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 i