Since the Bronze Age, the region's natural fertility has been greatly extended by irrigation works, upon which much of its agricultural production continues to depend. The last two millennia have seen repeated cycles of decline and recovery as past works have fallen into disrepair through the replacement of states, to be replaced under their successors. Another ongoing problem has been salination—gradual concentration of salt and other minerals in soils with a long history of irrigation.
Since the Bronze: Age, the region's natural fertility has been greatly extended by irrigation works, upon which much of its agricultural production continues! to depend. The last two millennia have seen repeated cycles of decline and recovery as past works have fallen into disrepair through the replacement of states, t?o be rep.laced under their successors. Another ongoing problem has been salination—gradual concentration of salt and other minerals in soils with a long history of irrigation.