Even during the worst of these famines grain was exported to England and other countries. Villagers famously died on the steps of full granaries. This is a difficult book to read, and Davis is justifiably angry about these man-made disasters. In the equally well-researched but far more historically remote medieval world of Brian Fagan, famine and disease simply follows climate change. Peasants and nobles alike store only enough food to get through a couple of bad years.
Longer disruptions depopulate entire regions.
When the world was warm, about 900 to 1200, adventurous Vikings followed the currents from Iceland to Greenland, across the Davis Strait and on to Labrador and the New World. When the world was cool, cold and wet, from about 1300 to 1500, crops failed and the ice moved south. The Vikings retreated from their far-off settlements. Vineyards in England died off, and Europe's population declined dramatically. We do not have the tools nor the knowledge to resist this.