In the intervening five decades since the first Earth Day, we 3.7 billion people of 1970 have more than doubled to 7.8 billion.
What will happen if present-day birth rates continue? Though the detailed future of the human species is impossible to predict, basic facts are certain.
The answer, of course, is universal access to contraception and safe, legal abortion, as scientists have been recommending for over 50 years.
Mass extinctions involve a catastrophic loss of biodiversity, but what many people fail to appreciate is just what "biodiversity" means.
Changing the 'status quo' to properly address both growth in human population and consumption is a difficult challenge.
The growth of human numbers is the root cause of all planetary ills. Recognition of human population limits still awaits world leaders action!
We are now in what might be dubbed the lugubrious age - defined here as a sorrowful time for many places in the world.
Failure to implement a global sustainability plan that addresses excess consumption and over-population may well be fatal to global civilization.
For all the human development, something else had to give. That something is the living planet we all inhabit as well as the non-human species.
Women around the world would like either to have no more children or not to have more children in the next couple of years.