About 15% of the land is potentially productive, but agriculture, cultivating mainly hay, potatoes, and turnips, is restricted less than 1% of the total area. Fruits and vegetables are raised in greenhouses. There are extensive grazing lands, used mainly for sheep raising, but also for horses and cattle. Fishing is the most important industry. Aside from aluminum smelting and ferrosilicon production, Iceland has little heavy industry and relies on imports for many of the necessities and luxuries of life. More than half of Iceland's gross national product comes from the communications, trade, and service industries. Tourism is also important. The country has expanded its hydroelectric and geothermal energy resources to reduce dependence on oil imports, and roughly 90% of all homes are now heated by geothermal energy.
Fish and fish products, aluminum, animal products, ferrosilicon, and diatomite are the main exports; machinery and equipment, petroleum products, foodstuffs, textiles, and manufactured goods are imported. Most trade is with Germany, Great Britain, the United States, and the Netherlands.)