Without artificial drainage and flood protection, the Fens would be liable to periodic flooding, particularly in winter due to the heavy load of water flowing down from the uplands and overflowing the rivers. Some areas of the Fens were once permanently flooded, creating small lakes or "meres", while others were only flooded during periods of high water. In the pre-modern period arable farming was limited to the higher areas of the surrounding uplands, the fen islands and the so-called "Townlands", an arch of silt ground around the Wash where the towns had their arable fields. Though these lands were lower than the peat fens before the peat shrinkage began, the more stable silt soils were reclaimed by medieval farmers and embanked against any floods coming down from the peat areas or from the sea. The rest of the Fenland was dedicated to pastoral farming, fishing, fowling and the harvesting of reeds or sedge, for example for thatch. In this way, the medieval and early modern Fens stood in contrast to the rest of southern England, which was primarily an arable agricultural region.