There are more displaced people and refugees now than at any other time in recorded history — 60 million in all — and they are on the march in numbers not seen since World War II. They are coming not just from Syria, but from an array of countries and regions, including Afghanistan, Iraq, Gaza, even Haiti, as well as any of a dozen or so nations in sub-Saharan and North Africa. They are unofficial ambassadors of failed states, unending wars, intractable conflicts.

The most striking thing about the current migration crisis, however, is how much bigger it could still get. What if Islamic State militants are not beaten back but continue to extend their brutal writ across Iraq and Syria? What if the Taliban continue to increase their territorial gains in Afghanistan, prompting even more people to flee? A quarter of Afghans told a Gallup Poll that they want to leave, and more than 100,000 are expected to try to flee to Europe this year.

Many of the migrants are fleeing persecution, poverty, ethnic and religious strife and war, but these afflictions are often symptoms of more profound changes. In the Middle East and Africa, borders drawn by Ottoman dynasts and European colonialists are breaking down as the autocratic Arab states that enforced a grim peace for generations continue to implode. As traditional lines of authority break down, militant groups like the Islamic State and Boko Haram, in Nigeria, seek to fill the vacuum while minority sects and ethnic groups suffer unspeakable treatment at their hands.

Those stresses pose a challenge for the future, experts say, because the flow is unlikely to ebb anytime soon. “I don’t think this wave can stop,” said Sonja Licht of the International Center for Democratic Transition. “It can maybe from time to time be somewhat less intensive, we simply have to prepare. The global north must be prepared that the global south is on the move, the entire global south. This is not just a problem for Europe but for the whole world.”