I also recommend this excellent 2011 article by a committed carnivore who drastically reduced his meat consumption: British chef Hugh Fearnley-Whittingstall.
The joy of veg https://www.theguardian.com/lifeandstyle/2011/aug/26/hugh-fe...
The joy of veg https://www.theguardian.com/lifeandstyle/2011/aug/26/hugh-fe...
At least in the US, the percentage of calories of a typical diet is 70% plant-based (including nut/vegetable oils) vs 30% animal, and I believe red meat has been on the decline for years, whereas consumption of chicken has risen.
https://www.ers.usda.gov/amber-waves/2016/december/a-look-at...