From Evan Eisenberg’s The Ecology of Eden:

Half a million years ago, our genus formed an alliance with perennial grasses which allowed us to conquer the world. Over the past ten thousand years, an alliance of humans and annual grasses has conquered much the same ground in a fraction of the time, displacing or subduing not only other species but other humans, their allies, and their cultures.

Only a few centuries ago, a third alliance arose which is now very close to total hegemony over the living world. It has displaced or subjugated much of the natural world that survived the first two waves, as well as what was left of the waves themselves, including humans, their allies, and their cultures. The odd thing about this third alliance is that our most important allies have been dead for millions of years. They are cycads, ferns, giant horsetails, mollusks, plankton, and other creatures that flourished in the Mesozoic and Paleozoic eras, and which the bear-hug of the earth’s crust has crushed into energy-rich carbon compounds.

Modern humans are merely the latest in a long and distinguished line of saprophages: creatures such as fungi, maggots, and various microbes that feed off decaying or decayed organic matter. In our case, the dead organic matter in question is wood, peat, coal, and oil. [. . .]

An oil spill is a kind of night of the living dead, in which dead organic matter that we have called from its grave rises and strangles the living. But oil spills are the least of the problems that fossil fuels cause. For species not allied with man, this third wave is a horror show in which their own ancestors come back to haunt and harm them. Whatever humans could do before–strip forests, rip up soil, move themselves and their allies to the outermost corners of the world–they can now do more easily. [. . .] The earth is punctured, gouged, and scraped to get at more fuel, and at the minerals that are used to make the machines that use the fuel. [. . .]

A biologist from a pedestrian planet, peering at some stretch of North America from a height of five hundred feet, will conclude that its dominant species is a shiny lozenge-shaped reptilian creature that alternately basks in the sun and sprints at great speed. It is host, he will note, to small endosymbiotic organisms which at intervals emerge, move about slowly, then re-enter the host. Further observation reveals why the host puts up with these seeming parasites. They are devoted to the care and feeding of the host. They suck energy-rich organic compounds from the bowels of the planet and feed them to the host, something it is unable to do for itself. At times they even fight other colonies of their own species for access to the host-food. They make over ecosystems to meet the host’s needs, replacing vast forests and grasslands with flat surfaces on which the host can bask or sprint more easily, and building hives or dens in which the host can take shelter from the elements. What they get in return is as yet unclear. Indeed, it seems possible the two organisms are forms of the same species, the lozenge being a sort of queen and the smaller creature a worker.”