Can deserts be made habitable?

Yes, many ideas, but one interesting one that applies to deserts close to seas, is the "seawater greenhouse" https://www.youtube.com/watch? read more

Deserts are already sustainably habitable, at low population densities. Deserts can be made habitable for a while at high population density by using water supplies unsustainably - e.g. Las Vegas. read more

Note that deserts on Earth are caused by the air circulation not delivering much rain there. A desert planet would be one in which there was little water overall. In the case of Dune, the sand-trout have supposedly locked away all of the water. read more