No matter how many “scientific” “facts” environmentalism is based upon, there is no right answer for how things should be done. Take, for example, grocery bags. 15 years ago, we switched from paper bags to plastic bags because it was good for the environment (you know, gotta save those trees!). Now we’re supposed to switch from plastic bags to paper bags because it’s good for the environment.
In other words, environmentalism, just like high school, is little more than a popularity contest.

Isn’t science based on hypothesis, experimentation and observed facts and data? If the data doesn’t support your previous hypothesis, then you adjust your assertions and conclusions.
Original hypothesis: paper products are detrimental to trees. Trees are being cut down at an alarming rate. Therefore paper is probably worse than plastic.
Testing proves: paper products are cheaper and cleaner and spur the planting of more new trees (due to increased demand). Not to mention, trees are a renewable resource, where petroleum products are not.
Revised hypothesis: paper demand creates more trees just like ethanol creates more friggin corn (but let’s not go there). Plastic bags require petroleum and are not renewable or recyclable (to whatever dubious extent anything beyond metals are recyclable). Paper degrades naturally where plastic bags are destined for a 6 month stint under your sink until you finally decide that you can’t possibly use them for anything else and you throw them away.
Seems like good science to me.
The thing that always bothers me is that, of all the legitimate environmental issues to devote time, money and energy to, why grocery bags? Is it because they’re so tangible and everyone comes into contact with them? Are grocery bags a gateway issue that gets people aware of other, more pressing, causes?