Refugees and migrants sit next to tents at the Souda municipality run camp on the Greek island of Chios on September 7. (Alkis Konstantinidis/Reuters)

In the midst of the greatest migration upheaval since the end of World War II, world leaders will gather Monday in New York for a major U.N. summit on the global refugee crisis.

While the summit’s main agenda item will be the 22-page proposal drafted to strengthen protections for migrants — by ensuring “a people-centered, sensitive, humane, dignified, gender-responsive and prompt reception” — the situation in the Mediterranean Sea, the transit zone where more than a million people passed into Europe last year, is anything but safe.

After the landmark agreement between the European Union and Turkey signed in March, the traffic along the eastern Mediterranean route — from the Middle East through the Aegean Sea, used by most of the migrants and refugees who arrived last year — has generally slowed, although the United Nations’ refugee agency reported an uptick in the first week of September, with more than 1,000 migrants crossing into Greece from Turkey.

Meanwhile, traffic along the less-regulated central Mediterranean route, typically with migrants from North Africa and sub-Saharan Africa headed to Italy and its outer islands, has increased after a long summer of warmer weather and improved travel conditions. Although the overall flow of migrants across the Mediterranean has fallen this year, the number of deaths at sea has risen by about 15 percent, according to the most recent statistics collected by the International Organization for Migration.

Through the end of September 2015, the organization reported that 470,000 migrants and refugees had arrived in Europe and that an additional 2,900 had died while attempting the journey. By comparison, through Sept. 14 of this year, the IOM reported that 297,000 have arrived on the continent, while 3,200 have died en route.

“We already know the U.N. summit is doomed to abject failure,” Salil Shetty, Amnesty International’s secretary general, said in a statement in advance of Monday’s assembly. “Faced with the worst refugee crisis in 70 years, world leaders have shown a shocking disregard for the human rights of people who have been forced to leave their homes due to conflict or persecution.”

In geopolitical terms, analysts say that a continued flow along the eastern Mediterranean route, even a small one, risks upsetting the E.U.’s deal with Turkey, especially given tense relations after the attempted coup against the Turkish government in mid-July.

In August, approximately 3,400 migrants arrived in Greece by sea, the highest number since April, the month that immediately followed the signing of the deal. The reason for this increase remains unknown.

According to Elizabeth Collett, director of the Brussels-based Migration Policy Institute Europe, it is not the numbers that present an issue. Rather, the potential problem lies in the pressure the constant influx will place on Greece, where, she said, detention centers are overcrowded, few adequate facilities have been prepared, and migrants are “underserved by overstretched services.”

These difficult conditions could force Greek authorities to transport migrants from outer Aegean islands to the mainland. But according to the E.U. agreement with Turkey, that country will take back migrants only from the outer islands, not from mainland Greece.

“There’s this children’s game called Jenga,” Gerald Knaus, a member of the European Council on Foreign Relations and a founding member of the Berlin-based European Stability Initiative, said in an interview. “If you pull out the wrong block, the whole thing might come crashing down.”

“The paradigm in Europe has been making sure the Turks don’t walk away from the deal,” he said, “but that’s not the danger. The danger is that nobody does anything. It’s not the numbers themselves that are the problem, it’s the potential for mistakes they create.”