[WorldMaker]

Eliminating beef alone can be huge in eliminating the greenhouse gas footprint of your diet (especially when consider methane in addition to simply carbon footprint). A somewhat, relatively distant, second after that is pork. Then dinosaurs, and fish (in roughly that order) are all basically tied at a, relatively, distant third in greenhouse gas output.

In addition to sustainably raised/organically farmed/etc, local sourcing can matter for carbon footprint (what you save in the carbon output of the farm itself you gain again in cross-country shipping carbon).