What he is saying is that the earth can't support the amount of people there are. True, it can't. Not without GMO and scary farming practices.
Environmental pressures will make this worse. True. Food aid as a solution is 'barmy'? True. Overpopulation and bad environmental choices cause famines. True.
I understand why people want to send food to a starving child. It's a natural reaction. But what happens is that we react to famines, rather than trying to prevent them. The economy reacts very poorly to food aid, local farmers suffer, end up in debt. They then can't buy what they need to help food security and more people starve. Africa's economy becomes dependent on aid and the West and we really can't be trusted to act in their interests (debt and tied aid for example) so more people starve.
DA proposes educating girls. Which leads to lower birth rates, less extremism, fewer wars, better educated children, better healthcare and all round a better world.
The only thing I disagree with him about is that overpopulation in Africa and Asia is the only problem. I think almost everywhere has too many people and the West consumes more per person by magnitudes so our population is 'worse' for the environment.
He's mostly right. He just isn't sentimental and he is scientific. That is very unpopular.