QuoteWorld population growth is going down, and is currently nearly static in high and middle income countries (it would actually be negative without immigration, looking at birth rates; nearly the entire first and second world are below replacement fertility rates).
Sure, growth is slowing down, but it's still growing. I've heard that we're due to level off at 11 billion. My point is we're overextended RIGHT NOW. We're having increased global deforestation, half of all wildlife has been eradicated since the 70s, ocean health is getting worse and we're STILL GROWING. Here are some sources on the ecosystem being diminished:
https://www.theguardian.com/environment/2019/sep/12/deforestation-world-losing-area-forest-size-of-uk-each-year-report-finds
https://www.theguardian.com/environment/2018/oct/30/humanity-wiped-out-animals-since-1970-major-report-finds
https://www.climatechangenews.com/2019/09/25/dying-oceans-rising-faster-predicted-un-warns-stark-report/
As for the socialism v. capitalism thing, I'm not saying either would preserve the environment. My point is I think the very core of capitalism makes it impossible. The purpose of capitalism is to maximize profit for those with capital, correct? That means exploiting any and all resources. Taking a more reserved approach means you fall behind and can lose competitively to those who are more aggressive. This means almost maximum use of resources. Socialism doesn't necessarily mean that. It CAN mean that, like you mentioned, with fulfilling quotas, and collectively agreeing to come to a similar outcome.
My point was neither one obviously solves the problem, though capitalism appears to accelerate the problem as much as possible.