I may be speaking under correction here, but arable land doesn't equal agricultural land. The 0.5 hectares per person cited is (afaik) for total agricultural land. A typical American diet actually uses around 1.08 hectares per person with around 0.34 hectares being cropland (arable land) and the rest being grazing land. An ovo-lacto vegetarian diet uses 0.12 (arable land) + 0.02 (grazing land) hectares per person (assuming no excess intake) and a completely vegetarian diet (with no excess intake) uses only 0.13 hectares per person (only arable land can be used though). This should mean that using all of the world's current arable land (1.873 billion ha) our maximum population limit, assuming no future land degradation and perfect harvest practices would be 14.4 billion people on vegetarian diets.
2
u/DanieB52 Oct 25 '20
I may be speaking under correction here, but arable land doesn't equal agricultural land. The 0.5 hectares per person cited is (afaik) for total agricultural land. A typical American diet actually uses around 1.08 hectares per person with around 0.34 hectares being cropland (arable land) and the rest being grazing land. An ovo-lacto vegetarian diet uses 0.12 (arable land) + 0.02 (grazing land) hectares per person (assuming no excess intake) and a completely vegetarian diet (with no excess intake) uses only 0.13 hectares per person (only arable land can be used though). This should mean that using all of the world's current arable land (1.873 billion ha) our maximum population limit, assuming no future land degradation and perfect harvest practices would be 14.4 billion people on vegetarian diets.
This is based on my understanding from this paper: https://www.researchgate.net/publication/305627253_Carrying_capacity_of_US_agricultural_land_Ten_diet_scenarios
The 1.873 billion ha figure comes from the USGS and NASA project, GFSAD30, that measures global land use:
https://croplands.org/app/map/finalmaps#Mosaic