We Can Dance Around Environmental Problems All We Want. We Eventually Reach Overpopulation and Overconsumption: https://shows.acast.com/leadership-and-the-environment/episo....
https://www.cnn.com/2020/07/14/world/world-population-shrink...
Overpopulation or Underpopulation by Toby Ord
https://www.youtube.com/watch?v=r7LgGylpI9U
A rough snippet: note that hammers and songs are different. Hammers are made of matter and require labor. Songs are a pattern and can be copied virtually for free. Songs are more valuable when there are more people: greater total enjoyment. And having more people means more minds to create great things. Some things like computers are so complex that they require a large population to make. Smaller populations might not yield the amazing technology we could otherwise have.
https://www.youtube.com/watch?v=2LyzBoHo5EI
I'm sure it won't convince all of the Malthusian doom and gloom sorts, but it's worth a try.
The easiest way to avoid overpopulation is to establish equality for women.