The estimate is nonsense. Africa's population has trebled (or whatever) yet the green revolution never happened in Africa. The continent is overwhelmingly fed on pre-green revolution crops grown in pre-green revolution ways with low fossil fuel inputs. The old ways scaled up. (Though arguably at great cost to natural habitat.)

Certainly there would be many more farmers (less efficient) without this gent's green revolution advancements and the food would be more expensive, but it's baseless to assert everyone would have starved otherwise.