As a now grain farmer who grew up on a dairy farm, what I find more concerning is all of the crazy synthetic and mined resources we have to pour onto the fields in the absence of animals in order to be able to meet the world's demand for food.
Our production of "vegetarian food" grew up with the idea of having animals as part of rotation, but with the decline in demand for most meat varieties, economics do not allow those animals to be part of the cycle anymore.
Vegetarianism may be a solution for the long term society, but it seems like we have a lot of technical challenges to overcome in the meantime. Right now it looks like we are just trading one problem for another.
If anything, where there's been a slight reduction in one area of consumption (e.g. beef) there's been an increase in another (poultry) with an overall rise in meat consumption.
> economics do not allow those animals to be part of the cycle anymore
Given the incredible size of modern farms, using animals as a source of fertilizer is no longer practical. Meat consumption isn't really part of the equation - livestock require food themselves, so you'd need to grow huge sums just to feed the animals as well as produce enough grain/vegetables for human consumption. If you can artificially produce fertilizer then you remove this bottleneck.
Smaller farms would allow animals to be part of the rotation.
Our production of "vegetarian food" grew up with the idea of having animals as part of rotation, but with the decline in demand for most meat varieties, economics do not allow those animals to be part of the cycle anymore.
Vegetarianism may be a solution for the long term society, but it seems like we have a lot of technical challenges to overcome in the meantime. Right now it looks like we are just trading one problem for another.