The logic’s there: Persuade Big Food buyers to band together to boycott a harmful practice, and their collective power will end said practice. But the irony’s there, too: some of the major reasons forests get cleared in the first place have to do with planting crops and grazing livestock. And how did Big Food get so big? Well, partially because corporations were able to buy mass-produced ingredients on the cheap, largely as a result of policies that encouraged widespread monocropping and incentivized meat production. Sounds a lot like having your hamburger and eating it, too–while sitting in a big, clearcut forest.

Charles points out a couple of problems with pledges to avoid harmful buying patterns. First off, some food companies use “where available” disclaimers to compensate for purchasing hot-button ingredients like palm oil, essentially building “get out of jail free” cards into the pledges. That’s not as totally evil as it sounds. Demand for sustainable palm oil outstrips supply, and forest-friendly versions are not always available (or cheap) enough to keep them on ingredient lists.

The second, trickier problem is that a lot of food companies don’t monitor the entire supply chain all that closely, or even at all. It’s similar to the problem well-intentioned corporations face when they try to eliminate slavery from the supply chain (we wrote about that set of obstacles here): If you want to make sure that not a single ingredient in your candy bar has been grown, picked, or processed using forced labor, you better have a pretty intricate set of inspections lined up to make sure you achieve that goal. Supply chain oversight requires a lot of time—and a lot of money.

So maybe Dunkin’ Donuts and McDonald’s are saving the trees, but also maybe they’re not. Happy election week.