Overpopulation has been a threat to the planet since long before anyone heard of climate change.

English economist Thomas Malthus first sounded an alarm about the potential for population growth to overwhelm the planet's natural resources in 1798. The alarm rang again in 1968 with Paul Erlich's doomsday treatise "The Population Bomb," and has reverberated since in the background of the climate crisis: All else being equal, more people means more emissions, more hungry mouths, more potential victims of natural catastrophes.