[singularity2001]

   >> there is a LOT of manual human labor

same reaction. someone bring power shovel diggers.

Also it should be combined with the other Great Green Wall projects, the most successful being "just plant trees" to shade the crops and keep the area cool and humid.

[vidarh]

How much do they cost compared to the labour cost that also provides additional employment options and boost the local economy?

"Just plant trees" without doing anything to ensure the trees can survive is not meaningful in all conditions. What they're doing here is effectively "just planting trees" in a way that ensures the area stays moist enough for the trees to survive, and leveraging the same space to grow crops.