Please don't move the goal posts with CO2 output versus plastics pollution. They are two distinct issues. If you can apply pressure on CO2 and methane emitters to push down their emissions, I strongly encourage you to do so. First world countries have astoundingly good waste management systems though.

Whether the third world outlaws single use light weight plastic bags doesn't impact their poor waste management infrastructure. People will still throw garbage (plastic bottles, bottle caps, straws, plastic containers, plastic cutlery) in their rivers. Stop people from throwing garbage in rivers, regardless of composition. You're not going to be able to outlaw everything thrown into the rivers.

"Last year, a third of the 1.67 million tons of domestic waste disposed in Singapore consisted of packaging waste, primarily plastic bags and food packaging. The amount is enough to fill more than 1,000 Olympic-size swimming pools, according to a Channel News Asia report."

“Six million tons of non-durable plastics -- basically cutlery -- gets discarded every year. It is estimated that by the year 2050, plastic in the ocean will outweigh fish," he adds.

If you're going to outlaw single use plastic, outlaw all of it and mandate paper bags or other fiber products; you're still going to need to implement waste management, landfilling, etc.

https://www.forbes.com/sites/hannahleung/2018/04/21/five-asi... (Five Asian Countries Dump More Plastic Into Oceans Than Anyone Else Combined)