Over three decades ago, the BND meme was born. Conceived by artist Ted Dave, the ritual sprang out of the realization that addiction-forming advertising had polluted our mental environment, and it was killing not only our wallets but our culture, our souls, our planet. Hence the one-day challenge to "participate by not participating."

A handful of years later, we rescheduled it to fall on the all-American consumption blitz of Black Friday. Riding the wave of an early viral campaign, soon the annual shopping moratorium was being observed in over five dozen countries. Then, the meme mutated from a single day to a whole season: Buy Nothing Xmas was brought to bear on the emptiness and waste of the modern yuletide holiday.

And then it mutated again. Now, in over 6,500 Facebook groups across 44 nations, millions are living by its tenets every single day. They share tools, clothing and food, hand-made goods, hand-me-downs, and everything in between. Buying, selling, trading and bartering are all strictly forbidden.

Welcome to a cashless, wireless, wasteless world.

From a single day to a season-long tradition to a daily habit — Buy Nothing has evolved from a crazy idea to a widely practiced way of life. No leaders, no capital, no outside meddling: with nothing but numbers and the spark of a great idea, it has revolutionized the lives of millions — and potentially the warming world.

After three generations of Buy Nothing, what will the fourth look like? Will it dig deeper, move further, adapt faster? Can it be wielded with force against climate change, putting humanity onto a sane sustainable path?

The answer starts with a single day.