It may seem paradoxical that while the number of migrants arriving in Europe has fallen by 90 percent from its 2015 peak, the refugee camp on the Greek island of Lesbos has grown into an unspeakable hell, where asylum seekers are driven to madness and suicide. Sadly, the horror of Camp Moria described by Patrick Kingsley of The Times this week is the price of the actions that have stemmed the flow of refugees.

When the flood of refugees was at its high point, Camp Moria was basically a way station, one of the first stops for asylum seekers, many fleeing war in Syria, Iraq and Afghanistan, on their way to the European mainland. But as the European Union has responded to the crisis by closing internal borders and cutting deals with Turkey and African governments and warlords to slow the exodus, many of the migrants have become stranded where they first make landfall.

Though only about 23,000 refugees have reached the Greek islands this year, down from 850,000 in 2015, they must now wait at camps like Moria for as long as two years before they are either sent back or sent on.

The squalor and dangers of the camp are unlikely to draw criticism from President Trump, whose cynical efforts to curb legal and illegal immigration were highlighted by the decision announced last month to reduce next year’s refugee resettlement quota to 30,000, the lowest ever. As recently as 2016, the United States admitted 85,000 refugees.

Mr. Trump has also shown no scruples about his inhumane policy of separating families. Struggling to find room for 13,000 detained migrant children, whose numbers have increased more than fivefold since last year, the administration has roused hundreds of children in the middle of the night and bused them to a sprawling tent city in the West Texas desert.

At Camp Moria in Greece, conditions are grim. Mr. Kingsley describes a camp built for 3,100 now overflowing with three times that many. There’s one cold shower for each 80 people, one foul toilet per 70; people stand in line all day for food and wait months for an interview; gangs prey on the weak; sexual assaults are common; and suicide attempts are constant. With no room for more refugees, the camp has overflowed into rough encampments beyond its fences. Greece has now begun moving some of the most vulnerable refugees to Athens, but that is not likely to make a big difference soon.