The mounting strains on global shipping

There is no mistaking, on entering the port of Algeciras, at the southernmost tip of Spain, how busy the facility is. The cranes that tower above the port's two container terminals are nearly all at work, shuttling containers on and off ships.

The piles of boxes in the terminals' yards are mainly stacked the maximum five high. Alonso Luque, chief executive of TTI Algeciras, operator of one terminal, says that this year he has turned away far more requests to handle extra cargo than he has been able to accommodate. "You can see that the capacity is quite limited," he says, gesturing at the stacked containers.