From the Introduction
Hundreds of years ago, the empires of old lost touch with what the world offered them. She had cradled them since their birth, and now they killed her with their spinnings of heavy metals and toxic smoke. So when their thinking machines rose against them, they had no protector to fight back. But just as all seemed lost, the forsaken greenery fought back. But this growth knew neither friend nor foe, but struggled to protect itself. Humankind was a mere spectator in this struggle of the vengeful nurturer vs the created monstrosity.
But humankind was, if nothing else, adaptable. And the Green had no ill will towards them. So as greenery shrouded the Earth, obscuring the battles that raged on the planet, humanity built upwards, their tallest monuments their own refuge on a world where nature still battles against machine far below.
It is a hard life, where communities of the vestige of humanity struggle to eke out what existence they can, attempting to stay in the Green's area of benign regret- they have learned the hard way what happens when they draw her ire. These enclaves use only natural material and power to keep their communities alive, as vessels known as Cutters traverse the Canopy to trade and bring word to distant places and keep some sort of social construct of humanity together. But what they can gather on the treetops is not enough to survive, even in the meanest conditions. Sometimes, they need things from the plants below, or from the old ruins of the hubris of their ancestors. It's a hard but necessary job to keep humanity on the raggedy edge of extinction.