Environmental doom, sauteed to perfection. (Bill O'Leary — The Washington Post) Trying to eat sustainably is a maddening, thankless task. It’s hard enough keeping track of which foods have higher carbon footprints than others — cheese and farmed salmon are worse than chicken but not as bad as lamb — and there are invariably unpleasant surprises tossed into the mix. Case in point: Tom Philpott reports that some types of shrimp, of all things, can have an exponentially higher carbon footprint than beef:

Mangroves, it turns out, are rich stores of biodiversity and also of carbon — and when they’re cleared for farming, that carbon enters the atmosphere as climate-warming gas.

[The University of Oregon’s J. Boone] Kaufman estimates that 50 to 60 percent of shrimp farms occupy cleared mangroves, and the shrimp that emerges from them has a carbon footprint ten times higher than the most notoriously climate-destroying foodstuff I’m aware of: beef from cows raised on cleared Amazon rainforest.

Keeping all these issues straight would be a lot easier if there was a global price on carbon, and forests and mangroves were priced according to the ecological benefits they provide. (See this old story of mine for more on how that might work.) Then the worst-polluting foods — like Taco Bell’s factory-farmed Pacific Shrimp Tacos, say — would cost the most on the menu, while the most sustainable foods will be cheapest. Since we don’t have anything like that system, shrimp surprises will keep popping up.