There has never been a better time for Latin American integration

IT IS Saturday lunchtime, and about 30 trucks are parked at each of the customs posts on either side of the bridge across the broad Uruguay river that marks the border between Argentina and Uruguay. Both countries are members of Mercosur, a would-be customs union that also embraces Brazil and Paraguay. In theory, internal borders should not exist in Mercosur. In practice, customs, sanitary inspections and other paperwork mean that the trucks are delayed for up to 24 hours, says Oscar Terzaghi, the mayor of Fray Bentos, on the Uruguayan side.

This represents an improvement. For three years before 2010, access to the bridge—the shortest land route between the two capitals, Buenos Aires and Montevideo—was blocked by Argentine environmentalists with the support of the country’s president, Cristina Fernández. They claimed that a planned paper mill at Fray Bentos would pollute the river. The dispute ended only when the mill was operating and the International Court of Justice ruled that there was no evidence of pollution.