THE 16-year-old Gambian who was discovered by a Spanish naval ship as he clung to a fuel tank in open seas will doubtless be haunted by his experience for the rest of his days. But he was also exceptionally fortunate—the only survivor, by his account, among more than 140 people who left the Libyan port of Sabratha on a large rubber dinghy on March 26th or 27th. It began taking on water a few hours later, he told UN officials from his hospital bed on the Italian island of Lampedusa.

Details of sinkings in the central Mediterranean are often sketchy and sometimes unconfirmed. The Libyan Red Crescent said no bodies had been found from the disaster the young Gambian reported. But it is clear from figures kept by international organisations that both the risks of setting out from Libya and the numbers reaching Europe are growing.

According to the International Organisation for Migration, 24,513 people had landed in Italy this year by April 2nd. That was an increase of about 30% compared with the first three months of last year. Yet UNHCR, the UN refugee agency, calculates that the death rate per 100 arrivals climbed from 1.8 in 2015 to 3.4 in the first three months of 2017. One in 30 migrants in the central Mediterranean now dies en route.

Carlotta Sami, UNHCR’s spokeswoman in Italy, lists several reasons why. The smugglers are not just sending the migrants to sea in dinghies, or rigid inflatable boats (RIBs), which were never intended for long-distance sea voyages, but in RIBs of progressively poorer quality. They are increasingly reluctant to supply their customers with satellite telephones to make contact with rescue services and report their positions. And, since last summer, they have taken to dispatching several vessels at a time. That makes it harder for NGOs and the ships of Operation Sophia, a European naval force operating off the Libyan coast, to rescue them all.

Plans have been proposed to block the traffickers’ routes, which might deter migrants from assuming the appalling risks. The EU is training about 90 members of the Libyan coastguard, and Italy will soon return ten of the Libyans’ boats that were seized in 2011. Blocking the dinghies would stop not only economic migrants but also asylum-seekers fleeing war and persecution. It is hard to tell the two groups apart, but more than 40% of applicants for asylum in Italy are judged to deserve some form of humanitarian protection.

The task is complicated by Libya’s messy civil war. The UN, America and Italy have sponsored a Tripoli-based Government of National Accord (GNA). But its authority is challenged by Khalifa Haftar, the commander of a self-styled Libyan National Army (LNA). He enjoys the backing of a rival administration in the east, and—more important—that of Moscow.

On April 2nd the Italian government announced a parallel effort to interrupt the flow of migrants, enlisting the help of dozens of rival desert tribes to secure Libya’s southern frontier, which is 5,000km (3,100 miles) long. The Saharan borders have until now been a playground for smugglers of drugs, arms and people. The interior ministry said 60 tribal leaders had signed up to a 12-point deal, hammered out in several days of secret talks in Rome.

Few details have been released of the agreement, which reportedly pledges investment in the area to create legitimate jobs for young people, and opens the way for “unified patrolling of the borders with Algeria, Niger and Chad”. Yet it remains uncertain who will do the patrolling. Nor is it clear how much common purpose can be found among the tribes. The Toubou peoples on Libya’s border with Chad, for example, have a history of conflict with neighbouring Arab tribes which are also supposedly backing the deal. But the area is crucial to reducing the number of migrants travelling across the Sahara. That voyage is every bit as risky as the one migrants are making across the Mediterranean. As the numbers make clear, the risk of death is not enough to stop them.