At the beginning of 2015, a united Europe prided itself on the continental freedom of travel citizens of the Schengen Area enjoyed. By year’s end, terrorist attacks and asylum seekers had fractured the borderless treaty into chaos. Like toppling dominoes one after another, European nations have reasserted their sovereignty, effectively declaring a loss of confidence in the European Union’s political integrity. If permanent border controls are introduced and the Schengen Area is dissolved, a cascading series of political, economic, and cultural impacts will be felt throughout the region and the world.

Although the path that has brought Europe to the brink of Schengen’s dissolution is well known, four pivotal events drove the border crisis. In January 2015, the Charlie Hebdo terrorist attack in Paris heightened suspicion against incoming migrants, increasing French skepticism of northern Europe’s open border policy. In August, intervention from American military personnel on leave narrowly averted an attempted terror attack on a high speed train traveling through the Netherlands, Belgium, and France, again raising questions about border screening and freedom of movement. Weeks later, border controls were imposed in much of central Europe—significantly, Austria and Germany—following a dramatic increase of migrants from North Africa, the Middle East, and Central Asia seeking refuge in Europe. Finally, the November terror attacks in Paris left an indelible, and possibly permanent, mark on French border policy.

Ten years ago, Europeans commonly scoffed at American border controls, mocking the Department of Homeland Security as ineffective at best and draconian at worst. Yet, Europe’s emerging security regime appears poised to have a much deeper and more enduring influence on a society that had previously upheld its border removal policies as the gold standard for human rights. Discussions have emerged of a “mini-Schengen” in northern Europe, effectively ending the physical unity of the European Union by cutting Italy, Greece, and the Iberian Peninsula out of the border-free travel zone. The addition of border controls, in whatever form they take, will affect an entire generation of economic agreements, trade routes, and supply chains long considered stable, not to mention young men and women accustomed to seeing themselves as liberal, cosmopolitan Europeans more than citizens of any individual nation.

What Border Crossings Feel Like

Last year, in both the spring and winter, I crossed several northern and southern European borders to gain a comparative understanding of how Europe’s increasing border controls were impacting the day-to-day routine in areas accustomed to borderless travel. In March and April, I crossed borders between Germany, the Netherlands, Denmark, Sweden, Estonia, Latvia, and Lithuania. All seven northern European countries are within the Schengen zone, and I did not encounter a single passport control or inspection checkpoint when navigating between them. The major security screening area for personnel was not between northern European countries, but at Frankfurt Airport when transiting to and from the United States. Once I passed the airport checkpoints, I was free to move with relative ease.

Southern Europe has long been a different story. Because the land route north from Greece to Hungary and Slovenia includes several countries that have always maintained border controls, crossing an inspection point and receiving a passport stamp when traveling through the former Yugoslavia had been a normal event in 2015 prior to the terrorist attacks and refugees. But along the Balkan route, the intensity of inspections—and their subsequent impact on trade and travel—has increased over the past year, which has resulted in cascading impacts on movement north from southern Europe.

In December, I traveled from Turkey to Serbia, passing through six inspection checkpoints when crossing three international borders, as well as the checkpoint at Istanbul’s Ataturk International Airport. This included an exit and entry control in each country transited, the strictest of which was Greece. Once a cursory formality, the Greece-Macedonia border inspection has become one of the harshest checkpoints I have observed in nearly a decade of border travels.

Arriving at the international checkpoint on a frigid early morning, all passengers disembarked, collected their bags, and lined up for inspection. From the border crossing from Turkey into Greece, until the Macedonia checkpoint, the bus driver retained control of every passenger’s passport—presumably an anti-smuggling measure required by EU and/or Greek authorities. The bus drivers handed the passports to Greek, and then Macedonian, authorities for two separate inspections. For 35 minutes, six Macedonian customs officers opened every compartment, shone their flashlights around, tapped on metal looking for contraband, and combed through the undercarriage. Adjacent to the bus, freight trucks were lined up over two miles awaiting clearance. We did not receive passports back until after entering Macedonia, and had not possessed them the entire time we were in Greece.

Comparing and Contrasting Borders

Two comparisons between the land border crossings in Europe and those entering the United States struck me. First, crossing a land border between most European countries requires two document and inspection screenings—one upon exiting one country; the other upon entrance into another—instead of a single point where entry and exit controls are next to each other, as is the case along U.S. land border entry points. Between the borders of neighboring nations, countries delineate up to a kilometer of empty space. For legal transients, this zone offers a duty-free store with cheap alcohol and cigarettes. For migrants illegally crossing, the dead space is a no-man’s land, providing a formidable challenge to smugglers, and enabling border enforcers time and distance to catch and apprehend any who attempt crossings beyond the checkpoint.

Second, unlike most land border interactions in Europe, the United States border does not actually start at the physical border. Well before entering the United States, passengers are screened for entry permission airports (such as Frankfurt and Istanbul) or for preclearance in Canada and Mexico at bus stations or cruise ship terminals. For companies that agree to various data exchanges with the U.S. government, cargo containers are inspected and sealed by agents authorized to act on the government’s behalf at Mexican factories or Chinese seaports. Since the volume of people and cargo entering the U.S. is too heavy to thoroughly inspect at entry points the U.S. policy has been (and continues to be) identifying which cargo and people are “trusted” with low-level screening, and what or who represents higher risk.

This policy of risk segmentation was reinforced following 9/11, when U.S. land, sea, and air ports of entry were ordered, for the first time in history, to Alert Level One, which required inspectors to physically screen all people and goods at entry points. By the next morning, traffic entering Detroit from Canada was backed up over 12 hours and trucks waited 24 hours to cross from Tijuana into San Diego. Executives from U.S. auto plants that relied on just-in-time deliveries frantically warned senior White House executives that if the wait times continued, they would be bankrupt within a week.

It’s the Economy, Stupid

In Europe, the level of unpredictability that now exists at international border crossings has left what were, for two decades, orderly processes in turmoil. Over one-third of all road freight cargo transported throughout the Schengen Area crosses an international border. Today, from Estonia to Spain, farmers, manufacturers, and retailers once accustomed to just-in-time deliveries are now adjusting to the whims of authorities at random checkpoints, creating delays ranging from hours to days. In 2015, commuting from Mälmo, Sweden, to Copenhagen, Denmark, was so routine that many Danes had moved to Sweden because of the lower property costs. Today, the new international border crossing has added hours to daily commutes, and raised questions about labor and workforce sustainability that are mirrored throughout Europe.

Over the next decade, if Schengen disappears, EU authorities estimate economic output would be reduced by $124 billion as a result of border control costs. This figure does not account for the costs that each of the Schengen Area’s 26 governments will incur for constructing, staffing, and maintaining border controls, or for the costs associated with detention and deportation programs. In the United States, the 2015 enforcement cost of border controls and immigration enforcement were $18.9 billion. In much of central Europe, countries have used emergency legal authority and ordered military forces to manage borders. Such policies would be unsustainable if Schengen fully dissolved.

Greece, Germany, and the Space Between

Although the economic impact will be felt throughout Europe as border controls tighten, the country that will suffer the most from the EU’s failure to produce a common policy to equitably manage refugees traveling north is Greece. While the country is technically still part of Europe’s travel-free Schengen Area, in practice it has been cordoned off by its own geography. Ferries to Italy are heavily screened, and Italy itself has been subjected to random passport controls for vehicles and passengers bound for Slovenia, Austria, Switzerland, and France. The Balkan countries north of Greece, as I witnessed, have turned what were once minor procedures into aggressive, time-consuming inspections.

The border control surge means Greece is particularly isolated, both physically and economically, from the rest of Europe. Unless meeting strict conditions, many arriving on Greece’s shores are not legally permitted to leave, and deportees from northern Europe whose asylum claims are rejected are returned to the country of registered arrival, most often Greece, Italy, or Spain. The entire country, and not only Lesbos Island, where millions of migrants arrived in 2015 after a three mile boat ride from Turkey, has effectively become Europe’s refugee camp.

The path from Greece into Germany that migrants take may appear anarchic, but legal migration through European land borders is unlike the increased migration that has occurred into the United States during the past two decades. Although smuggling migrants into Germany is by no means impossible, most asylum seekers who entered Germany this past year have done so with legal European Union documentation, and using a legal route. Aid workers at camps in Macedonia, Serbia, Croatia, and Slovenia process refugees through documentation checks before hustling them onto buses or trains that speed them north to the next international border crossing. The journey from a series of refugee camps on Lesbos Island to Munich might be exhausting, but most transients are neither illegal nor undocumented.

Although that may change in 2016, for all the bluster in Europe about terrorism and social change, the concentric circles of security resulting from multiple controls mean northern Europe’s borders are already tighter than those of the United States—as are the associated enforcement costs. Smugglers face, at most, three checkpoints from Mexico into the United States: an interior checkpoint in Mexico, the international border crossing, and an interior checkpoint in the United States. In Europe, a potential smuggler will hit at a minimum of twelve checkpoints driving from Athens to Munich—and this figure only accounts for exit and entry at international borders. At the end of 2015, the benefits for Syrians, Iraqis, and Afghans—the only nationalities Macedonia authorizes entry from Greece—to legally go to Germany outweighed the risks of hiring a smuggler (on February 19, 2016, Macedonia removed Afghan nationals from transit permission, leaving only Syrians and Iraqis as authorized asylum seekers).

As border controls continue tightening, and with little hope for peace in Syria, Iraq, or Afghanistan, legal and illegal migration into Europe from the Middle East will likely increase this coming spring and summer. As has happened previously in European history, and throughout the world, these new borderlands will again become places of cultural duality: regions of linguistic, ethnic, and religious fusion marked by fences, barbed wire, and signs warning the wrong people to keep out. Hardening any international border invariably generates consequences that extend beyond the two countries establishing checkpoints or building walls. This transformation of Europe will alter economic, cultural, and geopolitical landscapes, and fuel uncertainty, recession, and discord for a generation to come on the continent.