This is the unprecedented and presently irreversible explosive growth, dispersal, and concentration of human populations. There are few real environmental, economic, and social problems that would not ultimately be significantly eased if world populations were stabilized below present and projected levels. The interactions of population, resources, environment, and the economy are complex and controversial. If society overshoots the limits of sustainability, retrenching to a stable state would likely be painful and disruptive. Whether democracy and individualism as we know them could survive a reverse transition is, at least, questionable.
Numbers count in numerous ways.
But continuing human preemption of physical space, habitat, and natural resources seems certain to destroy the living world within which humanity evolved. It is plausible that human populations are today too large to sustain indefinitely their present demands upon the planet. Yet their numbers are projected to grow into the coming century and their demands upon the Earth to increase. Reproductive practices that served humanity during past centuries have now become counter-productive for humanity as a whole, and are the major force driving the environmental future over which humans, in principle, have control. At some point the adverse effects of overpopulation seem certain to stop, stabilize, or reverse population dynamics.