Question about Roman subjugation area

[pockettank]

well what i wanna know is why the area around carthage is 100% desert cuz i heard somewhere a while ago where they found aqueducts and highways in the northernmost part of where the Sahara is today because it was a fertile area and the romans used it until the desert grew over top there abondened citys after the fall of the romans in that area

EDIT: sorry about it being off topic.. i was just wondering

[Sakkura]

well what i wanna know is why the area around carthage is 100% desert cuz i heard somewhere a while ago where they found aqueducts and highways in the northernmost part of where the Sahara is today because it was a fertile area and the romans used it until the desert grew over top there abondened citys after the fall of the romans in that area

EDIT: sorry about it being off topic.. i was just wondering

It isn't all desert AFAIK. Wherever your armies can move are certainly not desert because that was pretty much off-limits for armies in antiquity.