Taming the Desert Pt. 2

So I was watching this video from the TED conference [It's a Think Tank], and I saw an idea for sand dune homes. Apparently you can actually make sandstone with bacteria and sand. The idea became this: Build a sandstone wall across the Sahara to create homes for the retreating natives, and to prevent the expansion of the desert with a wind breaker. Wind breakers stop the sand storms from expanding the desert, but they are usually cut down for firewood quickly. In order for this idea to work, we would have to plant thousands of trees along this wall in order to bring back the original environment of this area before the desert expanded. This would bring new life to these areas, by providing shelter, and a safe place to grow food again.