Plot-and-Berm (P&B) agroecosystems are traditional attempts to harness a 1–2 m deep groundwater for year-round agricultural productivity. Situated in sand bodies that comprise marginal/hinterland environments, these agroecosystems are based on sunken agricultural plots often between 2–8 m high berms, enabling easy hand/channel irrigation and root contact with groundwater. Refuse and/or organic material enrich and stabilize the plot and berm sand. The earliest agroecosystems, along several Mediterranean coastal dunefields of Israel, date to the Early Islamic period (9th/10th–early 12th centuries CE). This initiative is probably mawāt (Arabic: “dead”)—reclamation of marginal lands. Traditional P&B agroecosystems in Iran, the Mediterranean coast of northeastern Sinai, Algerian Sahara, and Iberian Atlantic coast sustain a wide and differing mixture of fruit trees, melons, vines and vegetables and are of geoheritage value. Each of these agroecosystems possess several distinct attributes and some historically date back to the Middle Ages. This paper proposes two hypotheses concerning the origin of these agroecosystems.