Today, President Donald Trump will reportedly issue an executive order to begin construction of a wall along the U.S-Mexico border. The long-awaited move follows through on one of Trump’s most visible campaign promises.

It’s also a big mistake. Not only would a wall be outrageously expensive — estimates range as high as $14 billion (and no, Mexico won’t pay for it) — but a wall is misguided because it addresses the exact wrong problem. The biggest immigration crisis facing the country has nothing to do with Mexicans illegally crossing the border. Instead, it’s that hundreds of thousands of Central Americans are fleeing brutal violence and extreme poverty in their home countries and seeking asylum in the United States — but our immigration system is overwhelmed and completely unprepared to handle the flood.

I know this issue firsthand. Over the past two decades, I have served in senior homeland security positions in both the George W. Bush and Barack Obama administrations — first as policy director for U.S. Customs and Border Protection in the years after the 9/11 attacks, and most recently as assistant secretary of homeland security for border, immigration and trade policy in the Obama administration. During those years, I have seen an extraordinary transformation not only of our border, but also in our deepening relationship with Mexico.

It’s true that in the 1990s, the border was out of control, with illegal entries approaching 2 million a year. But since then, we’ve dramatically strengthened enforcement by tripling the size of the Border Patrol, deploying drones and, yes, constructing hundreds of miles of fence along the border. It’s now hard to cross, and the economics of human smuggling show this: It now costs 12 times more in real dollars to hire a “coyote” than 15 years ago. That’s dramatic bipartisan progress in securing our border, although you wouldn’t have known it from last year’s presidential campaign.

More importantly, Mexico has changed. Over the past two decades, it has grown into the world’s 11th largest economy, deeply integrated with ours through cross-border infrastructure and supply chains, all facilitated by binational efforts to reduce barriers to commerce at the border. As a result, there are good jobs for Mexicans in Mexico — and, thus, more reasons for Mexicans to stay. This was certainly true during our economic crisis of 2008-09, but it remains true today.

In fact, according to the Pew Research Center, more Mexicans now leave the U.S. than head north, and border apprehensions are down a whopping 75 percent since 2000. Simply put, fewer people are coming, and our border authorities catch and remove most who try.

This is not to say there isn’t a crisis, however. There is one, but it’s different from the one Trump thinks exists. It doesn’t involve Mexican migrants, and a wall won’t solve it. The actual crisis involves thousands of migrants from Central America’s “Northern Triangle” — El Salvador, Guatemala and Honduras — who are fleeing brutal gang violence, extreme poverty or malnutrition. Roughly half of these migrants are women and young children escaping desperate circumstances, facing the real possibility of death or rape if they stay. Others are fleeing extreme poverty in remote regions where education ends at the sixth grade and families are limited to one meal a day.

America obviously cannot solve all the economic problems of Central America, but under U.S. and international law, all migrants are afforded the opportunity to apply for asylum protection if they make it to U.S. soil. If U.S. immigration officials make an initial determination that the migrants have a “credible fear” of harm back home, they are referred to U.S. immigration courts for a full hearing on their asylum claim. Unaccompanied children who reach the U.S. are quickly either placed in foster care or with U.S.-based relatives while their asylum claims are heard in court. Given the dangerous conditions in Central America, nearly half of these asylum claims ultimately succeed.

Far from evading authorities, most of these migrants from Central America want to be caught by the Border Patrol, so they can claim asylum. This is very different from the immigration crisis that Trump imagines, where undocumented Mexicans cross the border and go into hiding. In fact, fewer Mexicans are doing this than at any time in the past few decades. We don’t have a border security crisis or an uncontrolled flood of people coming from Mexico to take our jobs. Instead, we have a humanitarian crisis.

It’s also a crisis of our immigration system, which is now bursting at the seams from processing this influx. Currently, there is a 500,000-case backlog in the immigration courts — with many cases pending for five years or more. This backlog ripples its way through the system because we can’t send people back who have pending asylum claims and we can’t and shouldn’t detain people during that delay. So the smugglers tell migrants if they get to the border, all they need to do is make a minimally credible claim for asylum and they’ll be allowed to stay for the many years it takes to resolve it in court. The smugglers aren’t wrong.

Spending $14 billion to build a wall isn’t going to solve this problem. Under the law, migrants are entitled to have credible asylum claims heard. We can’t just bounce kids and families seeking protection off a wall, and leave them to their fate on the other side. Not only would this be immoral, it would be illegal: U.S. and international law mandate that we afford all seeking entry an ability to claim asylum if they have a credible fear of harm in their home country. Even if we were to build a wall along the border, such a wall wouldn’t block these migrants seeking asylum because many seek entry through our official ports of entry, such as Laredo or El Paso. You can’t just build a wall across Interstate 5 at the border between San Diego and Tijuana, or sever the Bridge of the Americas connecting El Paso and Juarez unless one wants to completely cut off America from Mexico, our third-largest trading partner. That is not a realistic option, so Central American asylum seekers will still come, whether there’s a wall or not.

Moreover, building a wall would jeopardize our close partnership with Mexico — which plays an indispensable role in managing the northbound migration flows by apprehending thousands at the Mexico-Guatemala border and sending home those who don’t need humanitarian protection. If we build a wall that the Mexican people view as insulting, Mexican politicians gearing up for their 2018 presidential elections may cease cooperation with the U.S., resulting in the freeing those thousands of Central Americans whom the Mexicans currently intercept at their border to come to our border. Ironically, the misguided effort to keep Mexicans out by building a wall would result in only Mexico allowing more Central Americans to come to our border.

Instead of building a useless, expensive wall, Congress should use the money more wisely, focusing on re-establishing the rule of law, while meeting our humanitarian obligations. Lawmakers could help fix the immigration system by providing more resources so the immigration courts can efficiently and fairly process asylum claims. Officials can work to really crack down on the smuggling gangs and financial facilitators who prey on vulnerable populations by deepening our law enforcement cooperation with Mexico and the Northern Triangle countries. We should work with our partners to create a safe, credible and efficient process for potential migrants to have their humanitarian claims adjudicated in their home countries or within the region. Specifically, the U.S. should work with Mexico, the Northern Triangle nations and the United Nations high commissioner for refugees to establish a robust regional refugee resettlement program that would evaluate claims in the Central American region, protect people from harm while they wait, and then resettle those needing protection in other countries, including the United States.

Most importantly, the U.S. government must continue to help Central American countries fight corruption, defeat gangs and develop their economies. Fundamentally, the only way to truly prevent people from migrating to escape harm or find a better life is to give them a reason to stay home.

These are all real measures that could actually address the real problem. A wall is not one of them.

Seth M.M. Stodder served in the Obama administration as assistant secretary of homeland security for border, immigration and trade policy. He previously served in the Bush administration as director of policy for U.S. Customs and Border Protection.

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