Chris Preston wrote: ↑Thu Jan 30, 2020 3:28 am
There is in fact a lot of complexity involved in the idea that the world would go vegetarian. As a simple extrapolation, I would note that doing so would lead to an increase in the area required for crop production.
With a corresponding decrease in the area required for meat production, of course. All the detailed analyses I've seen show a reduction in total area of agricultural production with increasingly plant-based diets. Are you singling out cropland for a reason?
While the world technically is growing enough food to feed itself, if we didn’t feed all that grain to animals, the reality is not so (even including food waste in the discussion). The reason being that a lot of the food grown is the wrong sort of food. The world has become very good at growing calories, but much less good at growing plant protein.
Changing the world’s diet to plant only would mean a shift of protein sources from meat to plants. The Green Revolution resulted in more than doubling the yield of cereals/ha, but had almost no effect on the yield of pulse crops. In the same fields cereals will typically out yield pulse crops by a factor of 2 to 3. For example, average soybean yields in the USA are 3.3 T/ha, average corn yields are 10.5 T/ha. It turns out that increasing harvest index has been simple for cereals (grasses) but is really hard for other types of crops. No doubt more work could be funded to try and achieve this, but there is no guarantee that the same yield gains will occur.
Also there is the issue of protein content. Comparing chicken to chickpeas, you need to consume roughly 3 times in weight as much chickpeas to get the same protein content as chicken. Using the Australian Government Recommended dietary intakes as a place to argue from, if you shifted 1 person from meat to pulses for protein, you would have to grow 0.26 extra T/year of chickpeas to accommodate that. Moving just 1 million people from meat to chickpeas would require an extra 260,000 T of chickpeas/year or an extra 79,000 ha of chickpea production. That is assuming the chickpeas could be grown on the best arable land. If they were produced on new marginal land, more area would be needed.
This is interesting, and I don't know much about agronomy etcetera. But even without improvement,
pulses yield similar amounts of protein per unit area to cereals, and far more than meat, with beef being roughly the least efficient producer of protein per unit area. (The results are qualitatively similar for calories per unit area)
You don't seem to mention what happens to the corresponding land used to produce all those chickens and their feed. You could grow chickpeas on it and have some left over, according to the models.
Much of the argument that is often made about growing crops to feed animals and how wasteful that is, is based on North American production systems where a large amount of grain is fed to animals. In most other areas of the world, this is not the case. Animals are pasture grazed, fed on crop residue and only occasionally supplemented with grain (many times not at all). Removing animal production would free up grain for human consumption in North America, although by less than people claim (see my comments above), but would have negligible impact in other parts of the world and increase the area required to grow protein crops. In many places, animal production occurs on land that is not suitable for crop production, so this land would have to come from somewhere else.
Yes, large areas marginal land would probably revert to forest, which would be a Good Thing, even if it required the loss of a smaller area of forest to increase crop production. The people modelling global land use requirements all seem to conclude that plant-based diets would be a much more efficient use of the world's area, even if it would require some reconfiguration of where things are.
However, studies like this (my bold):
We find that, given the current mix of crop uses, growing food exclusively for direct human consumption could, in principle, increase available food calories by as much as 70%, which could feed an additional 4 billion people (more than the projected 2–3 billion people arriving through population growth). Even small shifts in our allocation of crops to animal feed and biofuels could significantly increase global food availability, and could be an instrumental tool in meeting the challenges of ensuring global food security.
don't seem to share your conclusion that increasing total cropland area would be necessary. Their level of detail seems reasonable (41 major crops) and the FAO's data on allocation should be robust enough? What are we missing?
The recent
EAT Lancet report, which was combining Rockstrom's planetary boundaries concept with optimising for nutrition, also came in favour of a largely plant-based diet.
While I am all for eating less meat, and particularly less red meat (actually I had my first steak (rare of course) in over 12 months on a recent holiday), meat free diets are not going to save the world from greenhouse gas emissions.
I was hoping to find a more recent set of data, but this is what an easy search came up with. This figure divides greenhouse gas emissions up by both gas and source. The main sources from animal agriculture alone (leaving aside the transport and crop production values, which ironically would both increase if eating animals was done away today) are CH4 from agriculture, where animals contribute about 2/3rds (the rest is from rice) and N2O from agriculture, where animals contribute about half. Compare those with the other sources and it becomes pretty obvious where the biggest gains could be had. That doesn’t mean the gains from reduced animal production should not be had, it is just they are much smaller than the average person thinks and won’t be nearly enough on their own.
For sure, changing agriculture is only part of the solution to climate change. It's probably more important in addressing the biodiversity crisis. As well as water resources, nitrogen pollution, phosphorus pollution, and some people would also highlight the ethical aspects, but I think that's an unnecessary derail
We have the right to a clean, healthy, sustainable environment.