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 geo-heritage 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.