IT IS a grand European project, born of integrationist ideals yet undermined by participants’ unwillingness to share costs as well as benefits. No, not the euro zone, but the Schengen agreement between 26 European countries to eliminate controls at their common borders. Europeans benefit enormously from their ability to move freely between countries. But the waves of migrants looking to enter the continent impose a burden on its southernmost countries that must be shared more evenly. If not, Schengen itself could unravel.

Whether they seek shelter from persecution or economic opportunity, illegal migrants are keenest to reach Europe’s richer, northern countries. Many migrants head directly to these countries, often by air, arriving on a legal visa and staying on when it expires. But geography and the economics of migration mean that the most desperate travel by sea and land from Africa and the Middle East. And their first contact with western Europe is on the continent’s periphery—Mediterranean islands like Lampedusa and Malta for the dangerously overcrowded boats from Africa, Greece’s eastern frontier with Turkey for those trekking from Syria and beyond.

The risks these travellers take are immense. According to a recent report by Amnesty International, a lobby group, at least 23,000 migrants have lost their lives trying to reach Europe since 2000. And the numbers are rising fast, thanks to the conflicts that rage in Syria, Iraq, Libya and elsewhere. This is shaping up to be the worst year in decades for the number of illegal arrivals at Europe’s outposts (see article). From January to July alone around 100,000 undocumented migrants crossed the Mediterranean into Italy, already much more than the record 60,000 who made the crossing in all of 2011. In the same period, the number of illegal migrants arrested by the Greek authorities at the border with Turkey rose by 143%.

That puts a big strain on the countries on the geographical front line. Italy spends €9m ($12m) a month on Operation Mare Nostrum, a laudable search-and-rescue effort in the Mediterranean, which was launched in October 2013 in response to the drowning of 360 migrants off Lampedusa. Italian patrol boats picked up around 5,000 people on a single weekend in June; Spanish ones over 1,200 in two days earlier this week. Malta has more asylum-seekers per person than any other rich-world country.

A problem shared

Northern Europeans’ response is to shrug. Italy’s requests for assistance with Mare Nostrum have got nowhere. Greece spent €63m in 2013 to prevent illegal immigration; just €3m came from Europe’s border agencies. The Schengen agreement enshrines the responsibility of the littoral states. The Dublin regulation, a building block of Schengen, says that the first EU state where a migrant arrives, his finger prints are stored or an asylum claim is made is responsible for the asylum claim. If a migrant is processed in Greece, then he is Greece’s problem.

That is unfair and short-sighted. Unfair, because migrants themselves see a place like Greece as a way station, not a final destination. The allure of Europe for illegal migrants rests primarily in rich countries; the burden of catching and dealing with them should not lie with countries simply because they happen to be en route. It is also short-sighted, because it creates perverse incentives for border countries to soften their border controls: better not to fingerprint migrants and let them go to the richer northern countries than to put them on record. In 2013, for example, German officials accused Italians of slipping refugees money so they could travel to Germany. Such episodes foster suspicion, and thus threaten to destroy a system based on trust between member states.

The answer is to require European states to share the burden of illegal migration more equitably. Cecilia Malmstrom, a Swedish politician who is the EU commissioner for home affairs, has mooted the idea of a “distribution key” whereby member states who have few asylum-seekers—Poland, for example—take more of them. Another option would be to distribute migrants among states in proportion to population. That will not go down well with many Schengen countries. But the logic of the free movement of people is that the more open the borders internally, the more tightly external frontiers must be managed. That burden must be shared, not shirked.