While we shouldn’t apply carrying capacity to human society, especially with the precedent for how ‘social’ Darwinism has impacted the most vulnerable, we need to be clear that a larger population will be a strain on resources, to the extent that habitat is displaced for other species.
I found Ian Angus’ book Too Many People? very helpful in understanding the nuances of population control rhetoric, and the history of population control attempts (not first world, wealthy people but always marginalized, people of color in the third world– the most vulnerable). This has occurred in places like India, leading to deaths and forced sterilization, despite how low their ‘footprints’ are compared to first world consumerist/resource-intensive lifestyles.
As others in this post have highlighted, the issue is distribution of resources + overproduction and overconsumption due to the current economic system. This system which is allowing such lifestyles to exist is premised on unequal exchange (as the systems ecologist H.T. Odum has shown using embodied energy (‘eMergy’)) between the first and third worlds, a phenomenon of ecological imperialism (or ecological overdraft in the case of rich nation) that is decimating biodiversity and habitat in South America, Asia, and Africa.
Population control rhetoric ignores this matter of resource use distribution (steeped in these economic dynamics) and necessarily what populations will be controlled & by whom. There are enough resources for everyone (if distributed equally) now to live a qualitatively fulfilling life once we recognize what we actually need, challenge the current dynamics, and truly put out needs in the context of other species/the environment. Only in the context of this, with a long term cultural shift (which is already occurring) in how we collectively perceive parenthood is discussing population meaningful. As Donna Haraway has put it: “Make kin, not babies!”