Almost all conventional/industrial agriculture (plant or animal based) is unsustainable due to the external inputs required (70% from fossil fuels for growing corn! [1]), soil depletion incurred [2], and just plain shipping things around. [3]
The alternative is local regenerative agriculture [4], which the Rodale Institute [5] and a recent Quantis (non-peer reviewed) studies [6] point to being potentially carbon net negative due to carbon soil sequestration via regenerative grazing. It also appears to be more economically sustainable [7][8] and can provide competitive yields [8].
For those interested in reading more, I found a couple pretty lengthy (peer-reviewed) academic reviews on the topic to be pretty fascinating:
Rhodes, Christopher J. “The Imperative for Regenerative Agriculture.” Science Progress 100, no. 1 (March 1, 2017): 80–129. https://doi.org/10.3184/003685017X14876775256165.
Teague, W R. “FORAGES AND PASTURES SYMPOSIUM: COVER CROPS IN LIVESTOCK PRODUCTION: WHOLE-SYSTEM APPROACH: Managing Grazing to Restore Soil Health and Farm Livelihoods1.” Journal of Animal Science 96, no. 4 (April 2018): 1519–30. https://doi.org/10.1093/jas/skx060.
Pretty, Jules. “Agricultural Sustainability: Concepts, Principles and Evidence.” Philosophical Transactions of the Royal Society B: Biological Sciences 363, no. 1491 (February 12, 2008): 447–65. https://doi.org/10.1098/rstb.2007.2163.
Pearson, Craig J. “Regenerative, Semiclosed Systems: A Priority for Twenty-First-Century Agriculture.” BioScience 57, no. 5 (May 1, 2007): 409–18. https://doi.org/10.1641/B570506.
[1] https://www.wur.nl/en/show/Can-conventional-agriculture-feed...
[2] https://www.scientificamerican.com/article/only-60-years-of-...
[3] https://www.nytimes.com/2008/04/26/business/worldbusiness/26...
[4] https://en.wikipedia.org/wiki/Regenerative_agriculture
[5] https://rodaleinstitute.org/wp-content/uploads/rodale-white-...
[6] https://blog.whiteoakpastures.com/hubfs/WOP-LCA-Quantis-2019...
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5831153/
[8] https://rodaleinstitute.org/science/farming-systems-trial/