The Sahara is a complex ecosystem, like everywhere else (actually, it's a network of several deserts with different geographies, climates, and ecosystems). It's

The Sahara is a complex ecosystem, like everywhere else (actually, it's a network of several deserts with different geographies, climates, and ecosystems). It's not a dead place, and can't just be harmlessly stripped. That said, it's easier to make square sand round than round sand square. It's probably easier to crush rock into concrete-appropriate sand than to turn desert sand into concrete sand.