHS) data reveals that a main source of illegal immigration into the United States are people who arrive legally then overstay their visas. DHS estimates that of the 45 million immigrants who entered the U.S. by air or by sea on tourist or business visas that expired in 2015, roughly 416,500 were still living in the country in 2016. That’s excluding those who entered via land boundaries—DHS did not release that data—so, the total number of visa overstays in 2016 is likely much higher. (By comparison, between 2011 and 2016, total apprehensions at the southern border ranged from 328,000 to 479,000 per year.)

There have been moves to fix the problem. Since 1996, Congress has passed seven laws mandating biometric entry-exit screening for foreign nationals, which would help track visa overstays. But due to a number of factors, both technical and financial, the system has never been enacted. Maybe Trump will have more luck. Another executive order, dated January 27, requires DHS to “expedite the completion and implementation of a biometric entry-exit tracking system for all travelers to the United States.” Regardless, a new wall isn’t going to do anything to help.

2. Cartels can outsmart checkpoints.

Trump seems to think that a wall can stop the flow of drugs and guns across the border. But if anything, the 650 miles of wall that already exist have made it easier on Mexican cartels to organize and control the transportation of illicit goods.

There are only a dozen-or-so official “ports of entry” along the border line. They are highly regulated and policed, but cartels much prefer to exploit their predictability and rationality than to scatter resources across open expanses of desert and river. Traffickers have carefully studied how security operates in each checkpoint, which means they can observe and instantly respond to weaknesses, such as when inspections are relaxed in order to speed up the through-flow of traffic, or when a corrupt inspection officer with a willing blind eye comes on duty.

Cartels are clever and tactical in adjusting their behavior. Lately, they have begun smuggling weapon parts into Mexico rather than whole guns, because parts are easier to conceal and have no identification numbers, making them harder to trace.

Of course, it’s likely that not all shipments will get through the checkpoints on any given day, but such losses are factored into cartel calculations, and it’s still better than risking people and product in an unpredictable wilderness.

3. Terrorists aren’t undocumented.

Trump has proclaimed that building a wall on the Southern border will thwart terrorists. Yet there is no evidence that any terrorists have ever entered the U.S. through the Mexican land boundary, and the Department of Homeland Security has long held that it has “no credible intelligence to suggest terrorist organizations are actively plotting to cross the southwest border.”

In fact, most terrorists active in the United States are homegrown. Since 9/11, over 80 percent of individuals who were charged with or died while engaging in jihad-related terrorist activities in this country have been U.S. citizens or permanent residents.

As for those terrorists who are foreign born, according to a list complied by Alex Nowrasteh, of 154 foreign-born people who committed or plotted terrorist attacks on U.S. soil from 1975 through 2015, only 1 was Mexican.

4. It’s the economy, stupid.

The main reason people risk undocumented migration is to find work. The Mexican recession of the 1980s brought waves of undocumented immigrants into the U.S. looking for employment, but their numbers declined dramatically as Mexico’s domestic economy strengthened. These days most Mexicans moving to the border intend to stay in Mexico and work in the booming local manufacturing, health care and education industries there; they have no intention of crossing into the U.S.

But the Mexican economy is now showing signs of stress. Border communities suffered much disruption since the first walls started appearing in 2006, including the environmental damage caused by its construction and the increased costs of doing business due to prolonged crossing times. Trump’s new wall is likely to make things even worse. Couple that with his tough talk about renegotiating NAFTA or launching a trade war against Mexico, and the possibility of a borderland recession and massive unemployment only goes up. A surge in undocumented immigration will be sure to follow.

5. Immigration courts are already overwhelmed.

Collateral damage caused by our broken immigration system is most clearly evident in the U.S. immigration courts, which for years have been clogged by ever-increasing deportation caseloads.

During the administration of President George W. Bush, the annual rate of federal criminal prosecutions for immigration offenses more than quadrupled. Starved of resources and plagued by too few judges, the courts conducted proceedings involving as many as 80 migrant cases at a single time, in clear violation of federal law. Not to mention the flood of deportations diverted U.S. attorney offices away from prosecuting more serious cases against international crime and drug cartels.

Under President Barack Obama, deportations continued to rise, reaching record highs of over 400,000 annually. During his second term, Obama increased the number of judges adjudicating these cases and shifted attention away from minor offenders, but the problem of crushing caseloads persists. In 2016, the backlog of cases reached 474,000, climbing to 533,000 in 2017. Wait time for a court hearing averages three years.

Our immigration courts are already poised at breaking point, but Trump announced his intention to target 3 million more people for deportation. If this happens, the immigration court system will simply grind to a halt.