From Iran to Iberia: character and evolution of sunken groundwater-harvesting agroecosystems in aeolian sand since Early Islamic times until today

By compiling and reviewing data on traditional sunken groundwater-harvesting agroecosystems in aeolian sand (SGHAS) in Iran, Egypt, Gaza Strip, Algeria and Iberia we analyze the motivation, function, crop-type and abandonment of recently excavated Early Islamic- to early Crusader-period (late 9th-mid-12th century) Plot-and-Berm (P&B) agroecosystems situated along the Mediterranean coast of Israel. The SGHAS and the Early Islamic P&B agroecosystems were affiliated with nearby towns. The SGHAS enrichened the sandy substrate with local organic material, while the Early Islamic sites used local urban refuse. The extensive long-term investment in earthworks to form SGHASs was proven profitable due to prime water security in the form of continuous shallow, ~0.6-2  m deep groundwater availability coupled with rainfall for agriculture and groundwater replenishment. The SGHAS crops are mainly a wide range of vegetable types, watermelons, date palms, and grapes.

The spotty appearance of SGHAS temporally lags after the abandonment of the Early Islamic P&B agroecosystems. They appear to have independently developed since the 15^th-16^th century until the 19^th-early 20^th century. These late/post-medieval to early modern times are characterized by an unprecedented growth in the variety of food and textile crop types due to the introduction of species from arid Muslim-controlled regions and from the newly discovered Americas. This convergence exemplifies the appearance of local ingenuities derived from growing agricultural and technological knowledge and experience, crop variety and pressing needs for capital and food security. Such engineering agriculture demonstrates entrepreneurship usually supported by local administrations.

Our finds do not support a successive spatial-temporal dissemination process since Early Islamic times as occurred for qanats in western Asia, Arabia, North Africa and Iberia. The Early Islamic agroecosystems were significantly ahead of their time, possibly explaining why they were never reestablished following their abandonment. This understanding implies that the Early Islamic crops were probably partly different from those of the later SGHAS counterparts and maybe also provided inedible, profitable crops like cotton. This study demonstrates the importance of traditional analogues for interpreting archaeological research gaps of past agricultural engineering landscapes and provides a focal point for reestablishing traditionally-based, community, and sustainable agricultures.