Above all, a Technician must be dispassionate. The Reality Change he initiates may affect the lives of as many as fifty billion people. A million or … - Isaac Asimov

Speech, originally, was the device whereby Man learned, imperfectly, to transmit the thoughts and emotions of his mind. By setting up arbitrary sounds and combinations of sounds to represent certain mental nuances, he developed a method of communication — but one which in its clumsiness and thick-thumbed inadequacy degenerated all the delicacy of the mind into gross and guttural signaling. — Down — down — the results can be followed; and all the suffering that humanity ever knew can be traced to the one fact that no man in the history of the Galaxy, until Hari Seldon, and very few men thereafter, could really understand one another. Every human being lived behind an impenetrable wall of choking mist within which no other but he existed. Occasionally there were the dim signals from deep within the cavern in which another man was located — so that each might grope toward the other. Yet because they did not know one another, and could not understand one another, and dared not trust one another, and felt from infancy the terrors and insecurity of that ultimate isolation — there was the hunted fear of man for man, the savage rapacity of man toward man. Feet, for tens of thousands of years, had clogged and shuffled in the mud — and held down the minds which, for an equal time, had been fit for the companionship of the stars.

Human beings, in terraforming a world, leave out the thorns and thistles, whatever they may be, and human beings then have to labor to keep the world going. It isn't a self-supporting organism as Gaia is. It is rather a miscellaneous collection of Isolates and the collection isn't miscellaneous enough to allow the ecological balance to persist indefinitely. If humanity disappears, and if its guiding hands are removed, the world's pattern of life inevitably begins to fall apart. The planet unterraforms itself.

You can't understand human motivation. You can only understand your damned machines because you're a machine yourself, with skin on.