That’s not what the paper says is the problem.

If you cant come to grips with the scientific fact that ecological destruction has a direct connection to population then you should start a special sub for CollapseMagicalThinking.

Life requires resources these resources have flow rates, for example the amount of human appropriated calories that are possible to grow in one m² is limited by things like sunlight temperature nutrient inputs etc… This is scientifically measurable and all creatures including humans are constrained by such things. We are also constrained by waste production and the rate of waste detoxification by ecosystem services.

Of course “affluence” as measured by consumption is also part of the equation P*A=environmental impact. Humans appropriation of global bioproductivity is already pushed the other life on earth into mass extinction. Its already reduced many areas to lower bioproductivity levels. Over 40% of our current population number is dependent on advanced synthetic fertilizers that are highly dependent on fossil fuels and other depleting resources.

High population doesn’t imply killing people. It can mean voluntary birth control usage and lowering the ability of the global 1% to engage in excessive consumption rather than killing the poor that use a tiny fraction of the resources per capita.