Here is a very long article by Michael Seebeck about the overpopulation/overconsumption debate: michaelseebeck.substack.com/p/overpopula...
He makes some excellent points. Truth is we are so overpopulated that sustainability is no longer possible, even with a vegan diet.
michaelseebeck.substack.com
Its both, but only one aspect is realistically amenable to correction.