Also the old shopping bags were extremely thin. The new ones in countries that implemented the tax are much thicker. So what exactly is the net plastic here? What about including plastic tote bags? I know they are reusable, but how many times do you need to use a very struby plastic bag until you reach net plastic?
LDPE (thicker, 'bag for life' etc) is about 4 times as bad, paper bags 3 times, vs HDPE (thin) bags assuming no reuse. The below UK gov study investigates impact of each (and other alternatives like cloth bags) and also considers reuse as bin liners, which significantly changes the numbers.
The thinner ones like to fly away, get carried long distances by wind or water, and will shred and tangle around things spontaneously. They are much more of a danger to wildlife than the thick ones for this reason alone. Shifting the bag away from "disposable" and "single-use" category makes a difference on its own in terms of how much of it ends up in the environment.
