One of many websites on this issue http://www.worldpopulationbalance.org/3_times_sustainable
I have not seen much discussion here on RDFRS on the subject of sustainable population projections, or on the ways to attain the necessary reduction in population that is needed for a viable future for Humanity past the year 2100. Most predictions on sustainable LONG-term population size is between 1.5 to 2 billion humans.
I think that the main reason is that the path we are on is now so scary that we are unwilling to contemplate the outcomes, and are therefore more concerned and vociferous about the many symptoms that are the result of this core problem.
One of the main reasons that I am an anti-theist is that when I was a Scottish teenager in the 1960's I read about the Club of Rome and their predictions about 'The Limits To Growth'. As a secular humanist by upbringing, I read more and came to understand that the main barrier to limiting, or reducing, global population was societal ignorance and avoidance of the implications – attitudes driven by all the main religion businesses, which strive to increase their own group size so they can outnumber the others in their quest for survival and domination - thus driving me to become a convinced atheist, then a strong anti-theist.
These policies include the intransigent opposition to equality of women, banning of contraception & abortion, state subsidies for producing children, religious indoctrination & education, religious interference or domination in local, regional & federal governments, and religiously infected state policies & laws.
We are becoming more aware of the consequences and implications of doing essentially nothing for the past 50 years since humanity became aware of our life-threatening trajectory, but we are consumed with kicking around the symptoms and mostly avoiding the overpopulation problem that drives all our mounting issues – whether they be CO2 production, climate change, resource depletion, water and oil depletion, desertification, deforestation, fishery collapses, ocean acidification, contamination from waste products & effluence, extinction of species, along with various conflicts and wars exacerbated by very dense societies.
How can we as a secular community make our voices heard more about this core problem, without being deemed to be just a bunch of doomsayers?