The failure of recent global talks in Busan, South Korea, to produce a landmark treaty to combat plastic pollution, has underscored the complexities and challenges of addressing one of the planet’s most pressing environmental and climate issues.

The UN environment chief insisted Monday that talks on a landmark plastic pollution treaty were not a failure, saying important progress was made despite negotiations collapsing without agreement.

Countries negotiating a global treaty to curb plastic pollution have failed to reach agreement, with more than 100 nations wanting to cap production while a handful of oil-producers were prepared only to target plastic waste.