Most of the world’s grain is not eaten by humans

I see, thanks for the elaboration. You may be correct, but there is more nuance based on my reading of the report: in particular, the "agriculture" category is somewhat misleading. I read a bit of the report, so I might as well post my findings here :)

"Agriculture" appears to measure the emissions generated directly from agricultural processes themselves, as well as "secondary" combustion inputs. This includes "enteric fermentation in domestic livestock, livestock manure management, rice cultivation, agricultural soil management, liming, urea fertilization, and field burning of agricultural residues". However, based on my reading -- please correct me if I'm wrong -- large parts of the agricultural process are included in each of the transportation, electricity, and industry categories. Thus the effects of agriculture would be seen downstream and upstream in these other categories. For example, any agricultural use of electricity is included in "electricity", not "agriculture".

An aside on meat specifically: since meat production involves more inputs, such as feed, livestock, and additional processing, you would have to account for these when comparing to a non-meat diet. For example, every cow involves the transportation of the cow, the (industrial) production of fertilizers needed to grow its feed, the production of the materials to package the feed, the transportation of the feed to a facility for packaging, the transportation of the packaged feed to a farm, the transportation of the cow to a slaughtering facility, the refrigeration of the cuts of meat, etc. The emissions generated during these steps would belong to the transportation, industry, and electricity categories, not even counting the extra emissions included in the agriculture category. While all food production would have steps such as these, clearly there are more steps in meat production because there are more inputs.

Now, back to the original point of transportation versus agriculture: the report says that 25% of the transportation category is "freight" -- I believe the shipping I described above would be included in this. However, to your point, around 60% of transportation is due to passenger vehicles and light-duty trucks, which is quite significant and likely mostly personal use (rather than agricultural), and that's where changing transportation methods can make a difference. I'm too tired to find what percent of industry and electricity are related to the agricultural process, but you would need to calculate this and compare it to personal transportation use in order to get a fair comparison.

In my personal opinion, I think we should both reduce meat consumption and personal vehicle use. No need to pick favorites.

Or in 8 years, according to the 2030 Agenda.

Thanks very much for posting. I'd point out that the numbers from that very useful link are wildly, wildly different from what the parent commenter posted:

1. The graphs appear to be showing that 29% of the Earth's land surface is "barren land", i.e. deserts, glaciers, rocky terrain, etc. In 1900, 48% of the NON barren land was forests, so 34% of the Earth's total land was forested.

2. In 2018 the percentage of forested non-barren land was down to 38%, or 27% of Earth's total land.

34% to 27% of total land area from 1900 to 2018 is a major difference from the parent commenter's assertion of "In 70 something years we went from 60% forest coverage of earth's land mass to 30%".

Eh, beef, maybe, but the math basically comes down to: wheat, 4 million calories per acre, corn, 15 million. Take that 15 million calories of corn and feed it to chickens for a 3:1 calorie exchange and you've got 5 million calories of chicken per acre.

It's more complicated than that, but corn yields are so high that they can overpower the otherwise inefficiency of meat production.

Potatoes are as good as corn, and rice nearly so, but just from a land usage perspective chicken is no worse than eating wheat bread.

Black bean, bacon (turkey bacon, for me), and barley stew is my go-to Instantpot meal. I like to imagine I'm eating at a tavern in a vaguely D&D/Middle-Earth-esque setting. Sometimes I add turnips too.