Complex sentence: Agrarianism on a small scale is an idealized dream of choice for many, but to implement on a large globally effective scale require force and massive scale population reduction/genocide that kills some 70 to 90% of the global human population.
Split into simpler sentences: Agrarianism on a small scale is an idealized dream of choice for many, but this does not extrapolate up easily. To implement agrarianism on a large globally effective scale requires force and massive scale population reduction/genocide that kills some 70 to 90% of the global human population.