A Chinese beach.
If human beings stopped reproducing altogether (theoretically) for the next twenty years, the world population would diminish by 1.1 billion. That number is based on the 2014 global annual death rate (CDR) of 7.89 per 1,000. That would leave a human population of around 6 billion twenty years from now. Maybe technology would be able to solve some of the current toxic effects of human overpopulation in twenty years. However, that is not the challenge.
The global annual birthrate (CBR) for the next 20 yrs will average around 17 per 1,000 per year. That figure, minus the crude death rate of 7.89 per 1,000, leaves a factor of 9 births per 1,000. The world human population will be at least 8.7 billion in 2035, based on current conditions. That is about a 22% increase in human population. That means 22% less of everything for everyone than we have now.
If the wealth of the planet continues to concentrate to a smaller and smaller segment of the population, the amount of energy, food and water resources left to the remainder will diminish drastically very quickly, perhaps within one generation. What will be the social implications? We are already experiencing those implications. Mass migration, war, water shortages and famine. Overpopulation is not an intellectual problem on paper. I believe the core issue of feminism is not reproductive rights, but reproductive responsibility developed through scientific sex education of children. Social compensation/security systems should be redirected to education and away from reproduction.