Concerns about overpopulation have long been used as an argument for allowing or promoting abortion. Today this argument is used mainly at the global level to support an international abortion agenda pushed by the United Nations Population Fund and others.
(President Obama's science czar, John Holdren, offered the overpopulation argument back in the 1970's.)
Population control as a justification for abortion clearly begs the question as to the moral status of the unborn. If the unborn are valuable human persons, then killing them because we think the planet is too crowded is certainly wrong, just as killing off other segments of our population for the same reason would be wrong.
In any case, overpopulation is a myth.
