and lake Chad was a great inland sea.
I would proceed down a more conservative approach.
I would bioengineer grasses that could grow in the low moisture environment, stabilizing sand and trapping moisture.
There are tree-like plants in Australia that grow useful pulp and fiber, if I recall, that can live in very arrid conditions. I would use those as well.
I would seek to plant trees along mountain ridgelines to trap additional moisture.
I think the desalination stratgey has ineherent problems of cost and waste disposal of the massive amounts of salts and metals that would precipitate out.
While magnesium and sodium could be recovered economically, few others could.
I think if the bio-invasion strategy is pursued, it could over time build up biomass that would eventually change the weather patterns significantly.
There may be some aquifers with sweet water that could be tapped as well to irrigate intensive areas.
I think this kind of project could be awesome and world improving.
Ed