Traditional willow growing and weaving (such as basket weaving) is not as extensive as it used to be but is still carried out on the Somerset Levels and is commemorated at the Willows and Wetlands Visitor Centre. Fragments of willow basket were found near the Glastonbury Lake Village, and it was also used in the construction of several Iron Age causeways. The willow was harvested using a traditional method of pollarding, where a tree would be cut back to the main stem. During the 1930s more than 3,600 hectares (8,900 acres) of willow were being grown commercially on the Levels. Largely due to the displacement of baskets with plastic bags and cardboard boxes, the industry has severely declined since the 1950s. By the end of the 20th century only about 140 hectares (350 acres) were grown commercially, near the villages of Burrowbridge, Westonzoyland and North Curry. The Somerset Levels is now the only area in the UK where basket willow is grown commercially.