Imagine bacteria and fungi breaking down all the plastic into CO2. Don't know which is lesser evil: plastic as it remaining in the environment or more CO2 but less plastic?
edit: just to make sure that my guess wasn't too far off, I looked up some numbers: we relase about 8 million tons of plastic into the ocean every year. Burning 1 units of plastic produces 3 units of CO2, giving 24 million tons of CO2 if all that plastic were broken down by fungus (or incinerated). We release around 35 billion tons of CO2 every year from burning fossil fuel.
https://www.sciencedirect.com/science/article/pii/S254243511...