[mywittyname]

> If you want to fight desertification, then you must combat evaporation first,

This is something plants can be remarkably good at!

I don't think you can get around irrigation to bootstrap the process. We could probably begin the process by putting down some irrigated top soil, and laying a bio-degradable, transparent moisture barrier to keep the water from evaporating while the ground cover grows.

Alternatively, I'm sure we could construct a man-made river running through a desert to revitalize it. I'm not a geologist, but I suspect that the existence of an active river is a strong influence on whether a region becomes a rain forest or a desert.