Q. How come the huge impact of our population growth on climate change doesn’t get more attention when we talk about how to take action against warming?

— Too Many Humans, Too Little Time

A. Dear TMHTLT,

There’s long been a contingent of environmentalists who love to point to the world’s population as a major factor in humans’ self-destruction. The logic seems basic: Climate change is caused by humans, so fewer humans should limit the harm of climate change.

The “optimal” global population to sustain ecosystems is considered to be between 1 and 2 billion. The actual population at present is a…