The cuisine of New Zealand is largely driven by local ingredients and seasonal variations. As an island nation with a primarily agricultural economy, New Zealand yields produce from land and sea. Similar to the cuisine of Australia, the cuisine of New Zealand is a diverse British-based cuisine, with Mediterranean and Pacific Rim influences as the country has become more cosmopolitan. Historical influences came from British cuisine and Māori culture. Since the 1970s, new cuisines such as New American cuisine, Southeast Asian, East Asian, and South Asian have become popular. The Māori-language term kai refers to traditional Māori cuisine. When the Māori arrived in New Zealand from tropical Polynesia, they brought a number of food plants, including kūmara, taro, purple yam, hue and tī-pore, most of which grew well only in the north of the North Island. Kūmara could be grown as far south as the northern South Island, and became a staple food as it could be stored over the winter. Native New Zealand plants such as fernroot became a more important part of the diet, along with insects such as the huhu grub. Earthworms, called noke, are a part of the traditional Māori diet as well. Problems with horticulture were made up for by an abundance of bird and marine life. The large, flightless moa was soon hunted to extinction for food and tools as well. Rāhui, or resource restrictions, included forbidding the hunting of certain species in particular places or at certain times of year to allow populations to be maintained. Seafood consumed included kōura or freshwater crayfish, pāua or abalone, and tio or bluff oysters. Similar to other Polynesian people, Māori cooked food in earth ovens, known in New Zealand as hāngi, although the word umu is also used. Stones are heated by fire and food packed in leaves placed on top. These packs are then covered with foliage, cloth, or wet sacks, and then a layer of earth. Other cooking methods included roasting, boiling or steaming using geothermal heated water, and cooking over an open fire.