If I source my beef or lamb from low-impact producers, could they have a lower footprint than plant-based alternatives? The evidence suggests, no: plant-based foods emit fewer greenhouse gases than meat and dairy, regardless of how they are produced.

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Plant-based protein sources – tofu, beans, peas and nuts – have the lowest carbon footprint. This is certainly true when you compare average emissions. But it’s still true when you compare the extremes: there’s not much overlap in emissions between the worst producers of plant proteins, and the best producers of meat and dairy.

https://ourworldindata.org/less-meat-or-sustainable-meat