For Ivorian police commissioner Luc Zaka, 2021 was an especially good year. He and his team rescued more than 1,750 children from harsh work on the country's cocoa plantations, and helped put several traffickers behind bars.

"We had to do everything possible to ensure our cocoa is quality cocoa that is not produced by children," said Zaka, who heads a specialist unit fighting child labour in Ivory Coast — the world's biggest cocoa supplier.

Named International Year for the Elimination of Child Labour, 2021 was meant to boost such efforts to stamp out the practice. But despite some success stories like Zaka's, global progress was patchy and COVID-19 fueled abuses, experts say. In Ivory Coast, where close to 1 million children still work in the cocoa sector, rescue operations have multiplied in recent years following pressure over labor exploitation from EU lawmakers and ethically-minded chocolate consumers.