It is easy for even us low carb types to fall for the "meat is not sustainable" argument. An interesting talk by Dr. Peter Ballerstedt provides the opposite view that it is the "plant based" that is not sustainable.

Keto Salt Lake 2019 - 03 - Dr. Peter Ballerstedt: Getting to the meat of sustainability

https://www.youtube.com/watch?v=zemiuEwVpww&t=289s

A summary of his points copied from one of the slides in the Presentation slides link in the description:

1. Humans are heterotrophs. We must consume other organisms.

2. Animal products are superior sources of nutrition in the human diet.

3. Ruminant animal agriculture offers unique ecological advantages over other forms of food production.

4. There can be no sustainable agriculture without ruminants.

5. Ruminants are not competing with humans for resources.

6. Ruminants increase the quantity and quality of humanity’s food supply:
a. Animal protein is superior to plant “protein” in human nutrition.
b. Fats from animal products, especially from ruminants, are beneficial while
polyunsaturated fatty acids from plants have been shown to be harmful.
c. Minerals are more bio-available from animal sourced foods.
d. Providing essential nutrients unavailable from plant sourced foods.

7. Modern humans exist because of ruminants, modern societies depend upon them, and they will be essential to the future of humanity.

8. Estimates of ruminant animal agriculture’s environmental impact are typically overstated, over-simplified and misleading.