So at the end of God Emperor of Dune

Leto is dunked in the river. This causes his sand trout skin to disperse, shortly resulting in his death. There are lots of references in the book to this meaning the planet will revert to desert because the sand trout will encapsulate all the water.

But why?

Why would the planet-full of sand trout that existed at the end of the first book not have kept the planet arid, if something-in-the-range of a few tons could convert it back to dry sand? What is so special about these sand trout that they can do what the much larger number could not do?

  • 1
    Y'know when I was a kid, I literally never even noticed this kind of thing. I guess I just figured it's all magic, who's to say what works?
    – DavidW
    Commented Jan 19, 2023 at 16:14

3 Answers 3


They're all gone, except those being the skin of Leto. It's not explicitly stated, but there are two potential reasons the sandtrout disappeared.

As you know, the planet Arrakis was now a verdant lush place full of life. The only place where desert remained was Leto's Sareer, the little desert, 1,500 by 500 km. It's not explicitly stated in the book during either Children of Dune or God Emperor of Dune in precise terms how this came to be - however the first novel, Dune itself alludes to a possible mechanism.

1 - The Planet would no longer support the lifecycle of the worm and they just died out:

Even before Leto's reign, there was open water on the face of Dune because of his father's reign and choices.

Firstly, the worms-sand was shrunk by the application of technology, Leto's weather-control satellites, which he also employed to maintain the dryness of The Sareer (somewhat imperfectly). The number of worms dwindled and the reproductive lifecycle of the worms was disrupted.

They could have naturally died out.

2 - He poisoned them with the Water of Death.

In the first book, the scene after Paul's transformation by the spice essence gives away a possible mechanism:

Paul took a deep breath, said: “Mother, you must change a quantity of the Water for us. We need the catalyst. Chani, have a scout force sent out … to find a pre-spice mass. If we plant a quantity of the Water of Life above a pre-spice mass, do you know what will happen?”

Jessica weighed his words, suddenly saw through to his meaning. “Paul!” she gasped.

“The Water of Death,” he said. “It’d be a chain reaction.” He pointed to the floor. “Spreading death among the little makers [immature/larval sandworms], killing a vector of the life cycle that includes the spice and the makers [mature sandworms]. Arrakis will become a true desolation—without spice or maker.”

Chani put a hand to her mouth, shocked to numb silence by the blasphemy pouring from Paul’s lips.

“He who can destroy a thing has the real control of it,” Paul said. “We can destroy the spice.”

There is no doubt that Leto's vast stockpiles of the spice and the Guild and his prescience keeping out the smugglers, gave Leto a monopoly on the spice.

To consolidate his hold once the worm-presence and spice production had dwindled to negligible amounts, to catalyse the reaction for himself, to make his body with its sandtrout skin the most precious thing in the universe. This would naturally fit quite comfortably with his religious pretensions.


The only thing needed to convert Arrakis into a new Dune locking-up all the water again allowing worms to roam is sandtrout, any sandtrout. The only extant sandtrout were those enclosing the body of the God Emperor.


So this is pure conjecture as it does not reference the books (AFAIK); but at the time of the planet full of sand trout, the Fremen had collected the vast majority of the world's water within Qanats which was then subsequently released with the newly installed weather satellites/control. I would assume the entire surface was essentially flooded beyond the ability of the sand trout to manage and they drowned (it is mentioned in the books that children would drown the sand trout when they were caught).

Move forward 3000 years and the planet has stabilised with respect to the water lifecycle and the God Emperor is killed at/close to the Sareer which is the last remaining desert. This would allow the sand trout a ground to expand from gradually encapsulating everything until Dune was once again a desert planet. Here there wouldn't be enough water available to once again kill them all in one go.


I'm somewhat confused by your question: "Why would the planet-full of sand trout that existed at the end of the first book not have kept the planet arid, if something-in-the-range of a few tons could convert it back to dry sand? "

Arrakis WAS --past tense -- arid in Dune. (See, for example, the massive Fremene culture that developed around moisture.) The ruling house (whether Atreides or Harkonnen; the condition was the same under both) paid exorbitant sums to import water to the planet in order to support life in the cities. The sandtrout/sandworm ecosystem was well-established, and all those sandtrout are out there "doing their thing" (witness Liet Kynes' death) to keep the positive feedback loop running.

By the time of God Emperor of Dune, sandworms are all but extinct. Millenia of terraforming under Leto and his subjects had made Arrakis too moist, and the long-and-short of it is that the remaining sandworms are sickly (no quote handy; book in a box at the moment) and the sandworm/sandtrout ecosystem equilibrium has been all but destroyed.

Leto's plan is for each sandtrout to carry a "pearl of consciousness" that somehow lets the sandtrout adapt to their new environment, allowing the sandtrout to once again encapsulate and sequester all the open water and revert Rakis/Arrakis back to a global desert.


It works.

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    OP isn't saying that Arrakis wasn't arid at the start. On the contrary, he is saying that it was arid, and then was converted (by Leto) to wet, despite the fact there were potentially billions of sandtrout. How did all those sandtrout fail to keep it arid, but the (relatively) few that came from Leto's death managed to convert it back? Commented Jan 19, 2023 at 15:33
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    They weren't importing water, they were collecting it from the poles
    – Valorum
    Commented Jan 19, 2023 at 20:00
  • Only answer that mentions the "Pearl of Consciousness" that Leto was leaving the sandtrout, perhaps should emphasize this more. Both the sandtrout and the worms would be "smarter" after Leto's sacrifice, better able to overcome human resistance/terraforming.
    – antlersoft
    Commented Jan 28, 2023 at 20:34

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