Children of Dune by Frank Herbert
The sand-blasted desert world of Arrakis has become green, watered and fertile. Old Paul Atreides, who led the Fremen to domination of the galaxy, is gone. But for the children of Dune, the very blossoming of their land contains the seeds of its own destruction. As the altered climate threatens extinction to the giant sandworms, fanatics challenge the rule of the Atreides family.