The Guild knew more about Arrakis ecology than anybody else except the Fremen after Kyne. They also knew that to meddle with the planet is to take massive socio political risk. They were quite content letting the Fremen, Landsraad, and the Emperor fight over it as long as the spice flow. But they did betray the Fremen bribe when the ecological change they were making became clear to them. >The Guild is like a village beside a river. They need the water, but can only dip out what they require. They cannot dam the river and control it, because that focuses attention on what they take, it brings down eventual destruction. The spice flow, that's their river, and I have built a dam. But my dam is such that you cannot destroy it without destroying the river.
from overview for madhi19 http://ift.tt/1oYZADg