England had a diverse geography in the medieval period, from the Fenlands of East Anglia or the heavily wooded Weald, through to the upland moors of Yorkshire. Despite this, medieval England broadly formed two zones, roughly divided by the rivers Exe and Tees: the south and east of England had lighter, richer soils, able to support both arable and pastoral agriculture, while the poorer soils and colder climate of the north and west produced a predominantly pastoral economy. Slightly more land was covered by trees than in the 20th century, and bears, beavers and wolves lived wild in England, bears being hunted to extinction by the 11th century and beavers by the 12th. Of the 10,000 miles of roads that had been built by the Romans, many remained in use and four were of particular strategic importance—the Icknield Way, the Fosse Way, Ermine Street and Watling Street—which criss-crossed the entire country. The road system was adequate for the needs of the period, although it was significantly cheaper to transport goods by water. The major river networks formed key transport routes, while many English towns formed navigable inland ports.