In the early 6th century, grape production in the Negev for the so-called "vinum Gazentum" ('Gaza wine' in Latin) experiences a major boom, due to the high demand for this product throughout Europe and the Middle East. This has been documented by studying ancient trash mounds at Shivta, Elusa and Nessana, which showed a sharp peak in the presence of grape pips and broken "Gaza jars" (a type of amphorae used in this period to export Levantine goods from the port of Gaza), following a slower rise during the fourth and fifth centuries. However, mid-century two major calamities strike the Byzantine Empire and large parts of the world: a short period of climate change known as the Late Antique Little Ice Age (536-545), caused by huge volcanic eruptions in faraway places, which lead to extreme weather events; and in the 540s the first outbreak of bubonic plague in the Old World, known as the Justinianic Plague. Probably as a result of these two events, international trade with luxury goods such as Gaza wine almost grounded to a halt, and in Shivta and other Negev settlements grape production again gave way to subsistence farming, focused on barley and wheat. The previously widely accepted theory that the Muslim conquest, which came a century later, and the Muslim ban on alcoholic beverages were the cause for the decline of the wine industry in the Negev has been now proven wrong. In nearby Nessana, the number of grape pips is even on the rise again during the Early Islamic period, probably due to the needs of a local Christian monastery. This seems to indicate that the wine industry of the Negev could well be sustained over centuries through appropriate agricultural techniques and in spite of the arid climate, but that the grape monoculture was economically unsustainable in the long run.