Zero Population Growth is a process whereby the
population of any given
ecosystem is
constant. It stems from a
theory that the
earth has a certain '
carrying capacity,' and the
belief that we are either approaching that capacity, or that since we don't know what that capacity is we should stop growth until that number is known and understood.
One of many reasons someone might choose to support ZPG is the idea that it is
better for some people to live in
decent conditions than for many to live in bad conditions. This is, again, based on the belief that if population growth does not slow or stop then humanity will be subject, as a whole, to
abject poverty and hunger.
There are many studies supporting the positions of both sides of the disagreement as to whether there is a real problem, or whether it will become a problem in the next few
millennia. At this point it is simply a
lobbying effort that supports many initiatives aimed at slowing population growth, such as
womens rights (
abortion,
contraception, etc), UN efforts for
human rights (aimed at making all countries nice to live in to reduce
immigration), and a broad
public awareness effort (
propaganda) to
sway popular opinion towards treating the earth as a
zero sum resource.
ZPG may refer to the system of beliefs surrounding zero population growth, or it may refer directly to the organization (US based) of that name.