Jack Nicas and Maria Magdalena Arrellaga

The Aquidaban has long attracted colorful characters as the only ferry in one of South America’s most remote stretches. Now it may disappear.

In Paraguay, the Colorado Party has held power for seven decades. On Election Day, it rounds up Indigenous people and pays them for their votes.

The Landless Workers Movement organizes Brazil’s poor to take land from the rich. It is perhaps the largest — and most polarizing — social movement...