You see a sudden drop to 0.6 ha/person after 1960 due to green revolution which is soil-destroying and nonviable in the post-fossil age of which we’re in early stages of but which will progress quickly. So this and carrying capacity degradation will increase the ha/person footprint which means famines, which will first happen in the more vulnerable populations you mention. This will result in a lot of excess deaths which will eventually bring down the world population to whatever sustainable carrying capacity level it will then be. Worst case we’re looking at 100 million or below. If we’re lucky this will happen over a long period so that the excess death burden is not crippling.