"And keep in mind that this doesn’t scale very well due to the massive land it requires. Already clearing land for pastures is a large deforester. Trying to even scale to a quarter of beef demand would require using 100% of grassland which would put enormous pressure for further deforestation."

Most deforestation is intended to produce land for crop farming. There is still a lot of agricultural land left that is ideal for grazing, and that cannot be used for growing crops. We may not be able to feed everyone in the world on meat, but we definitely can't do it with plant-based foods alone.

And apart from that issue, there is the matter of protein quality, which is complicated to assess. Most mentions of plant protein are referring to total nitrogen content ("crude protein"), but not all of that comes as amino acids, which is the only form in which nitrogen can be assimilated by the human body.

So mixing and balancing plant protein sources has to be done with a certain amount of skill and care, because if one of the essential amino acids in the mix is deficient, that limits the assimilability of the rest of them.

[–] usernamesAreTricky@lemmy.ml 1 points 1 year ago* (last edited 1 year ago)

Extensive cattle ranching is the number one culprit of deforestation in virtually every Amazon country, and it accounts for 80% of current deforestation

https://wwf.panda.org/discover/knowledge_hub/where_we_work/amazon/amazon_threats/unsustainable_cattle_ranching/

Plant-based food production uses less cropland

The research suggests that it’s possible to feed everyone in the world a nutritious diet on existing croplands, but only if we saw a widespread shift towards plant-based diets.

[...]

If everyone shifted to a plant-based diet we would reduce global land use for agriculture by 75%. This large reduction of agricultural land use would be possible thanks to a reduction in land used for grazing and a smaller need for land to grow crops.

https://ourworldindata.org/land-use-diets

Complete proteins matter doesn't really matter all that much in practice. Things like soy are complete on their own, and things that are technically incomplete proteins like beans can be made complete with rather little like even rice. You don't need to be getting every amino acid in with every meal. If you eat the amino acids at some point in the day, you will be fine