They say any available evolutionary niche will eventually be filled by some enterprising mitochondrial strain. The human race had bulldozed most of those niches, paved them over and started charging rent.

The dirt from felled mountains had to go somewhere, of course, so into the oceans it went, and more land ripe for the building was the result. The water was desalinated for drinking, or split into vast hydrogen and oxygen reserves for the fuel cells that powered the cities, and the rest, with a little help from the increased heat output of the ever expanding, ever demanding human race, escaped into the atmosphere; a global, roiling storm that stretched from pole to pole. The rain was unceasing. Unending. The only escape from it was to be safely indoors, under a nice sturdy roof.

Roofs, therefore, were humanity’s next great endeavour. What had been cities became city, and then building. The animals had no choice but to move indoors. To adapt. There was space for them, too, in the foundations and breezeways and refuse dumps and reservoirs. The places where humans no longer had any real need to tread. The carnivores went on living much as they had in their new environs. The herbivores adapted quickly. Organic was organic after all, and the understreets were full of the leftovers of locally-lab-grown produce, cave mosses and lichens that were secretly quite pleased about the recent (to a lichen’s way of thinking) changes about the place, and of course the libraries.

Nobody had much known what to do with the libraries. They weren’t strictly needed anymore, of course. Every known scrap of writing had long since been digitised, down to the drunken scribblings of names and phone numbers on the back of bar mats. The most stalwart of book lovers was hard pressed to tell the difference between the feel or even smell of the current electronic readers and the real thing. Of course there were rarities and personal favourites in private collections all around the world, but when it came down to it there were, in the pages (if you will allow me that) of human history, vast swathes of literature, self-help books and recipe collections that were objectively not worth the paper they were printed on. Still, burning them seemed rather totalitarian, and so the libraries had simply been closed, the librarians given new jobs shushing people at funerals or movie theatres, and the building went on around and eventually over them.

They were the new forests. It was as if all that paper had suddenly decided to become trees again. As if the potential had always been there. Exploratory book-finding parties led by rich eccentrics desperate to find and save last remaining signed first editions of this or that were seldom heard from again. The floors were littered with leaves and folios, stalked through by big cats dark as ink. High in the stacks primates capered, and in the rafters brightly coloured birds built nests from pages of picture books.