I love Ezra Klein's posts on Food and his Posts on the Environment but I am very puzzled by this post on food and the environment.
You write " food ... more sustainable, organic, ... more healthful." This is not the first time that you assert or suggest in this blog that organically grown food is more healthful than food grown with the use of synthetic organic chemicals.
Are you aware of any evidence that supports this claim ? I am not.
Also what is wrong with farmed Salmon ? I consider it more green to raise fish then kill them than to depopulate the Oceans. I think that, in practice, is the alternative we face.
Also fish farms in the open ocean (which don't exist but could) would reduce global warming by enriching the ocean with nutrients (what the vulgar call fish shit) leading to growth of more phytoplankton and more carbon containing detritus falling to the bottom of the sea for the indefinite future.
I mean why is the Earth so much cooler than Venus. It's not because Carbon is sequestered as coal or petroleum or even as wood. It is because carbon is in limestone which once was phytoplankton and whose production depends critically on phosphorus (or maybe nitrogen) in the open ocean.
That which is very destructive in a harbor or bay (where actual fish farms exist) is beneficial in the open ocean.
To be green, I think the question is not what to do but where to do it.