Kalimantan contains Indonesia's greatest expanse of tropical rain forests, including valuable stands of camphor, sandalwood, and ironwood, and many palms. The thick jungle and myriad insects tend to discourage large-scale agriculture, but rice, sago, tobacco, millet, coconuts, pepper, sweet potatoes, sugarcane, coffee, and rubber are grown. In 1983, over 13,000 sq mi (20,917 sq km) of rain forest were destroyed by fire, causing enormous damage to the ecosystem, and immigration from other, heavily populated parts of Indonesia, combined with illegal logging, has resulted in increasing deforestation, threatening the orangutan, the pygmy elephant, and other species. Kalimantan contains some of Indonesia's most productive oil fields (discovered in 1888). Coal has been mined there for more than a century, and gold since earliest times. In 1995 one of the richest gold deposits in the world was discovered in NE Kalimantan. Other mineral resources include industrial diamonds, bauxite, and extensive reserves of low-grade iron ore, which are, however, little exploited.