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.
There are between 6 million and 8 million people displaced in Syria, along with more than four million Syrian refugees in Lebanon, Turkey and Jordan.
Egypt's 5 million or more Copts, the Middle East's last remaining major Christian sect, are deeply worried about their future in an unstable and hostile country. Ancient minority groups like the Yazidis of Iraq are already homeless, as are many small communities of Assyrian, Nestorian and Chaldean Christians from northern Iraq.
While Yemenis have yet to abandon their homeland in substantial numbers, their plight is worsening daily amid wartime shortages of food and medicine and persistent bombardment by Saudi warplanes. Yemen is not much farther away from Europe than Eritrea, now the biggest source of African refugees, just across the Red Sea, and at some 25 million it is as populous as Afghanistan.
Biggest influx in modern history
Nor is it only the Middle East and North Africa that European leaders need to consider. The Gallup Poll, based on data compiled from more than 450,000 interviews in 151 nations from 2009 to 2011, found that in Nigeria, which already has double the population of Germany, 40 percent of people would emigrate to the West if they could. And the lesson of 2015 - for them and much of the world - is that they can.
While the flow of migrants to Europe this year already represents the biggest influx from outside the Continent in modern history, many experts warn that the mass movement may continue and even increase - possibly for years to come. "We are talking about millions of potential refugees trying to reach Europe, not thousands," Donald Tusk, the president of the European Council, said in a recent Twitter posting.
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.Climate change, too, is roiling societies across the Middle East and Africa. Syria was in the grip of a prolonged drought when war broke out, and large areas of sub-Saharan Africa are becoming uninhabitable. With rising sea levels, a single typhoon in the Bay of Bengal could drive millions of Bangladeshis from their homes in low-lying coastal areas and render that land uninhabitable, too.
Europe has spawned mass movements of refugees in the not-too-distant past - 700,000 from the breakup of Yugoslavia in 1993, 1.1 million from Eastern Europe as the Iron Curtain was torn down in 1989 - but what is new now is not just the scale of the arrivals, in such large numbers over such a short period of time. It is also the sheer number and variety of problem places they are leaving behind.
Intervened and failed
Many migrants are from countries where the West has tried to intervene and failed spectacularly - Iraq and Afghanistan, in particular.
There are now some 2 million Iraqi refugees, many bound for Europe. Among them are people like Muhammad Basher, a young Kurdish doctor from Iraq, who took his life savings of $2,000 and had spent nearly all of it by the time he reached the Croatian border - $1,200 just for a seat in a rubber dinghy on a dangerous sea crossing to Greece.
"Better to die quickly there, than slowly in Iraq," he said.
Sayid Karim Hashimi, 23, a native of Kunduz, was among the Afghans recently crossing the border out of Serbia."There is no future in Afghanistan," he said.
Libya represents another failed intervention, by the French and British, with American support. Although few Libyans have been prompted to join the exodus, the chaos in their country has made it easier than ever before for other African migrants to flee to Europe through northern Africa.While most of the migrants have been from Syria, Iraq and Afghanistan, those who came through villages like this last summer could have arrived from almost anywhere.
Two women from Haiti and a young girl, the daughter of one of them, passed through in early October, according to officials here representing the U.N. High Commissioner for Refugees. They had flown to Turkey from Haiti, then joined smugglers' routes through the Balkans.
Others come from places like Eritrea, where young men are fleeing a brutal dictatorship that offers them the prospect of a lifetime of unpaid military service, and little else. Some are escaping civil war in the Democratic Republic of Congo or poverty in nations like Gambia or Senegal. Many, especially in sub-Saharan Africa, are motivated by elemental problems like spreading desertification. Others are looking for economic opportunity.
Ibrahim Isahaq, 18, from Ghana, was among those migrants who came through Serbia in October, attracted by news of how easy passage had become. He was simply fleeing a family feud over a disputed inheritance. Youssou, 25, from Senegal, said his father was a commander in the little-known Casamance separatist movement, but he seemed more interested in business prospects in Europe.
"There was no life for me in Senegal," he said.
While the migrant crisis has inspired a backlash among Europe's right-wing nationalist parties, particularly in the East, authorities say the problem is still manageable.
"We need to keep our perspective on the numbers," said Alexander Betts, who heads the Refugee Studies Center at Oxford University. "If Lebanon can host 1 million Syrians, despite being the size of Maryland, a region the size of Europe should be able to host millions."
Even in the four European Union member countries that initially opposed a modest 120,000-migrant per nation resettlement quota - Poland, Slovakia, the Czech Republic and Hungary - voices were raised in support of the migrants, who were to be distributed across the 28-member bloc. Though a quota system has yet to take full effect, a recent appeal, signed by former presidents and prime ministers and other prominent Europeans, many from those four countries, called on their countries to abandon their hostility to the migrants and remember their own recent past.
That might be a hard sell, however, in a Europe already preoccupied with terrorist recruitment among disaffected Muslim populations from earlier, much smaller migrations.
"Throughout Europe, xenophobia and open racism are running rampant, and nationalist, even far-right parties are gaining ground," Joschka Fischer, the former German foreign minister, wrote recently in an article that appeared on Project Syndicate, an online news service.
"At the same time, this is only the beginning of the crisis, because the conditions inciting people to flee their homelands will only worsen. And the EU, many of whose members have the world's largest and best-equipped welfare systems, appears to be overwhelmed by it - politically, morally and administratively."
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."