Clearly, to reverse plastic consumption growth by mid-century, the plastics treaty will need to stipulate more stringent measures and conditions than we have factored into our model. For example, the phasing of bans on single-use plastic products in countries will likely need to be faster and on a steeper trajectory than we’ve assumed. And a tax on virgin feedstock—that is, derived from fossil fuels—in the upstream production of plastic will also need to be higher.

Implicit in our scenario analysis is that bans and limits to plastic demand growth due to higher retail prices will motivate industry to push harder on technological innovation. Such innovation must, for example, bring about the redesign of packaging and products that contain little or no plastic. The capabilities of sorting and recycling technologies must also advance to ensure that all recyclable plastic is actually recycled.

No one should underestimate the opposition that such measures are likely to encounter from some producers, retailers, industry bodies, consumer groups or other actors, even if the world’s major stakeholders have signed on to them.

This makes it all the more important that the treaty also addresses monitoring and enforcement. Experience suggests that potential loopholes that would undercut the achievement of targets are numerous. For example, EPR schemes—particularly in low-income countries—will need to be closely monitored at city and regional levels. Fines imposed on producers, industrial consumers or retailers will need to be stiff enough to enforce compliance, and must be enacted at the highest government level possible.